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820 User Manual

1. Q5 Q TITLE MEASUREMENT TITLE Q6 Q TIME CURRENT TIME Q7 Q DATE CURRENT DATE Q8 Q DAY DAY OF WEEK Q9 Q BAUD COMI BAUD RATE Q10 Q SADDR COMI ADDRESS Q NI RESERVED PARAMETER Q12 Q HS COM PORT HANDSHAKING REGISTER Q13 Q NI RESERVED PARAMETER Q14 Q LOGIC1 OUTPUT 1 LOGIC unused 015 Q OUTITIM OUTPUT 1 HOLD TIME unused Q 16 Q LOGIC2 OUTPUT 2 LOGIC 017 Q OUT2TI OUTPUT 2 HOLD TIME unused 18 Q HALT HALT LINE MODE Halt Line Mode Q18 has a None state available This allows systems with intrusion alarm hardware to be disabled during servicing The choices are None Pause Toggle Level Alarm The Model 820 dials out when in the Modem Mode and remaining memory gets below 5000 bytes It now uses RMS Threshold 2 to dial out on EXCD events Q19 Q BEEP BEEP WHILE RUNNING unused Q 20 Q PWRSV POWER SAVE OPTIONS 021 Q TIMMD TIMER MODE Q22 Q RUND TIMER RUN DATE Q 23 Q STOPD TIMER STOP DATE 024 Q RUNTI TIMER RUN TIME 1 Q25 Q STOPTI TIMER STOP TIME 1 Q26 Q RUNT2 TIMER RUN TIME 2 Q27 Q STOPT2 TIMER STOP TIME 2 Q28 Q LKCOMB LOCK COMBINATION B 16 Model 820 Technical Reference Manual Q29 Q LKRS LOCK R S KEY 030 Q LKSU LOCK SETUP Q31 Q LKFN LOCK FUNCTION Q32 Q LKRES LOCK RESET Q 33 Q LKPWR LOCK THE ON KEY 034 Q LKIO LOCK I O 035 Q CALL
2. 7 14 Overview Model 820 2 1 Parameter 13 14 Character naroa tian B 14 character strings B 12 Daily History 7 14 DOSE i esi ease 8 13 7 8 8 14 Exceedance History 8 14 exceedance history 7 9 exceedance level 7 8 indexed B 12 Interval history 7 5 key access 8 1 Index Model 820 1 2 numeric 0 12 10 1 eae 15 SEWING i 12 setting and viewing 7 1 setting 4 1 system 1 20 8 7 template 12 Time History Data 7 3 Hep 8 10 Parameters Additional System Functions 152 154 101 8 19 changing 8 3 Lmax Lmin esee 5 5 locating ei recedere 8 2 Model 820 Chapter 8 8 1 time 7 1 asSDy ote ea Op itd 7 13 diagram 7 13 setting functions 7 12
3. 8 12 7 lE n 5 4 i e C 18 Weightings A and GC oes 5 4 Index Total Customer Satisfaction Guaranteed ARSON DAVIS 3425 Walden Avenue Depew NY USA 14043 Phone 716 926 8243 Toll Free 888 258 3222 A PCB PIEZOTRONICS DIV LarsonDavis com FAX 716 926 8215
4. 1 7 Block Diagram issue sese eee RU epe 1 10 Getting Started iv ee es 1 11 Unpacking and Inspection 1 12 ACCESSO Silano irinae EE AE EAE OE 1 12 Optional Equipment ue Ie Rae te eit 1 13 Battery Installation eee HERREN cR 1 17 Environmental Considerations 1 18 Preparing to Use the Model 820 Connecting the 1 18 Overview to Model 820 2 1 Understanding the Model 820 2 1 Getting to Know Screen Symbols sse 2 8 Understanding the Model 820 2 9 Turning On the Model 820 2 9 Checking the Battery Voltage sss eene 2 10 Turning Off the Model 820 eR Seba itis 2 11 Calibration 3 1 Calibrating the Model 820 3 1 Quick Start 4 1 Setting Parameters Using Function Keys 4 1 Setting Parameters Using Numbers and Other 4 3 Setting Time Date and Day 4 7 AC DC Output 4 8 Performing a Measurement Reading the Data 5 1 Taking nnne nnns 5 1 SEM 5 1 LinaxsLEmin etit eoe oo ied OO wees 5 5 Cha
5. 1 5 2 2 1 2 2 1 parameters 1 2 Performing Measurement 1 2 Quick 1 2 Specifications App 1 Timed Measurement 1 2 2 3 1 1 answering procedure B 35 control B 34 dial out B 34 monitor numbers B 34 phone dialing procedure B 35 Modify KEY eftt e bote 2 7 parameters 8 3 N Near Field Index ACOUSTIC eres 11 geometric C 11 glossaty 11 Noise 2 C 12 12 22 Daily History 7 15 daily personal exposure C 3 dose D iiie eee C 12 2 12 MOOK iet tee 22 glossary d eene ees C2 C 11 DINK sei ees bisa DEA as C 12 projected noise dose C 13 single event exposure level SENEL Lax EE C 13 Mcr C 12 Numeric Parameters B 12 O DUO Mal accipe doi tene 1 13 OSHA rete ee etat C 12
6. A 4 Reference Level eee ce hec 4 Frequency Weightings cete ae ORI dk Shee E Es A 4 Detector Time A 7 Effects of Temperature secre roce ipeo weg e ttes A 7 Etfects of Humudly eR P A 7 Limits of Temperature and A 7 Microphone Extension 1 2 440200 4 01040060000000000000000000000000000000004 A 7 Instrument Observer Positioning for Best A 8 AC and DC Outputs eere eot ew ee naris A 8 AGC Output ida EE EPOR RECETAS A 8 nM A 8 Reference Frequency oue aemper quiae dete os A 8 Stabilization Time ice eme UHR TE Oe eed A 9 Microphone Electrical Impedance 2 1 2000204000 00000000000000000000040000503 A 9 Functions Measured sce eee eU E als A 9 Data Stora ge A 9 Data Communications rene A 10 Digital Display einen o Remate eiteoinidbad i indem A 10 Digital Display Resolution A 10 Display Bargrapb oe e Ap eite ae A 10 Real time Clock Calendar sess enne A 10 Run time eie i MER EGER eee 11 Standards Met ie a Rte RE RE D A ees 11 CE Information eee eee dee deed 11 Power Supply xeren te SR RR e he I E O
7. 8 5 Remote control Serial Port 1 2 Report DING 10 1 Reports 10 3 Reset KOY 2 4 IRESET ALE otn 8 1 S322 92 ane vasi 1 6 data communications A 10 RS 232 5 8 8 RS 232 interface B 1 Run Log Variables B 29 Run Stop 2 4 S Screen Symbols eiie end 2 8 SEL My RUE 2 6 Serial 1 12 Serial Port ADD Ges sit eite 1 2 Setup enter and 8 1 2 3 recalling 2 5 oin 8 6 Storing rr 8 5 Setup Parameters 8 7 SIUE escoger tubes das 2 3 oed eene 2 4 tih EA 5 1 M 2 5 SLM Sound Level Meter 8 11 Sound average level lavg C 1 day night average level C 3 energy average Leq C 16 2 13 exposure 14 fixed 15 glossary esee C 13 impulsen C 16 instantaneous C 15 intensity l esee C 17 moving C 15 222 14 sound pressure le
8. 5 7 8 17 2 5 Phone 35 2 Pin configurations B 2 1 5 5 Power ac dc 4 8 1 1 17 external i 1 17 1 18 Internal Leve 1 17 Model 820 1 18 12 Power Save 8 9 1 18 Preamplifier 13 2 3 8 18 Chapter 10 1 2 5 31 daily 8 19 normal printout parameters 10 1 Printing a 10 1 real time 10 4 DON 10 3 R RAM registers 8 6 Real time printing 10 4 Reference Direction 2 Reference 8 12 specifications 4 Register RAM 8 5 Register
9. 7 8 Exceedance History 8 14 Exchange 8 12 910 C 6 Exchange Rate Factor QIOSSANY rete 6 Exposure Factor 91058 C 6 F 6 ACOUSIIG 6 C 6 Features ononon 1 5 Model 820 1 5 Formatting 1 3 1 3 Free C 6 Frequency band pass filter C 7 glossary eese dern C 6 Hz rad sec tes C 7 Frequency Weightings specifications A 4 Frequency weightings 1 5 Functions additional system 8 19 aj 7 1 setting and viewing 7 1 time history 7 1 Functons PASSDY 7 12 G Glossary 1 2 Histogram 30 Histogram Reports B 19 History commands eee B 4 8 14 History Functions Chapter 7 7 Interval 8 15 2 4 records 24 8 16 History Fun
10. 300 19200 Baud rate of the serial interface Serial printer or computer rate should be the same 10 RS 232 Address 0 127 Enables addressed communication mode for a network of Larson Davis SLMs Each must have a unique address Normally only one Model 820 is used thus the address should be set to 0 to disable 12 COM Ports Hand shaking Register None Hdwr XOFF Both Serial handshaking protocol Model 820 SW1 uses None Note To con serve power the Model 820 turns off the serial port after 255 sec of non use To keep unit on and connected an external power supply must be used 8 8 Model 820 Technical Reference Manual 14 Output 1 Logic Off RMS R PEAK P R P INTV D R I R P I A D R A P A R P A I A R I A P I A R P I A R S True takes it to 5 volts When set to Off is DTR Indication that Interval started and will stay on time set in parameter 15 Logic control including A are not applicable to the Model 820 Run Stop 15 Output 1 Timer enter time There are 2 modes to the Logic Out put Time now If the time is set to 5 sec or less it is assumed to be a mini mum time and the output will be asserted for a minimum of the time selected If the time is programmed to be greater than 5 sec then the time is considered to be the maximum dura tion that the pulse should last and the output will be asserted for
11. Model 820 Technical Reference Manual C 15 rms L 20 Lp E 2010810 Prms 10 where po is reference sound pressure of 20 The square of the sound pressure is a power like quantity that can be expressed in the original form of the level definition 2 Prms 2 2 1 10 L gt 2 Prms pol0 Po Sound Pressure Level can be converted to sound pressure as fol lows If the sound pressure is 1 Pascal then the sound pressure level is 2010 2log 50000 20 4 699 94 048 20 10 Calibrators often use a level of 94 dB so they generate a sound pressure of 1 Pascal If the sound pressure level 76 3 dB then the sound pressure is 6 76 3 20 20 10 e10 3 815 6 2 185 20 10 20 10 20 0 0065 0 13 Energy Average Leg The value of a steady sound measured over a fixed time period that has the same sound energy as the actual time varying sound over the same period This descriptor is widely used It is a fixed average See Sound Pressure Impulse The value of an impulsive sound The reading will depend on the time weighting applied Unweighted Peak The peak value of a sound with a meter that has flat frequency weighting and a peak detector Model 820 Technical Reference Manual Sound Power W Weighted Peak The peak value of a sound with a meter that has a frequency weighting other than flat and a peak detector The sound power emitted by a sound source
12. UWPK HISTOGRAM TABLE HI VALUE n Q 103 Q PRN UWPK HISTOGRAM TABLE RESOL x Tailored Report Q 104 Q PRN EXCD REPORT x Q 105 Q PRN EXCD REPORT LOW RECORD n Q 106 Q PRN EXCD REPORT HIGH RECORD n Q 107 Q PRN INTV REPORT x Q 108 Q PRN INTV REPORT LOW RECORD n Q 109 Q PRN INTV REPORT HIGH RECORD n Q PRN HIST REPORT x Q PRN HIST REPORT LOW RECORD n Q 112 Q PRN HIST REPORT HIGH RECORD n Q 113 Q PRN DAILY NOISE REPORT x Model 820 Technical Reference Manual Q 114 120 RESERVED PARAMETER 18 24 respectively Q 121 150 Reserved Miscellaneous 151 Q AUTOLEQ AUTO SEND HISTORY LEQ TO PRN unused Q 152 Q EAON ELECTROSTATIC ACTUATOR OFF ON Q 153 Q HEATER HEATER LINE OFF ON unused Q 154 Q MDMMD MODEM MODE x Q 155 Q DIAL MODEM DIAL OUT MODE x Q 156 Q PHONE MODEM PHONE NUMBER 30 char Q 157 Q MONNUM 20 20 Q 158 Q MDMI MODEM INIT STRING 30 char Q 159 Q PWRMD POWER MODE Normal Ext CO Q 160 Q PWRCO EXTERNAL POWER CUT OFF VOLTAGE Q 161 Q TMEXPR TIMED EXCD PERIOD Special Functions Advanced use only Remaining commands are not available on SETU P menu Q 162 167 Q NI18 23 RESERVED PARAMETER 18 23 Q 168 Q RTEXCD REAL TIME EXCD REPORT x Q 169 Q RTINTV REAL TIME INTV REPORT x 170 Q RTHIST RE
13. Other Read Commands Sound Exposure E is calculated and displayed in pascal squared hours as needed in some of the European Countries This value is read with the R162 command and is available in the top line of the DOSE a display The formula used is E T 10 Leq 10 20uPa where E is the Exposure T is the elapsed time in hours and 20 is the reference sound pressure 20 micro pascal squared R 163 TAKT3 Takt Maximal 3 Second nnn n dB R 164 _TAKTS Takt Maximal 5 Second nnn n dB Group Read Programming The group read command GO and the O ther 3 command return the values of a list of up to 8 read variables previously defined by the programmer Code Description Response OI Read SLM data nnn n nnn n nnn n nnn n lt CR gt lt LF gt R 4 SPL R 11 TWA R 17 Lmin R 21 Lmax lt CR gt lt LF gt 02 unused unused variable 03 Read Group of R variables pro grammed by G n r 04 Read 8205 LCD Display each line sep arated by lt LF gt Syntax Response G0 or 03 er values of variables separated by commas In order to define the variables read by group read commands use the following command for each desired read variable Syntax Response G roup n var no cr If Model 820 Technical Reference Manual B 11 Where n is from to 8 indicating the group list index and var_no is the number of the R v
14. The hour minutes and seconds are entered in that order and are separated by Military 24 hour clock time is used i e add 12 to afternoon hours Syntax Response S et item number hh mm ss cr If Example S24 14 25 33 sets Timer Run Time 1 to 14 25 33 B 14 Model 820 Technical Reference Manual Query Parameters All these commands begin with Q Brackets indicate optional characters and operands See Chapter on SETUP for a list of all the parameters and their settings cr carriage return If line feed space Syntax Response Q uery item_number flag Depends on flag Option flags elicit the following responses Flag Response none Current parameter 1 Parameter name and current setting 2 Current parameter setting including spaces in brackets or parentheses 3 Parameter name and current setting including spaces in brackets or parentheses 32 Index number for indexed parameter Flag values may be added together for desired combinations Example Response 1 Q66 No 2 066 1 Excd History Enable No 3 Q66 2 _No 4 Q66 32 0 5 Q66 3 Excd History Enable _No Responses are denoted by x if Yes No or n if numerical Q1 Q RESALL RESET ALL Q2 Q HDGI HEADING LINE 1 Q3 Q HDG2 HEADING LINE 42 Q4 Q HDG3 HEADING LINE 43 Model 820 Technical Reference Manual B 15
15. sent a lessened tolerance for noise during evening activities They are energy summed and converted to an average noise exposure rating Model 820 Technical Reference Manual Criterion Duration T It is the time required for a constant sound level equal to the Crite rion Level to produce a Noise Dose of 100 Criterion Duration is typically 8 hours Example If the Criterion Level 90 dB and the Criterion Duration is 8 hours then a sound level of 90 dB for 8 hours will produce a 100 Noise Dose See Noise Dose Standard ANSI 512 19 Criterion Sound Exposure CSE The product of the Criterion Duration and the mean square sound Criterion Sound Level L pressure associated with the Criterion Sound Level when adjusted for the Exchange Rate It is expressed in Pascals squared seconds when the exchange rate is 3 dB where q is the Exchange Rate Factor See Exchange Rate L q CSE 10 Standard ANSI 81 25 It is the sound level which if continually applied for the Criterion Duration will produce a Noise Dose of 100 The current OSHA Criterion Level is 90 dB Standard ANSI 12 19 Daily Personal Noise Exposure It is the level of a constant sound over the Criterion Duration that contains the same sound energy as the actual unsteady sound over a specific period The period is generally shorter so the sound energy is spread out over the Criterion Duration period Example If the Criterion Duration 8 hou
16. 0 255 RMS Histogram highest printed level 95 Histogram Resl 1 8 1 2 1 0 2 0 5 0 10 Spacing in dB between histogram entries 96 Peak Histogram No Yes Prints histogram of overall peak lev els 97 Lowest Level 0 255 Peak Histogram lowest printed level 98 Highest Level 0 255 Peak Histogram highest printed level 99 Histogram Resl 1 0 2 0 5 0 10 Spacing in dB between histogram entries 100 UwPk Histogram No Yes Prints histogram of overall unweighted peak levels 101 Lowest Level 0 255 UWPk Histogram lowest printed level 102 Highest Level 0 255 UWPk Histogram highest printed level 8 18 Model 820 Technical Reference Manual 103 Histogram Resl 1 0 2 0 5 0 10 Spacing in dB between histogram entries 104 EXCD Report No Short Long Prints exceedance report 105 Lowest Rec 0 65535 Starting exceedance record number of printout 106 Highest Rec 0 65535 Ending exceedance record number of printout 107 INTV Report No Short Long Prints interval report 108 Lowest Rec 0 65535 Starting interval record number of printout 109 Highest Rec 0 65535 Ending interval record number of printout 110 HIST Report No Yes Prints time history report 111 Lowest Rec 0 gt 999999 Starting history record number of printout 112 Highest Rec 0 gt 999999 Ending history record number of printout 113 Daily Report No Short Long Prints
17. 1 second constant Fast exponential avg 1 8 second constant Impl impulse response For OSHA measurements this is normally set to Slow For environ mental measurements Fast or Slow may be used Within a given period of time the Fast detector will take more measurements than the Slow Therefore the Fast detector is likely to measure more higher and lower levels than the Slow detector The A and C weightings simulate human hearing response and meet Type 1 precision standards for accuracy Flat no weighting allows the signal to pass through 5 4 Taking a Measurement Model 820 Technical Reference Manual Step 4 The Model 820 has been preset at A To change the setting press gt to the preferred setting and Enter Step 5 Find item 41 by pressing x AC Out Weighting which has the values listed here Choose one by pressing Flat Whgt F 20 W 20 Step 6 Item 42 UwPk Weighting press the v again Chose from the values listed with gt Flat C Step 7 Item 43 Mic Polarization was touched upon earlier Step 8 Press to exit setup mode We have already looked at the Limax and Lmin in a previous screen These values are also available directly from display keys They can be accessed while the unit is taking a measure ment or in the stop mode Only when the unit is running is the data recorded These measurements are usually read after they have been taken and the measurement
18. 6 6 To turn on the Lock press v and gt keys When Yes appears press Enter If you should wish to unlock the system for further input or readings press GHIFT and 85 then If you choose to use this feature enter something you wont forget i e a name or birth year and press Enter These setup items control whether or not the lock feature will work for that particular function For example if Yes is entered for Lock Setup then the R S and other func tion can be used when Setup Lock function is implemented Press v to see other functions that can be locked See chapter 8 parameters 28 34 Notice that as you enter your code only appear to protect your password Again make the password easy to remember should you wish to use this function Enter your password code and press Enter The Model 820 is now unlocked and accessible for additional entries Setting the Password Lock to Protect Settings Model 820 Technical Reference Manual History Functions The process of measuring and recording units of sound and retrieving the data for study and understanding is enhanced by additional functional capabilities of the Model 820 Sound Level Meter This chapter will cover Setting and Viewing Advanced Functions Time History Time History Data Log and Data Interval History Interval History Data Exceedance Setting PassBy functions Dealing wit
19. It is measured in Watts Sound Power Level PWL L The logarithmic form of sound power It is also expressed by attach Sound Speed c ment of the word decibel to the number The logarithm is taken of the ratio of the actual sound power to a reference sound power which is 1 pico watt Sound power level cannot be measured directly but can only be deduced through measurements of sound intensity or sound pressure around the source The equation for it is L w 10 0 The speed at which sound waves propagate It is measured in meters per second It should not be confused with sound or particle velocity which relates to the physical motion of the medium itself c 20 05 degC 273 m sec 49 03 degF 460 ft sec Spectrum Frequency Spectrum The amplitude of sound or vibration at various frequencies It is Threshold Sound Level Lt given by a set of numbers that describe the amplitude at each fre quency or band of frequencies It is often prefixed with a descriptor that identifies it such as sound pressure spectrum It is generally expressed as a spectrum level The A weighted sound level below which the sound produces little or no Noise Dose accumulation and may be disregarded It is used for hearing damage risk assessment Standard ANSI 51 25 Time Weighted Average Sound Level TWA It is the level of a constant sound over the Criterion Duration that would expose a person to the sam
20. Model 820 Technical Reference Manual R36 _PSECNT Number of PAUSES nnnnn R37 _PTIME PAUSE Time OFF not inc hhhhh mm ss R38 Ln 1 nnn n dB R39 _LN2 Ln2 nnn n dB R40 _LN3 Ln3 nnn n dB R41 _LN4 Ln 4 nnn n dB R42 _LNS Ln 5 nnn n dB R43 _LN6 Ln6 nnn n dB R44 _O DOSE Overall Dose nnnnn n R45 _C DOSE Current Dose nnnnn n R46 _O PROJ Overall Projected Dose nnnnn n R47 _C PROJ Current Projected Dose nnnnn n R48 _LDLDOSE LDL Dose nnnnn n R49 _LDLPROJ LDL Projected Dose nnnnn n R50 _LDLLINT LDL Lint nnn n dB R51 _LDLSEL LDL SEL nnn n dB R52 _LDLXR LDL Exchange Rate Text R53 _LDLVALID LDL Valid display see note below 54 RELLVL Last Level Relative to REFLVL nnn n R55 TABLE Display Histogram Selected ccc R56 COUNT Display Overall Count nnnnnk R57 _O LEQ Overall Leq nnn n dB R58 _D LEQ Daily Leq nnn n dB R59 _H LEQ Hourly Leq nnn n dB R 60 h _HNL Hourly Leq 0 23 nnn n dB HNLPART Hourly Leq partial indicator nnn n dB R62 _O LDN Overall LDN nnn n dB R63 _D LDN Daily LDN nnn n dB 64 _H LDN Hourly LDN nnn n dB R65 _O CNEL Overall CNEL nnn n dB 66 _D CNEL Daily CNEL nnn n dB Model 820 Technical Reference Manual B 7 R67 _H CNEL Hourly CNEL nnn n dB R68 _EXLEQ Total EXCD Leq nnn n dB R69 _EXTIM Total EXCD Time hhhhh mm ss s NOTE An LDL Logged D
21. Step 6 To exit the setup mode press Setting Parameters Using Numbers and Other Characters The Model 820 has the ability to show 3 lines for your Com pany Name and one line for the Measurement Title which is used on the reports These parameters are entered from the keyboard Through the keyboard you can enter all of the capital letters from A to Z the digits 0 to 9 and some punctuation charac ters There are three levels of functions when in the Alpha Parameter Modify Mode The charts below Figures 4 1 to 4 4 show the characters that are available They are listed according to the number of times you consecutively press the key The shift indicator in the lower right corner of the instrument s display will show the number of times the key has been pressed by showing the letter n and S then 2 and 3 respectively for 0 to 3 presses Figure 4 1 Standard Alpha Numeric Keyboard Layout This panel is available without pressing the shift key or the equiv alent of 0 presses Model 820 Technical Reference Manual Setting Parameters Using Numbers and Other This panel is accessed by pressing the shift key one time The S will appear in the lower right corner of the display indicating this panel is accessed This panel is accessed by pressing the shift key two times The number 2 appears in the lower right cor ner of the display indicating this panel is accessed This final panel is access
22. 10dB NOTE The mode is always turned off with a CAL Change Q 208 Q NFMODE NOISE FLOOR COMP MODE Q 209 Q 875MD 875 RTA MODE None Excd Intv Dual unused Q 210 Q CNTLREG AUX CONTROL REG 211 Q EXREC EXCD RECORD NUMBER Q212 Q IVREC INTV RECORD NUMBER Q213 Q HSTREC HIST RECORD NUMBER Q214 Q LOGREC RUN LOG RECORD NUMBER Q215 Q DYREC DAILY RECORD NUMBER B 22 Model 820 Technical Reference Manual Q 216 Q CALREC CALIBRATION RECORD NUMBER Q217 Q TBLLVL LOCATE HISTOGRAM TABLE LEVEL Q 218 225 Q NI42 Q N149 RESERVED PARAMETER 42 49 respectively Q 226 Q OVLDLVL OVERLOAD LEVEL Q 227 Q RMSOS RMS CALIBRATION OFFSET Q 228 Q PKOS PEAK TO RMS CAL OFFSET Q 229 Q UWPKOS UwPk TO RMS CAL OFFSET Q 230 231 Q NI51 Q N152 RESERVED PARAMETER 51 52 Q 232 Q TEMP ENTER CURRENT TEMPERATURE Q 233 Q SERNUM ENTER SERIAL NUMBER Model 820 Technical Reference Manual B 23 History Records The various histories of the Model 820 are accessed in a simi lar fashion After using a direct index to the correct record one can advance or back up a certain number of records to the new value to be read Brackets in the syntax indicate optional characters and oper ands cr carriage return If line feed Types of History Denoted in syntax by history_no 1 Exceedance E 2 Interval 3 Daily D 4 Run Log L 5 Calibration C 6 Time H 7 Histogram Ta
23. 20 kHz up to a 12 foot micro phone extension cable may be used with the Model 820 Model 820 Technical Reference Manual Detector Time Weightings A 7 Instrument Observer Positioning for Best Measurements Measurements can be made with the Model 820 held in one hand with the arm extended away from the body however better measurements can be made with the Model 820 placed on a tripod AC and DC Outputs The output impedance is 600 for both the AC and DC out puts of the Model 820 For minimal error use instruments with S 100 k input impedance when making AC or DC output readings AC Output Output Impedance 600 34 Gain 0 dB or 20 dB User Selectable Measurement Range 88 0 dB DC Output Output Impedance 600 34 Scale 20 mV dB Measurement Range 105 0 dB Voltage Range 0 to 3 volts Temperature Coefficient 936 n V C Reference Frequency The reference frequency is 1000 Hz A 8 Instrument Observer Positioning for Best Measurements Model 820 Technical Reference Stabilization Time The Model 820 will not proceed to a running condition until it is allowed to stabilize At power on with the polarization volt age set to 200V or 28V the stabilization time is approximately 45 seconds With the polarization voltage set to OV the stabili zation time is approximately 10 seconds A shorter stabiliza tion time is also invoked when certain settings Weighting Detector etc are changed Mic
24. 24 Ln 6 nnn n dB 101 ntv Variables 1 24 Macro Model 820 Technical Reference Manual B 27 Daily History Variables D1 D102 Brackets in the syntax indicate optional characters and oper ands Syntax Response D aily var no hour daily var Example 05 5 hourly noise level for hour 5 to 5 59 59 a m DI Date ddd ddmmmyyyy D2 Daily Leq nnn n dB D3 Daily LDN nnn n dB D4 Daily CNEL nnn n dB D 5 hn HNL for hour 0 23 nnn n dB D 6 hn HNL partial hour indicator c D7 Daily Lmin nnn n dB D8 Daily Lmax nnn n dB D9 Daily Lpeak nnn n dB D10 Daily Luwpk nnn n dB Dil Daily Run Time hh mm ss mm ss ss D 12 Daily Avg Wind Speed nnn n or nnnnn unused 013 Daily Gust nnn n or nnnnn unused D14 Daily Gust Direction ccc unused DIS Daily Gust Time hh mm ss unused D16 Daily Wind Excd Count nnnnn unused D17 Daily Windy Percentage nnn unused D 18 n Daily Direction n 1 8 ccennn unused D19 Daily Ln Table in hexadecimal hhhhhh hhhhhh hhhhhh ih D 101 Daily Variables 1 4 7 11 Macro D 102 Daily HNLs 5 0 23 6 0 23 Macro D 103 Daily Wind 12 17 18 1 8 Macro unused B 28 Model 820 Technical Reference Manual Run Log Variables Brackets in the syntax indicate optional characters and oper ands Syntax Response L og var
25. 46 has a range from 0 to 255 dB Step 2 Press the v key and choose the desired dB level for the Current Threshold Larson Davis has preset this parameter to 80 dB 5 10 Taking a Measurement The appropriate value for this parameter 15 established enforcement authorities in various countries In the USA OSHA man dates a 5 dB exchange rate 3 dB is common in most other countries Note that these can be changed without a Reset all The normal Dose setting for threshold is 80 dB which allows the instrument to virtually ignore sound below that level as it does not contribute significantly to the weight of the measurement data sought and saves memory as well If you wish to change this level press Modify enter the desired dB numerically and press Enter Model 820 Technical Reference Manual The Current Criterion is the next parameter item 47 and has been preset to 90 dB in a range of 0 to 255 dB Step 3 Press key item 47 Press if you wish to keep the 90 dB level or press Modify enter the desired dB numerically and press Enter The Current Dose is often used as a second Dose measure ment The collected data is available on the printout The Overall Dose parameters have the same available settings as the current settings and are accessed in the same way Step 4 To access items 48 50 Overall Exchange Rate Overall Threshold Overall Criterion press key Full Dose Hours item 51
26. EEPROM Storing a Setup The Model 820 must be stopped and memory reset to store to the EEPROM Step 1 Press GHIFT Remember to reset memory press SHIFT 7 Enter The EEPROM register is the default In this instance the title of the measurement is TECH WRITER Model 820 Technical Reference Manual 8 5 Step 2 Step 3 The keys will scroll through the two RAM registers 0 9 For example press x twice The RAM register 1 is empty To store the current setup to the displayed RAM 1 register press Recalling Setup Memory must be reset before a recall of setup parameters can be accomplished Step 1 Step 2 8 6 In the stop mode press SHIFT Enter to reset memory Then press GHIFT 5 The EEPROM is again the default Use x to scroll through the ten RAM registers or the pro grammed ROM setups RAM registers 0 to 9 and EEPROM register will recall pre viously stored calibration data STORE saves the CAL data so that the calibration for several different microphones may be stored and recalled as desired For example Register I could store the calibra tion for a Model 2560 microphone 2 for a Model 2540 3 for dBuV Model 820 Technical Reference Manual Model 820 Setup Parameters ROM registers A B and do not affect calibration data Setup parameters of the Model 820 are
27. Leg and SEL of maximum PassBy PSBY d Leq and Max RMS level Step 3 To return to the Exceedance PassBy data screens press SHIFT 4 Overload The Single Highest Passby event is accessed by pressing SHIFT and 4 while in the EXCD Mode It should be noted that during any measurement an OVER LOAD may occur Such occurrences happen when input sig nals exceed internal circuitry limits such as dropping or jarring the instrument Should an OVERLOAD occur during a measurement the data accumulated during the occurrence will not be accurate The Model 820 registers an OVERLOAD in the upper right corner of the display where the running figure appears The figure takes one step each second At intervals 8 seconds apart the letters O V L D will appear in succession The measurement should be retaken The Interval Report on the printout will indicate which interval had the OVERLOAD Setting the Daily History Parameter The Model 820 automatically calculates daily sound statistics including Leg 24 Lay CNEL Lyeaks Lipi 5 Lax and Lmin and for each hour of the day the hourly Leg the hourly EXCD Leq and the resultant Background Leg eq Six L percentiles optional see parameter 206 7 14 Overload Model 820 Technical Reference Manual Step 1 access item 88 Daily Enable press 5 Choose Yes if you wish this SHIFT and 4 option enables Yes No Daily Noise History can only be viewed in
28. Level SEL The total sound energy in a specific time period The equation for Sound Pressure C 14 it is T Poa SEL 101080 2 Pol The sound pressure is squared and integrated over a specific period of time T5 T4 this is called the sound exposure and has the units Pascal squared seconds or Pascal squared hours PO is the refer ence pressure of 20 uPa and T is reference time of 1 second It is then put into logarithmic form It is important to note that it is not an average since the reference time is not the same as the inte gration time The physical characteristic of sound that can be detected by micro phones Not all pressure signals detected by a microphone are sound e g wind noise It is the amplitude of the oscillating sound pressure and is measured in Pascals Pa Newtons per square meter which is a metric equivalent of pounds per square inch To measure sound the oscillating pressure must be separated from the steady barometric pressure with a detector The detector takes out the steady pressure so only the oscillating pressure remains It then squares the pressure takes the time average and then takes the square root this is called rms for root mean square There are sev eral ways this can be done Model 820 Technical Reference Manual Moving Average The averaging process is continually accepting new data so it is similar to an exponential moving average The equation fo
29. Model 820 allows synchroniz ing the interval report with the Daily History Report If Yes is entered the Interval Report will be started or restarted if already run ning at the start of each hour For this to work properly the Interval Time should be one hour or some multiples of hours The benefit of synchronizing the hourly levels and the interval reports is that all the statistics Linge Ly etc are available for the hourly noise lev els that make up the daily report Yes This option allows the six L s for the interval report to be stored Yes This option will cause the Model 820 to automatically stop at the end of each interval allowing the precise timing of a series of manual measurements To start a new measurement the key must be pushed No This mode must be off for all automated measurements It is rec ommended that Intv Time Sync be Model 820 Technical Reference Manual Step 8 view Interval Histories after a measurement has been taken press 3 A screen similar to the one below will appear Step 9 Examine data available in each INTV Press gt and scroll to each The 4 will also work and the scroll is a loop set to No to get the full desired period Eight screens are available from the INTV mode The screen at the left gives the Time and Date of a given Interval Duration Leg Lmin and Ling Peak and UWPK the level setting measurements INTV a gives time
30. Not Implemented 156 System Locked 157 A D Stack Full 158 A D Over Run 159 Serial Port Framing 160 Serial Port Line Noisy 161 Serial Port Over Run 162 Wait for Stabilization 163 Power Turned 164 Time Date Not Set 165 Printer Already BUSY 166 Lithium Battery Low 167 Timer ON Pending Model 820 Technical Reference Manual B 33 Modem Control Mode The modem control mode enables the Model 820 to automati cally dial out upon an exceedance or a low memory condition This mode also enables the Model 820 to answer the phone so that instructions can be received The modem must be Hayes TM compatible and set to respond to commands using numeric codes non verboses Setup parameters 154 to 157 control this feature Modem Mode 154 If the Modem Mode is Yes the Model 820 will dial the Phone on the events selected by the Dial Out Mode defined below Dial Out Mode 155 None The Model 820 will not dial a computer for any rea son Excd The Model 820 will dial a computer to report when an illegal exceedance is logged into memory An illegal exceedance is when Excd Lmax gt RMS Excd Level 2 parameter 62 The phone will also be dialed if the mem ory is low e Phone The valid characters are those recog nized by the modem to which the Model 820 is attached and generally include W will wait for another dial ton
31. Peak UWPK or Max RMS level Lmax with each RMS history sam ple Step 6 You may press and make your selection with gt and then press Enter Step 7 Press the v to item 83 Hist Period See the following step 0 255 units Step 8 Press v to item 84 Hist Period Units These options select the history period length as determined by the 1 32s 1 0s 10 0s 60 0s value set in parameter 83 times the units set in parameter 84 For example selecting a period of 180 and a unit of 10 seconds would 7 2 Setting and Viewing Advanced Functions Model 820 Technical Reference Manual Step9 Use the and 0 to select the value you want for this field Step 10 Press v to item 85 Hist Base The setting range is 0 255 dB Step 11 To enter a value press Modify the value Enter Step 12 Press the v to item 86 Hist Base Mode Off RMS Peak Step 13 To change the field press 0 and Enter Step 14 Press v to item 87 Histogram Resolution for these options 1 8 1 2 1 0 2 0 5 0 10 Step 15 Select the value you want Press to the proper setting and then press Enter Time History Data Chapter 5 explained how to perform a measurement To exam ine the Time History of that measurement take the following steps Model 820 Technical Reference Manual give 1800 seconds or 30 minutes for each Leq history period A period of 2 and a unit of 1 32 sec ond would result in a history sto
32. RR RU To A 12 Dimensions Weight with Microphone Preamplifier and Battery A 12 Appendix B Serial Port Interface Remote Control B 1 Model INT002 Interface B 2 Daisy Chain Addressing enient aa E E e n B 2 Commands ensani E E E P R B 3 History Oriented Commands Mode Commands eini renr B 4 Read ite ei a Eee O Roe B 5 Other Read B 11 Group Read Programming eee ee ed eae ee he B 11 Setting Parameters ee tesoro the ere DER Rb B 12 Numeric Parameters eee ete e e e ree e ede B 12 Indexed Parameters etate eet RIS eiie B 13 Character String Parameters essere B 14 Template Parameters nte te UR Id tate es B 14 Query Parameters x ei dee Pee enis B 15 Histogram Reports 19 Tailored Report une tete ed aa e ets B 19 Miscellaneous eere B 20 Error Checking iO B 22 History Records actore B 24 Types of History see esee e eee ad ih e YER e B 24 sss esf t Rp rem pe B 24 Backup ene E EN Une co B 25 eh d eh 25 History Data 25 Exceedance History 25 Interval History B 26 Daily His
33. as a count of all of the History Records stored in memory HIST HIST The Time History function is a record of short interval L reading and optionally a Peak UWPK or Lmax reading The interval can vary from 1 second to 255 minutes His tory period is set by parameters 83 84 LOG The Run Stop Log is a time record of all the actions which start or stop the data tak ing process of the Model 820 2 4 Understanding the Model 820 Keypad Model 820 Technical Reference Manual Keys Functions CAL SLM CAL Calibration information and control Initially in the CAL a display the current calibration offset is displayed with a flashing prompt to press either key to check the calibration or press key to change calibration SLM The Sound Level Meter function dis plays the current Sound Pressure Level SPL while the instrument is in the Run Mode or the SPL at the instant it was last stopped LMAX Lmax The maximum SPL or Lmax 15 the largest sampled SPL for the overall measure ment period displayed with the date and time of its occurrence Two additional screens accessed by pressing the left or right arrows show the number of times the SPL exceeded two fixed levels Luv The minimum SPL or Lj is the low est sampled SPL for the overall measurement UWPK PEAK PEAK The highest weighted Peak Detector output level Lpk Date and time of the occur rence of the Lp
34. basic function of the Model 820 is to measure sound pressure Follow these steps to examine the SLM function key SLM Step 1 Turn the Model 820 on and wait for the unit to become stable Press The stick figure in the Model 820 Technical Reference ManualPerforming a Measurement Reading the Data 5 1 upper right corner will appear to be running This instrument can store a great variety of measurements in mem ory depending on the current parameter setup Nevertheless current measurements are always easily available from the keypad Step 2 With the instrument in RUN mode press The The display now reads a C current sound pressure level is displayed weighted slow average reading of 84 5 dBC re 20 The level 15 also shown on a semi analog bar graph Parameters 39 43 affect these values and parameters 45 47 effect the Current SLM Step 3 An additional six screens are available from this dis The Lmin and Lmax for the current play Press the key to access the first reading at the current time are dis played in the first screen Notice that the current sound pressure level continues to read in the upper left corner and fluctuates Note that even in the stop mode the Model 820 continues to monitor a Parameter 61 RMS Exceedance SPL while in this window b Parameter 62 RMS Exceedance 2 The space beneath 88 4 in this screen where the are c Parameter 63
35. be removed in normal use Rain droplets or other foreign matter on the diaphragm may alter the microphones 5 Model 820 Technical Reference Manual 20 key membrane keypad Model 820 precision hand held Sound Level Meter with integral nose cone Powered internally by 9 volt cell or by an external battery or AC DC adapter e WS0013 1 2 inch windscreen An AC DC mini phone connector with pinout shown on page 4 8 A 5 pin cable connector with the pinout shown in figure Figure 1 2 Note that this connector is used to access external power 2 TXD Transmitted Data fm 820 3 Received Data to 820 4 External Battery to 820 5 DTR Data Terminal Ready 1 Ground Figure 1 2 External 5 pin Cable Connector Pinout response Please use a windscreen whenever possible Using cable CBL038 or INTO02 and related software the 5 pin connector is used both for external power and for the remote interface Model 820 Technical Reference Manual Model 820 Components 1 9 Block Diagram All the standard functions of a precision sound level meter are provided instantaneous level Li SEL Li dose projected dose etc In addition many valuable parameters can be stored time history interval data such as L s and Leg exceedance and exceedance time history etc Level calibration is performed in a few key strokes and every change or check is entered in a calibration log The Mod
36. close source can be louder than that of a more distant but stronger source Therefore measurements made here can be used to separate the various sources of sound but are not useful in predicting the sound levels and sound spectrum far from the source Typically it is unwanted sound This word adds the response of humans to the physical phenomenon of sound The descriptor should be used only when negative effects on people are known to Model 820 Technical Reference Manual 11 Noise Dose D Noise Exposure OSHA Level Losna occur Unfortunately this word is used also to describe sounds with no tonal content random Ambient The all encompassing sound at a given location caused by all sources of sound It is generally random but need not be Background The all encompassing sound at a given location caused by all sources of sound but excluding the source to be mea sured It is essentially the sound that interferes with a measure ment Pink It is a random sound that maintains constant energy per octave Pink light is similar to pink noise in that it has a higher level at the lower frequencies red end of the spectrum White It is a random sound that contains equal energy at each fre quency In this respect it is similar to white light It is the percentage of time a person is exposed to noise that is potentially damaging to hearing Zero represents no exposure and 100 or more represents complete exposure It is calc
37. discriminate against higher frequencies High Pass A frequency filter that permits signals to pass through that have frequencies above a certain fixed frequency called a cut off frequency It is used to discriminate against lower frequencies Bandpass A frequency filter that permits signals to pass through that have frequencies above a certain fixed frequency called a lower cutoff frequency and below a certain fixed frequency called an upper cutoff frequency The difference between the two cutoff frequencies is called the bandwidth It is used to discriminate against both lower and higher frequencies so it passes only a band of frequencies Octave band A bandpass frequency filter that permits signals to pass through that have a bandwidth based on octaves An octave 1s a doubling of frequency so the upper cutoff frequency is twice the lower cutoff frequency This filter is often further subdivided in 1 3 and 1 12 octaves 3 and 12 bands per octave for finer frequency resolution Instruments with these filters have a sufficient number of them to cover the usual range of frequencies encountered in sound and vibration measurements The frequency chosen to describe the band is that of the center frequency Note table in Fre quency Filter Frequency Weighting A special frequency filter that adjusts the amplitude of all parts of the frequency spectrum of the sound or vibration unlike band pass filters It can be composed of one or more of t
38. followed by 4 The Timer parameters 21 27 SHIFT and The following display will begin with this screen parameter appear 21 Model 820 Technical Reference Manual Timed Measurement 6 1 Step 2 Press to access the cursor in brackets With Block Run Time I on Run Date to the brackets flashing use gt to select one of four Stop Time I on Stop Date possibilities I Day Run Time 1 to Stop Time 1 each day from Run Date to Stop Off Block 1 Day or 2 Day Date 2 Day Run Time 1 to Stop Timel and Run Time 2 to Stop Time 2 each day from Run Date to Stop Date Example Suppose we want to measure a given area near a large machine in a factory for 5 days 2 periods each day Step 3 To do this choose 2 Day and press Enter Step 4 To continue press the v to access the next parame ter screen To continue our example we want to start 26 September at 8 30 A M and end at 12 00 noon begin again at 1 00 P M and end at 4 30 P M each day for 5 days Step 5 Press to change the date and enter 0 9 If the date is incorrect simply 26 0 6 Press Enter The new Timer Run Date press and enter the correct is now 26 Sep 1996 data then press Enter 6 2 Using the Timer for Unattended Readings Model 820 Technical Reference Manual Step 6 Step 7 Step 8 Step 9 To access Timer Stop press the v A Previously entered date will appear To change the date press and ente
39. for your study 168 Rt EXCD Report No Yes Print exceedance report in real time 169 Rt INTV Report No Yes Print interval report in real time 170 Rt HIST Report No Yes Print history report in real time 171 Rt RUN LOG No Yes Print run log history 172 Rt Daily Report No Yes Print daily report 173 Rt CAL Report No Yes Print cal report 10 4 Real time Printing Model 820 Technical Reference Manual These reports are automatically printed when you push 7 As the data is collected it is printed out according to those parameters settings in the Time History 80 87 Interval His tory 72 79 and the Exceedance History 61 65 For instance if the history period parameter 83 is set to 6 seconds the printer will print a bar graph every 6 seconds This will continue until you push again These parameters are only available by pressing and entering the parameter numbers directly Model 820 Technical Reference Manual Real time Printing 10 5 APPENDIX Specifications This Appendix contains the specifications for the Model 820 in the following order Reference Direction Measurement Ranges Reference Level Frequency Weighting Detector Time Weightings Effects of Temperature Effects of Humidity Limits of Temperature and Humidity Microphone Extension Cables Positioning of Instrument and Observer for Best Measure ments e AC and
40. generally set to be the low est value of the quantity Department of Defense Level Lpop The Average Sound Level calculated in accordance with Dose Detector Department of Defense Exchange Rate and Threshold Level See Average Sound Level See Noise Dose The part of a sound level meter that converts the actual fluctuating sound or vibration signal from the microphone to one that indicates its amplitude It first squares the signal then averages it in accor dance with the time weighting characteristic and then takes the square root This results in an amplitude described as rms root mean square Eight Hour Time Weighted Average Sound Level L 8 It is the constant sound level that would expose a person to the same Noise Dose as the actual unsteady sound levels The equation for it is D Lywa g L qLogy 0 NOTE This definition applies only for a Criterion Duration of 8 hours Standard ANSI 612 19 Energy Equivalent Sound Level Leq The level of a constant sound over a specific time period that has the same sound energy as the actual unsteady sound over the same period 1 Leg 1010210 EC ONES per where p is the sound pressure and the Measurement Duration spe cific time period See Sound Exposure Level Model 820 Technical Reference Manual C5 Exchange Rate Q Exchange Rate Factor q Exposure Factor k It is defined in ANSI S1 25 as Far Field Free Fiel
41. has a range of 0 to 99 hours but is normally set to an 8 hour workday Step 5 To access Full Dose Hours press key Parameters 52 54 are a second set used to calculate overall dose from the overall data Data already in memory is recalcu lated with new parameters using LDL log Data Logic Step 6 look at DOSE press 525 Step 7 look at Projected Dose press M to the PROJ b screen Step 8 Ifyou wish to alter the LDL Exchange Threshold or Criterion settings press enter the desired val ues and press Enter Step 9 look at LDL press GHIFT and 225 Model 820 Technical Reference Manual Damage to hearing normally occurs with lengthy exposure to sound at 90 dB and above For this reason the Criterion is generally set at 90 dB Changes can be made in any dis play by pressing Modify entering desired values and pressing Enter The overall criterion level set in item 50 and the dose hours set in item 51 determine what is 10095 dose OSHA criterion is 90 dB Thresh old is 80 dB Exchange Rate is 5 dB and the Full Dose hours Cri terion Time is 8 dB This step will not work while in the SETUP mode This step will not work while in the SETUP mode either Taking a Measurement 5 11 Dose readings are usually read and have more meaning after the measurement is completed Returning to our recent mea surement let s examine the DOSE key and look at the values recorded
42. in the far field the sources have all merged into one so that measurements made even further away will be no different See the definition of Geometric Near Field for the advantages of being in the geometric far field A sound field that is free of reflections This does not mean that the sound is all coming from one direction as is often assumed since the source of sound may be spatially extensive See the definitions of near and far fields for more detail This definition is often used in conjunction with reverberant field The rate at which an oscillating signal completes a complete cycle by returning to the original value It can be expressed in cycles per second and the value has the unit symbol Hz Hertz added and the Model 820 Technical Reference Manual Frequency Band Pass Filter Frequency Filter Weighted letter f is used for a universal descriptor It can also be expressed in radians per second which has no symbol and the greek letter is used for a universal descriptor The two expressions are related through the expression 2 4f The part of certain sound level meters that divides the frequency spectrum on the sound or vibration into a part that is unchanged and a part that is filtered out It can be composed of one or more of the following types Low Pass A frequency filter that permits signals to pass through that have frequencies below a certain fixed frequency called a cut off frequency It 1s used to
43. key second from the lower left The cursor will auto matically move to the next letter Enter the A key Enter the R S O keys consecu tively or one at a time Complete the rest of the entries in the same fashion Three lines are available for entry i e company address telephone The first fourth lines appear on screen when the 820 is turned on Model 820 Technical Reference Step 10 To exit the setup mode press Setting Time Date and Day parameters Once you have set the parameters you can now enter the cor rect time and date The Model 820 has a 24 hour military time clock where afternoon hours are denoted by adding 12 hours e g 3 45 p m 15 45 hrs Modify this parameter as fol lows Step 1 With the Model 820 on press SHIFT 155 The current time is displayed If it is incorrect enter the correct time Step 2 Press the key and use the numeric keys to enter correct time and then press Enter Step 3 The Current Date is the next field Press v to The current date will appear If it the next display is incorrect press to access the field enter the correct date using the corresponding number keys and press Enter Step 4 Day of the Week is in the next field Press v to Jf the day is incorrect press access that field and gt or to the correct day Press Enter Model 820 Technical Reference Manual Setting Time Date and Day par
44. labo ratory use Part 1 General Requirements Power Supply Internal 9 V battery typically 20 hour operation actual run times vary depending on operating conditions External 7 to 16 VDC 30 mA current drain e Battery life indication selected from keyboard or computer program Dimensions Weight with Microphone Preamplifier and Battery Width 3in 7 6 cm Length 13 in 33 cm Depth 1 0 in 2 5 cm Weight 13 oz 370 gm Weight w o preamp amp microphone 11 oz 310 gm Shipping weight 3 16 1 4 kg A 12 Power Supply Model 820 Technical Reference Manual APPENDIX Serial Port Interface Remote Control The Model 820 is fully controllable remotely via Serial Port interface Setup items and operational mode can be altered Data can also be dumped to or queried by the controlling com puter The Model 820 may be connected to the computer directly or through a modem A network of many instruments can be formed all controlled by one computer by using the address ability mode This chapter will describe the Serial Port interfacing of the Model 820 and the various interface commands with their syn tax Modem control is also covered These commands are a subset of the Larson Davis Model 870 commands In this chapter we will cover the following items e Model INT002 Interface 2 Daisy Chain Addressing sese 3 Commands coe cape to eR FRE E
45. level The table below shows the actual value of a specific item such as sound pressure for which the level is to be determined First the value is put into exponential form in powers of ten the exponent is the Bel The exponent is then multiplied by ten to yield the decibel This procedure converts multiplication into addition every time 10 is added to the level the value is tiplied by 10 When the value is not a even multiple of ten the exponent is more complicated as shown in the table Every time the level increases by 3 dB the value is multiplied by 2 doubled These two rules are worth remembering Linear form Level form Exponential Form of 10 Exponent Ration of Value to Reference Ratio 1 10 0 10 10 10 100 10 20 200 10 23 1000 10 30 10000 10 40 100000 10 50 1000000 10 60 The definition of decibel is intended for power like quantities W Sometimes power is represented by the square of a measured quan tity and this results in a different form of the equation See Sound Pressure Level The value of the item in the table is not the value of the quantity itself but the ratio of that quantity to a reference quantity So for Model 820 Technical Reference Manual L w Wo 0 every level in decibels there must be a reference quantity When the quantity equals the reference quantity the level is zero To keep the values above zero the reference is
46. listed below Modify ing some setup parameters such as going from a FAST to a SLOW meter response may not be allowed unless the data is reset This prevents corruption of the overall noise data Parameters are listed below in logical groups with their num ber and direct index key if available Valid entry formats are listed 0 for numerical 0 for selection Some reserved parameters or selections are not available Many of these are active in the Model 870 the Model 820 s big brother System 1 20 GR Gm amp The following parameters define measurement names and determine interface parameters 1 No Prompt Reset ALL Data Entry No Yes Comment This parameter allows a SHIFT RESET without leaving SETUP Note If this parameter is set to Yes a RESET will occur and the parameter will automatically revert to No 2 4 Name up to 30 characters Place any message you desire in these 3 lines The 3 lines of name are sav able only in EEPROM Title up to 30 characters Used to describe a measurement or setup Current Time hh mm ss also accessed w SHIFT Model 820 Technical Reference Manual 8 7 Current Date mm dd yy Leap years are considered For years less than the year manufactured the 21st century is assumed 2000 2092 otherwise the 20th century is used 1993 1999 Day of Week Sun Sat Baud Rate
47. nolog var Example L1 Run Stop number Ll Run Stop Number nnnnn L2 Run Stop Type RUN STOP CONT PAUSE MARK L3 Cause TIMER KEY A D n HALT INTV BATT L4 Day Date and Time ddd ddmmmyyyy hh mm ss L101 Run Log Variables L1 L4 all variable values Calibration History Variables Brackets in the syntax indicate optional characters Syntax Response C alibration var_no cal_var Example Cl checked level CI Checked Level nnn n C2 Day Date and Time ddd ddmmmyyyy hh mm ss Calibration Mode Manual Auto C4 Cal Status OK Bad C101 Cal Variables 1 4 all variable values Time History Variables Brackets in the syntax indicate optional characters and oper ands Syntax Response Model 820 Technical Reference Manual B 29 H istory var no time var Example H2 Peak level in current record H1 RMS Level nnn n dB H2 Peak Level nnn n dB H3 Run Time of Sample calc hhhhh mm hh mm ss mm ss ss H4 HISTORY BARGRAPH Histogram Table Variables Brackets ands Table in the syntax indicate optional characters and oper 1 RMS 2 Peak e 3 Unweighted Peak Default is last used table or RMS Syntax Response T able var_no table table_var Example RMS current bin leve
48. rms and weighted peak detectors Analog to digital conversion is performed maintaining a full 110 dB range for the RMS signal The numeric data is then analyzed by the Model 820 s dedicated digital processor With system programming residing in PROMs programmable read only memory upgrades or future changes in regulations can easily be accommodated Measurement modes selected and shown in informative screens on the 32 character liquid crystal diode LCD display The custom keypad provides direct access to the needed data or setup item An accurate built in Quartz clock calendar and timer are ideal for unattended measurements and time stamping of events The 256 kB memory can be used to store time exceedance or interval data as selected by the user All can be printed or transferred to an external computer via the serial port even during data gathering Larson Davis PC compatible software employs a binary data dump method for even faster data transfer External battery or DC power may be supplied through the same five pin connector Getting Started This section outlines the steps you need to follow when you first receive and unpack the Model 820 The following topics are covered Unpacking and Inspection Accessories and Optional Equipment Connecting Internal or External Power Environmental Considerations Model 820 Technical Reference Manual Getting Started Preparing to use the Model 820 Connecting t
49. setting the time and date The Model 820 will turn itself on and begin measurement at the appropriate time Using the Time Key Functions In Chapter 5 we learned to take a measurement and examine some of the data gathered during that reading The TIME key functions as a record of when the last measurement started 6 4 Using the Time Key Functions Model 820 Technical Reference Manual Two screens are available in this function Step 1 Press SHIFT and to access this information Current time day and day of week are controlled by parameter 6 8 This screen displays the time and date the current or last measure ment began Step 2 Press the key to access the second screen The second display shows the cur rent date day and time Step 3 Press to return to the main screen Setting the Password Lock to Protect Settings The Model 820 SLM can insure that your settings will not be disturbed by providing a Lock Password parameter items 28 34 Step 1 From the previous field press v or from the main screen press Modify 2 8 Enter You can also press te SHIFT 5 amp 5 Step 2 Press Modify and enter your personal combination of Refer to Chapter 4 to review enter numbers or letters from 1 8 characters ing numbers or letters by using the SHIFT key Model 820 Technical Reference Manual Setting the Password Lock to Protect Settings 6 5 Step 3 Step 4
50. ss s R6 _O STIME OverAll Start Date and Time ddmmmyy hh mm ss R7 _C RTIME Current Runtime hhhhh mm ss s R8 _C STIME Current Start Date and Time ddmmmyy hh mm ss R9 _O TWA Overall TWA Time Wght Avg nnn n dB R10 _ Overall Exchange Rate Text _C TWA Current TWA Time Wght Avg nnn n dB R12 _C XR Current Exchange Rate Text R13 _O SEL Overall SEL nnn n dB R14 _C SEL Current SEL nnn n dB R15 _O LMIN OverAll Minimum Level nnn n dB R16 _O TMIN OverAll Lmin Date and Time ddmmmyy hh mm ss R17 _C LMIN Current Minimum Level nnn n dB R18 _C TMIN Current Lmin Date and Time ddmmmyy hh mm ss R19 _O LMAX OverAll Maximum Level nnn n dB R20 _O TMAX OverAll Lmax Date and Time ddmmmyy hh mm ss R21 _C LMAX Current Maximum Level nnn n dB R22 _C TMAX Current Lmax Date and Time ddmmmyy hh mm ss R23 _O LPEAK OverAll Peak Level nnn n dB R24 _O TPEAK OverAll Lpeak Date and Time ddmmmyy hh mm ss R25 _C LPEAK Current Peak Level nnn n dB R26 _C TPEAK Current Lpeak Date and Time ddmmmyy hh mm ss R27 _O LUWPK OverAll UWPk Level nnn n dB R28 _O TUWPK OverAll Luwpk Date and Time ddmmmyy hh mm ss R29 C LUWPK Current UWPk Level nnn n dB R30 _C TUWPK Current Luwpk Date and Time ddmmmyy hh mm ss R31 RMSCNT OverAll RMS Exceedances 1 nnnnn R32 RMSCNT2 OverAll RMS Exceedances 2 nnnnn R33 _ OverAll Peak Exceedances nnnnn R34 UWPKCNT OverAll UWPk Exceedances nnnnn R35 _OVLDCNT Overloads nnnnn B 6
51. the Model 820 Keypad The keypad for the Model 820 has 20 keys as seen in the fol lowing figure Figure 2 1 Model 820 Technical Reference Manual Overview to Model 820 2 1 LARSON DAVIS 820 SLM Modify Sos 53 ES 53 ES E ey E ey Lock MEM LOG SHIFT INTV HIST Enter STR RCL RESET PRINT SETUP R S 1 INTEGRATING SOUND LEVEL METER Figure 2 1 Model 820 Keypad 2 2 Understanding the Model 820 Keypad Model 820 Technical Reference Manual These keys perform the following functions This information is covered in more detail in chapter 4 of this manual Keys Functions White White functions are accessed by pushing but tons directly Orange Orange functions are accessed by first press ing the key The smaller letters numbers above the keys are accessed by the adjoining key at the appropriate time to be explained later OFF ON Turns on the Model 820 ON Cancel When the Model 820 is on this but ton serves to return to a previous menu or Cancel the present function OFF SHIFT OFF turns off the Model 820 after it has been stopped PRINT Access to a list of reports scrolled PRINT through the display a key name is indicated for each one If there is a following the key name then the options function will be invoked after selecting that key otherwise the particular report will be printed immediately STR A permanent storage reg
52. to another One may also use a function key or directly index to the appropriate parameters Step 1 From the Setup menu press v to move down the All items in the list of parameters list of parameters one at a time can be accessed by using the and v Step 2 When the arrow keys are used in conjunction with the Shift key SHIFT the Model 820 will take you to the top or bottom of the parameters list Step 3 PressGHIFT Y to move to the bottom of the parameter list Step 4 Press the key The Model 820 moves you to the rms detector parameters Step 5 Press the GHIFT keysandthen 6 1 You are now at the beginning of the Press Exceedance parameters item 61 8 2 Model 820 Technical Reference Manual NOTE Numbers are entered at the current cursor position Enter leading zeros if necessary Changing Parameters Enter Modify Parameters may consist of numerical values character fields or selected choices Numerical or character fields are shown between parentheses Another parameter type is the template entry parameter These prompt for specific data entry For example For both types follow these simple steps Step 1 Press Modify Step 2 Enter a value from the numerical keypad Use the SHIFT key for alphabetical input Model 820 Technical Reference Manual This one has rounded brackets that mean this is an entry parameter Type the number or character desired
53. variable number time hist num variable value I nterval variable number relative rec variable value D aily variable number num variable value L og variable number relative recO variable value C alibration variable number variable value H istory variable number relative_rec variable value T ables variable number table variable value A dvance range history number acknowledge B ackup range history number acknowledge F ind record number history number acknowledge P rint report number acknowledge Mode Commands Format for the Mode Commands is Command Description MI Power On clear error message list and reset display functions to windows M2 Power Off M3 Run M4 Stop B 4 Model 820 Technical Reference Manual M5 View M6 Mark M7 Reset Current Data use S1 1 for Reset All M8 Reset Histories Only M9 High Resolution Levels to I O channel only Increased resolution I O is possible by using the M9 1 command sound levels are then sent with an additional fractional character nnn nn giving 1 100th dB resolution The Model 820 acquires noise data with 1 32 dB resolution Greater resolution is achieved through averaging HOWEVER THIS DOES NOT IMPROVE ACCURACY Refer to the specifications or device specific performance results for the accuracy of the system M 10 Lock 820 leave 820 s power on Lock 820 and P
54. yes automatically stops instrument at the end of each interval for precise timing of series of manual measure ments Use R S key to restart Time History 80 87 This third type of history is the most conventional The rms integrated level and if selected a maximum reading are stored in memory at the end of each time history period No Prompt Entry Comment 80 HIST Enable No Yes Time history report will be stored if Yes is entered Despite the Model 820 s large memory ensure antici pated requirements do not exceed available memory 81 Hist Resolution 0 1dB 1 0dB Normally all data is taken with 0 1 dB resolution 2bytes level Allows stor age of history with 1 dB resolution to conserve memory 1byte level 8 16 Model 820 Technical Reference Manual 82 Hist Save Peak No Peak UWPk Lmax This option allows saving the history period s highest weighted Peak unweighted Peak UWPk or rms level Lmax With each RMS history sample 83 Hist Period 1 255 units Multiplier of units of time in parame ter 84 sets rate at which history sam ples are stored Ex x 60 0s for minute by minute history 16 x 1 32s for 0 5 second history 84 Hist Per Units 1 32s 1 0s 10 0s 60 0s Note The rms detector is sampled 32 times s These samples are averaged into an integrated sound level Leq stored every time history period 85 His
55. 0 1 2500 0 0 12 5 6 2 200 0 1 3150 0 0 16 4 7 250 0 1 4000 0 0 20 3 5 315 0 0 5000 0 0 25 2 5 400 0 0 6300 0 0 31 5 1 7 500 0 0 8000 0 1 40 1 2 630 0 0 10000 0 1 50 0 9 800 0 0 12500 0 2 63 0 6 1000 0 0 16000 0 3 80 0 3 1250 0 0 20000 0 5 100 0 3 1600 0 0 Model 820 Technical Reference Manual Frequency Weightings A 5 AC Output FLAT Frequency Response 125 0 2 2000 0 0 6 Frequency Weightings Model 820 Technical Reference Manual Detector Time Weightings The available RMS detector time weightings are FAST SLOW and IMPULSE There are also two available PEAK detectors Weighted Peak Unweighted Peak Weighted Peak Detector Rise Time 60 Unweighted Peak Detector Rise Time 30 us Effects of Temperature The SPL level varies 6 0 5 dB when the complete instrument is tested over the 10 C to 50 C temperature range The refer ence reading for this test is taken at 20 C and 36 relative humidity RH the input signal is at 1000 Hz Effects of Humidly The SPL level varies 6 0 5 dB when the complete instrument is tested over the 30 to 90 RH range This test is performed at 40 C with an input signal of 1000 Hz Limits of Temperature and Humidity Permanent damage can occur when stored or operated above 60 C or below 20 C Condensation of moisture will make readings inaccurate but will be correct when moisture has dis sipated Microphone Extension Cables When measuring signals below
56. 12 Time allowed Exposure time Ti 1 E 2 6 18 Time History o deoa edente 8 15 data RR ert 7 3 Time History see History 2 4 Time Weighted Average see T A 2 7 Index Timed Measurement Chapter 6 etit tnus 6 1 Timer for unattended readings 6 1 internal eene 5 4 2 6 parameters 8 10 JH Ign de PEE 2 9 Turning Off directions for 2 11 TWA time weighted average sound level TWA LTWA TC C 17 Type 2 1 Model 820 1 1 1 5 T A 2 7 U Unweighted Peak 2 5 UIDI e MEAT hr 5 5 5 7 V Variables calibration history B 29 daily history B 28 exceedance history B 25 histogram B 30 histogram table B 30 interval eere B 26 interval history B 26 run eG B 29 time history eese B 29 Vibration RUE ND C 18 W Warnings error messages B 32 Wavelength l GIOSSANY 18 Wavenumber glossa C 18 Weighted 8 hour time weighted average sound 5 Weighting
57. 13 The commands may be spelled out though only the first character is significant i e READ 123 may be abbreviated to R123 Every command has a response to acknowledge that it was received correctly and to provide data requested For high reliability systems there is an error checking protocol that is added to ensure proper command data transferal See Error Checking Protocol on page 34 The following tables summarize all of the commands and are listed in this order mode control commands first parameter commands next data extraction command and report data download command last Square brackets indicate optional characters or operands Syntax Response R ead variable number 0 operand_2 variable value S et parameter number parameter value acknowledge S et parameter number fixed parameter index acknowledge S et parameter number fixed parameter prompt acknowledge i e Set 8 Thu will set day of week to Thursday Q uery parameter number 0 option flags parameter value Model 820 Technical Reference Manual Option flags may be added for combined effect 32 Index Number 8 Tab over response 2 print in braces 1 Print parameter name K ey key_simulation_string acknowledge M ode mode number acknowledge History Oriented Commands E xceedance variable number relative 0 variable value E xceedance
58. 6 0 0 1600 1 0 0 0 1 2000 2000 1 2 0 1 0 2 2500 13 0 2 0 3 3150 1 2 0 4 0 5 4000 4000 1 0 0 7 0 8 5000 0 5 1 2 1 3 6300 0 1 1 9 2 0 8000 8000 1 1 2 9 3 0 10000 2 5 4 3 4 4 12500 4 3 6 1 6 2 16000 16000 6 6 8 4 8 5 20000 9 3 11 1 11 2 See Energy Equivalent Sound Level Sound Level Energy Average and Time Weighted Average A descriptor of a measured physical quantity typically used in sound and vibration measurements It is attached to the name of the physical quantity to denote that it is a logarithmic measure of the quantity and not the quantity itself The word decibel is often Model 820 Technical Reference Manual Measurement Duration T Microphone Guidelines added after the number to express the same thing When frequency weighting is used the annotation is often expressed as dB A or dB B The time period of measurement It applies to hearing damage risk and is generally expressed in hours Standard ANSI 512 19 Microphone Types A device for detecting the presence of sound Most often it converts the changing pressure associated with sound into an electrical voltage that duplicates the changes It can be composed of one of the following types Capacitor Condenser A microphone that uses the motion of a thin diaphragm caused by the sound to change the capacitance of an electrical circuit and thereby to create a signal For high sensi tivity
59. AL TIME HIST REPORT x 171 Q RTLOG REAL TIME RUN LOG RPT x Q172 Q RTDAY REAL TIME DAILY REPORT x 173 Q RTCAL REAL TIME CAL REPORT x Q174 Q RTFRMT UNFORMATTED REPORTS x Q175 Q RPTBEG Begin Printing x Q 176 Q PTYPE PRINTER TYPE x 177 Q RPT DATA REPORT x Q178 Q RPT R S AND CAL LOG x Q179 Q RPT SETUP REPORT x Q 180 Q RPT RMS HISTOGRAM TABLE x 181 Q RMSLO RMS HISTOGRAM TABLE LOW VALUE n B 20 Model 820 Technical Reference Manual Q 182 Q RMSHI RMS HISTOGRAM TABLE HI VALUE n Q 183 Q RMSRS RMS HISTOGRAM TABLE RESOLUTION x Q 184 Q RPT PEAK HISTOGRAM TABLE x Q 185 Q RPT PEAK HISTOGRAM TABLE LOW VALUE n Q 186 Q RPT PEAK HISTOGRAM TABLE HI VALUE n Q 187 Q RPT PEAK HISTOGRAM TABLE RESOL x Q 188 Q RPT UWPK HISTOGRAM TABLE x Q 189 Q RPT UWPK HISTOGRAM TABLE LOW VALUE n Q 190 Q RPT UWPK HISTOGRAM TABLE HI VALUE n Q191 Q RPT UWPK HISTOGRAM TABLE RESOL x Q 192 Q RPT EXCD REPORT x Q 193 Q RPT EXCD REPORT LOW RECORD n Q 194 Q RPT EXCD REPORT HIGH RECORD n Q 195 Q RPT INTV REPORT x Q 196 Q RPT INTV REPORT LOW RECORD n Q 197 Q RPT INTV REPORT HIGH RECORD n Q 198 Q RPT HIST REPORT x Q 199 Q RPT HIST REPORT LOW RECORD n Q 200 Q RPT HIST REPORT HIGH RECORD n 201 Q RPTEND DAILY NOISE REPORT x Q 202 Q CALMODE CALIBRATION MODE Q 203 Q ULCO
60. DC Outputs Reference Frequency Stabilization Time Microphone Electrical Impedance Functions Measured Data Storage Model 820 Technical Reference Manual Specifications 1 Data Communications Digital Display Digital Display Resolution Display Bargraph Real time Clock Calendar Run time Clock Typical Noise Floors Standards Met Power Supply Dimensions Weight with Microphone Preamplifier and Battery Type The Larson Davis Model 820 with attached PRM 828 preamp and Model 2541 microphone is a combination Type 1 preci sion integrating sound level meter and statistical data logger The Model 820 can also be used with any of the Larson Davis 1 2 condenser microphones They may also be used with any Larson Davis 1 4 or 1 microphones provided they are used with an ADPO11 1 4 to 1 2 preamp adapter or an ADPO08 1 to1 2 preamp adapter attached to the PRM 828 The Model 820 polarization voltage can be set to either 200V or 28V Reference Direction The reference direction 1s perpendicular to the plane of the microphone diaphragm when using a free field microphone e g 2540 or 2541 in a free field The microphone should be pointed directly at the source When using a random incident microphone in a free field the A 2 Type Model 820 Technical Reference Manual microphone should be pointed 80 degrees off axis of the source of the sound When in a random sound field a random incide
61. E 8 8 Baud Bale setae edd 8 8 Dc sets 1 10 output specifications A 8 Block diagram Decibel C4 Model 820 1 10 Department of Defense level secet tee enr C 5 Detectors onde eres 8 12 Calendar C 5 A 10 Diagram 1 6 7 10 1 passby cedi 7 13 glossary C 2 Dial Out Mode B 34 Key os dto 2 5 Dialing Procedure B 35 Model o 1 2 Character Parameters Index d 2 7 projected 5 13 DSP80 Components 1 7 Duration 9 Dynamic range 1 5 E EEPROM sor e dS 8 6 8 5 Enter changing parameters 8 3 Cyr 2 4 1 18 effects of Temperature A 7 Equivalent Level See Leq 2 6 32 messages and warnings 8 4 B 32 Error Checking jon B 22 Exceedance 8 14 n i ea 7 10 CEEE 2 4 parameters
62. E 3 Group Read Programming adl Setting Parameters entente 12 e Query 15 History Records 23 History Data 25 gt Print C tnmarids eoe Rene 30 Error Messages and 2 31 Modem Control 36 Model 820 Technical Reference Manual Serial Port Interface Remote Control B 1 Model INT002 Interface Cable The Serial Port communication is made through the 5 pin con nector at the base of the Model 820 Interface interface signals usually need to be converted for proper communication with desktop computers The Model INT002 Cable level converter is required for this purpose Its electronic circuits provide the correct signal levels and polarities When used with the AC DC adapter the INT002 also powers the units externally min imizing battery depletion which can be substantial during Serial Port transfers Step 1 With the instrument turned off insert the cable con nector in the 5 pin port Step 2 Connect the cable to the of the computer using the supplied 9 25 pin adapter if necessary Signal 5 Pin configurations for the INT002 follow 820 5 pin Connector End Computer DB 9 Connector End Pinl Shield Pin5 Shield Pin 2 Red Pin 3 Red Pin3 Yellow Pin 2 Yellow Pin4 Blue Pin 5 White Pin 4 Blue Pin 6 White Pin 8 White Daisy Chain Addressing A network of instruments may be interconnected to one com puter using
63. IME SYNC Q77 Q IVLN NTV SAVE Ln S Q78 Q IVADEN NTV SAVE A D unused Q 79 Q IVSTOP INTV AUTO STOP Q 80 Q HSTENB ENABLE TIME HIST 081 Q HSTRES HIST RESOLUTION 082 Q HSTPK HIST SAVE PEAK 083 Q HSTPER HIST PERIOD 084 Q HSTUNIT HIST PERIOD UNITS Q 85 Q HSTBASE HIST BASE Q 86 Q HSTMODE HIST BASE MODE Q87 Q HGRES HISTOGRAM TABLE RESOLUTION 088 Q DYENB ENABLE DAILY LDN HISTORY Q 89 Q PRNRPT DATA REPORT x Q 90 Q PRNLOG R S AND CAL LOG x B 18 Model 820 Technical Reference Manual 091 SETUP REPORT x Histogram Reports The RMS Peak and UWPk histogram reports have been implemented with this revision The unformatted reports have also been developed and the format is the level of the first bin followed by the number of samples in each bin in hex 0 9 amp There are 1024 RMS bins 128 Peak and UWPk bins this corresponds to 1 8th dB resolution for RMS and 1dB reso lution for the peak tables Q92 Q PRN RMS HISTOGRAM TABLE x Q 93 Q PRN RMS HISTOGRAM TABLE LOW VALUE n 094 Q PRN RMS HISTOGRAM TABLE HI VALUE n Q95 Q PRN RMS HISTOGRAM TABLE RESOLUTION x Q 96 Q PRN PEAK HISTOGRAM TABLE x Q97 Q PRN PEAK HISTOGRAM TABLE LOW VALUE n Q 98 Q PRN PEAK HISTOGRAM TABLE HI VALUE n Q99 Q PRN PEAK HISTOGRAM TABLE RESOL x Q 100 Q PRN UWPK HISTOGRAM TABLE x 101 Q PRN UWPK HISTOGRAM TABLE LOW VALUE n Q 102 Q PRN
64. It is characterized by changes in density pressure motion and temperature as well as other physical quantities Not all rapid changes in the medium are sound wind noise since they do not propagate The auditory sensation evoked by the oscillatory changes Difference between sound and noise Sound 1s the physical phe nomenon associated with acoustic small pressure waves Use of the word sound provides a neutral description of some acoustic event Generally noise is defined as unwanted sound It can also be defined as sound that causes adverse effects on people such as hearing loss or annoyance It can also be defined as the sound made by other people In every case noise involves the judgment of someone and puts noise in the realm of psychology not physics Rules 1 Use word sound to describe measurements to remove the emo tional overtones associated with the word noise Some sound met rics use noise in their name and it is proper to use the name as it is It is the total sound energy of the actual sound during a specific time period It is expressed in Pascals squared seconds T SE pi coat T where is the sound pressure and T is the Measurement Duration specific time period When applied to hearing damage potential the equation is changed to where k is the Exposure Factor See Exchange Rate Standard ANSI 51 25 Model 820 Technical Reference Manual C 13 SE Sound Exposure
65. MB UNLOCK Q 204 Q IONAME FILENAME cecccccc Q 205 Q ERCHK ENABLE ERROR CHECKING I O Model 820 Technical Reference Manual B 21 Error Checking I O The error checking I O protocol verifies that commands and data are transferred without errors To enable error checking the command or 5205 1 com mand is used To disable error checking two CR characters in a row may be sent if not in the Modem Mode or the S205 OF command is sent The F is the check character for the S205 0 command A detailed description of the protocol is available from Larson Davis and the latest revisions of software utilize the protocol Q 206 Q TBLMODE Ln table mode Overall Daily Q207 Q NFLVL NOISE FLOOR LEVEL This parameter is set to the noise floor of the instrument so that it can properly indicate Near Noise Floor messages when within 10dB of the noise floor It is also used with NF Compensate Q208 which will place the Model 820 in an extended Linearity Range Mode The true noise floor of the entire system must be measured and entered in Q207 This will vary with the selected input weighting or microphone sensitiv ity An equivalent microphone capacitance can be used after calibration to determine the noise floor It may also be possible to remove the microphone bias to obtain this value When properly set up the linearity range can be increased by
66. Model 820 Sound Level Meter Technical Reference Manual 9 ARSON DAVIS A PCB PIEZOTRONICS DIV Model 820 820 SLM cele ess eee eese OO Technical Reference Manual Larson Davis a division of PCB Piezotronics Inc 1681 West 820 North Provo UT 84601 1341 24 Hour Hotline 716 926 8243 Toll Free US 888 258 3222 www larsondavis com 1820 01 Rev D Copyright Copyright 2009 by PCB Piezotronics Inc This manual is copyrighted with all rights reserved The manual may not be copied in whole or in part for any use without prior written consent of PCB Piezotronics Inc Disclaimer The following paragraph does not apply in any state or country where such statements are not agreeable with local law Even though PCB Piezotronics Inc has reviewed its documentation PCB Piezotronics Inc makes no warranty or representation either expressed or implied with respect to this software and documentation its quality performance merchantability or fitness for a particular purpose This documentation is subject to change without notice and should not be construed as a commitment or representation by PCB Piezotronics Inc This publication may contain inaccuracies or typographical errors PCB Piezotronics Inc will periodically update the material for inclusion in new editions Changes and improvements to the information described in this manual may be made at any time Equal Opportunity Employer PCB Piezotroni
67. Peak Exceedance located is a field where six items of information are available d Parameter 64 UWPK Exceedance Respectively with the controlling parameter these are listed to the e Parameter 112 Overload current left If these parameter values have been triggered the will f Parameter 160 O OVLD overall overload appear to indicate that the record contains information related to that occurrence 5 2 Taking a Measurement Model 820 Technical Reference Manual Step 4 Press key again for the second screen Step 5 Press key for the third screen Step 6 Press key for the fourth screen Step 7 The next screen addresses the Alarm time and cur rent temperature Press key and the fifth screen will appear The Peak and Unweighted Peak are displayed here Note that even in the stop mode the Model 820 continues to display the detected values on the upper right hand side of the screen The numbers on the left are the highest during the measurement and the values on the right are the current Peak Unweighted Peak The Leg values are shown here to be 85 5 dB C weighted the mea surement ran for nearly four min utes Should one of four letters OVLD flash intermittently with the stick figure an Overload has occurred in this measurement see Chapter 7 The SEL level using exchange rate is 109 1 dB and the duration
68. R 100 LOGIC2 Logic Output 2 State On Off unused R 101 REPORT Report Number nnnnn R 102 PAGE Page Number nnnnn R 103 _PRNLINE Printer Line Number nnn R 104 _CALTIME Calibration Date Time ddmmmyy hh mm ss 105 _CHKTIME Cal Check Date Time ddmmmyy hh mm ss R 106 _OFFSET Cal Offset nnn n R 107 _CHKLVL Cal check Level nnn n OFFSET R 108 _RMSEX RMS Exceedance Flag 1 R 109 RMSEX2 RMS Exceedance Flag 2 R110 _PKEX PEAK Exceedance Flag R111 _UWPKEX UWPK Exceedance Flag R112 OVLD System Overload Flag R 113 _EXXR Excd Exchange Rate Text R114 _IVXR Intv Exchange Rate Text R 115 _AUTOADV Auto Advance History Ind R 116 131 unused unused variable R 132 _DYMIN Today s Minimum Level nnn n dB R 133 _ Today s Maximum Level nnn n dB R 134 _DYPEAK Today s Peak Level nnn n dB R 135 DYUWPK Today s UWPk Level nnn n dB R 136 _DYRNTIM Today s Runtime hh mm ss mm ss ss R 137 _ALMTIM Next Alarm Time hh mm R 138 _IVTIME Interval Date and Time of Occurrence ddmmmyy hh mm ss R 139 _IVDUR Interval Duration hh mm ss mm ss ss R 140 _IVLINT Interval Lint nnn n dB R141 _IVSEL Interval SEL nnn n dB 142 _IVMAX Interval Lmin nnn n dB R 143 _IVMIN Interval Lmax nnn n dB R 144 _IVPEAK Interval Lpeak nnn n dB 145 _IVUWPK Interval UnWeighted Peak nnn n dB R 146 _HISTLEQ AU
69. TO SEND HISTORY LEQ nnn n dB R 147 149 unused unused variable R 150 RUNCNT Number of RUNS amp CONTINUES nnnnn Model 820 Technical Reference Manual B 9 R151 _POFAULT Power On Fault Cause Character D Data Checksum Corrupt E EEPROM Checksum Corrupt Key Reset 4 RESET 4 On P Parameter Checksum Corrupt O Opcode Error R RAM Setup Register Corrupt T Test Memory Corrupt W Watchdog Reset An indicator has been added to the ON display on the top line of the 8205 display to show faults that were detected by the power on test procedure The R151 command will display the fault character to a computer The indicators are 152 _INRMS Internal RMS detector level nnn nn dB R 153 _INPEAK Internal PEAK detector level nnn nn dB 154 _INUWPK Internal UwPk detector level nnn nn dB 155 _KEYCNT Free Bytes in Keyboard Stack nnn R 156 _BGTIM Background Leq Time hhhhh mm ss ss 157 _CALSTAT Calibration Status lt lt UnStable gt gt R 158 _MEMSIZ Total number of bytes for histories nnnnnnn R 159 _ Memory Available in percent nnn nn R 160 _O OVLD OVERALL OVERLOAD FLAG 161 unused unused variable R 162 _O SE Overall Sound Exposure nnnnn n a The number of keys in the keyboard stack is available with the R155 command This is used with keyboard simulation to prevent the loss of keys Model 820 Technical Reference Manual
70. VL CAL LEVEL Q 36 Q CALSN CALIBRATOR S N Q37 Q AUTOCAL AUTO CALIBRATION MODE Q38 Q CALTIM AUTO CAL TIME Q39 Q DETC DETECTOR Q 40 Q WGHT FREQUENCY WEIGHTING Q HPASS HIGH PASS FILTER unused Q42 Q LPASS LOW PASS FILTER unused Q 43 Q MICV MIC POLARIZATION unused Q 44 Q REFLVL RELATIVE LEVEL REFERANCE Q 45 Q CXRATE CURRENT EXCHANGE RATE Q 46 Q CTHOLD CURRENT THRESHOLD Q47 Q CCRIT CURRENT CRITERION Q 48 Q OXRATE OVERALL EXCHANGE RATE Q 49 Q OTHOLD OVERALL THRESHOLD Q 50 Q OCRIT OVERALL CRITERION 051 Q DOSET DOSE PERIOD 052 Q LDLXRATE LDL EXCHANGE RATE Q53 Q LDLTHOLD LDL THRESHOLD Q 54 Q LDLCRIT LDL CRITERION Q 55 Q LNNI Lnn 1 PERCENT Q 56 Q LNN2 Lnn 2 PERCENT Q57 Q LNN3 Lnn 3 PERCENT Q 58 Q LNN4 Lnn 4 PERCENT Q 59 Q LNN5 Lnn 5 PERCENT Model 820 Technical Reference Manual B 17 Q 60 Q LNN6 Lnn 6 PERCENT 061 Q RMSTHI RMS EXCD LEVEL 1 Q62 Q RMSTH2 RMS EXCD LEVEL 2 Q 63 Q PKTH PEAK EXCD LEVEL Q64 Q UWTH UWPK EXCD LEVEL Q 65 Q HYST EXCD HYSTERESIS Q 66 Q EXENB ENABLE EXCD HISTORY Q67 Q EXXRT EXCD EXCHANGE RATE Q 68 Q EXMIN EXCD MINIMUM DURATION Q 69 Q EXHENB EXCD TIME HIST ENABLE Q 70 Q EXPER EXCD TIME HIST PERIOD Q71 Q EXADEN EXCD SAVE A D ENABLE unused Q72 Q IVENB ENABLE INTV HISTORY Q73 Q IVXRT NTV EXCHANGE RATE 074 Q IVTHOLD NTV THRESHOLD Q75 Q IVPER NTV PERIOD Q 76 Q IVSYNC INTV T
71. a minimum of 5 sec and a maximum of the time programmed 20 Power Save Auto Off Manual Off Audio Off Auto Off If in the Stop mode and if no keys are pressed or commands given for 12 min the Model 820 will turn off automatically Manual Off The Model 820 will not turn off until the OFF key is pressed a computer OF F command is given or the batteries become low Audio Off Not available on the Model 812 Model 820 Technical Reference Manual 8 9 Timer 21 27 These parameters are used when Start and Stop of measurements are to be controlled by the clock No Prompt Entry Comment 21 Timer Mode Off Block 1 day 2 Block Run Time 1 on Run Date to day Stop Time 1 on Stop Date 1 day Run Time 1 to Stop Time 1 each day from Run Date to Stop Date 2 day Run Time 1 to Stop Time 1 and Run Time 2 to Stop Time 2 each day from Run date to Stop Date 22 Timer Run Date dd mm yy See Timer Mode comment 23 Timer Stop Date dd mm yy See Timer Mode comment 24 Timer Run Time 1 hh mm ss See Timer Mode comment 25 Timer Stop Time 1 hh mm ss See Timer Mode comment 26 Timer Run Time 2 hh mm ss See Timer Mode comment 27 Timer Stop Time 2 hh mm ss See Timer Mode comment Lock 28 34 These parameters limit access of certain functions to those with the correct password Step 1 After setting password and lock options exit the For complete instruc
72. a user set period Time history sampling periods are user selectable from 32 samples second up to one sample every 255 minutes Quartz clock calendar system for data annotation Calibration from front panel using an appropriate calibra tion source Easy one step reset of measurement Battery level indication Standard 9V internal alkaline battery life of more than 16 hours or external power using Larson Davis cable 035 for longer measurements RS 232 computer and modem interface standard All func tions fully programmable Comes complete with PC SWW_SLM_UTIL software for data retrieval and translate binary files to ASCII format Other PC software also avail able Large two line 32 character high contrast LCD display Small 33cm 7 5cm x 2 5 13 H x 3 W x 1 D and lightweight 370g 13 oz including microphone and bat tery Rugged ABS case with EMI and RFI protection Environmental enclosures available for system security and protection from inclement weather Durable membrane keypad 1 6 Features Model 820 Technical Reference Manual Model 820 Components A layout of the Model 820 is shown below Microphone Microphone Preamplifier LCD Display 4 _ Keypad O00 a Connector AC DC Out Connector Cal Heater Port Optional Connector Serial Battery Port Compartment Figure 1 1 Model 820 The Model 820 is a convenient hand held
73. al Getting Started 1 16 ADPO008 E 1 820 SYSTEM Note Those items marked with are standard included accessories WS005 Windscreen with birdspikes Rainhat with Z electrostatic actuator FE u2 inch Microphone PRM2101 2106 7 8 PRM828 CCS009 Soft Case 4 Conductor CBLO34 6 EXCXXX 20 Max CBLO04 6 AC Out black DC Out red CBL009 020 820 01 required Battery powers 2101 heater and EA 1 002 12 7 E EPS012 Environmental Case Va 5013 Environmental Case w Battery Software SWW SLM UTIL SWW SLM LINK SWW ENV SWW REM SWW NMS SWW ACS Larson Davis WEB Page Shielded Battery to power 820 CBLO35 4 o 3 alligator clips 3 PSA005 AC DC Adaptor Figure 1 4 820 System Diagram CBL116 1 5 Battery CBL116 1 5 Getting Started 5 001 next SLM CBLO4O 12 5 001 CBLO77 6 optional CBLO33 6 Desktop Computer L Laptop Computer Serial Printer B CBLO77 6 optional Model 820 Technical Reference Manual Battery Installation To insert the 9 volt battery in the Model 820 remove the battery cover at the lo
74. all Leq of all samples that were not an event Model 820 Technical Reference Manual Taking a Measurement 5 13 BATTERY In Chapter 2 we accessed the Battery information to check the amount or voltage remaining in our battery This function has additional screens available The first two indicate the amount of voltage remaining and the second shows the information related to the last revision Step 1 Access the Battery display by pressing SHIFT and Press the gt key to access the second screen Step 2 Press key and a screen similar to the follow ing will appear MEMORY Memory will be addressed in Chapter 9 but it would be well to examine the key functions here Standard memory size is 250 KBytes Three screens are available from this function Step 1 Press GHIFT and 0 A screen similar to the fol lowing will appear 5 14 Taking a Measurement The Revision date is shown Eight additional screens are avail able from this function Warning or Error messages encountered dur ing normal operation will be dis played here in the order they happen They are accessed by either the 4 and gt keys or the and x keys which will scroll only the warning messages This screen shows the percentage of memory left of the total avail able 248837 divided by 250793 99 2196 Model 820 Technical Reference Manual Step 2 Press the M key to access the nex
75. ameters 4 7 Step 5 To exit the setup mode press AC DC Output AC and DC is accessed by the use of the optional CBL042 or by using a stereo miniphone plug as shown in figure 4 5 The DC output provides a voltage from the RMS detector that is proportional to the sound level The scale is 20 3 mV dB The output voltage is 0 3 volts with an output impedance of 600 The AC output gives an AC signal proportional to input signal and can be Flat or A and C weighted It is used to record input signal to the Model 820 note Appendix A for more details CBLO42 AC Output black DC Output ring AC Output tip Bion Ground sleeve DC Output red Figure 4 5 AC DC Output Connector 4 8 AC DC Output Model 820 Technical Reference Manual Performing a Measurement Reading the Data With the basic parameters set and the instrument calibrated as discussed in Chapters 3 and 4 you are ready to take a mea surement and examine the readings from the data collected Taking an actual measurement with the Model 820 only requires pressing the or RUN STOP key In this chapter we will Take a measurement Examine and briefly explain the function keys associated with the measurement ic ENERE PR CH and GN Stopping the measurement Taking a Measurement This section will address measurements and the information available during and after the measurement has been taken The most
76. and date The instrument will not allow itself to be turned off until in Stop mode This feature will insure that no important data is lost Model 820 Technical Reference Manual Turning Off the Model 820 2 11 Calibration Because of variation in microphone sensitivities a sound level meter must be calibrated to a reference sound level for accu rate measurements This is easily performed with the Model 820 You will need a calibrator with an appropriate adapter for the Model 820 microphone such as the Larson Davis CAL200 This Larson Davis calibrator outputs 114 dB or 94 dB with respect to 20 uPa and at a frequency of 1000 Hz At this frequency the relative response for A and C weightings is the same NOTE A precision calibrator is not necessary for this part of the tutorial but you should make it a regular practice to perform an instrument calibration before and after you take actual measurements in the field However you do not have to recalibrate the Model 820 when you change the settings Please note that if you use a calibrator which uses another fre quency some corrections may be required depending on the weighting The output level and the frequency of your calibra tor should be listed on its label Use this level with specific environmental and weighting corrections to calibrate the Model 820 level In order to perform calibration the Microphone Polarization Voltage needs to be properly set Calibrating th
77. ariable associated with the index Use var_no of 0 to define the last group list index when n lt 8 Example 1 4 assigns current SPL to first group index G2 15 er assigns Lmin to the second index G3 19 cr assigns Lmax to the third index G4 0 terminates group command programming After programming this group read list the response to GO is 59 5 38 6 102 2 the SPL Lmin and Lmax Setting Parameters All commands begin with S See Chapter 8 for a list of all the parameters and their settings Note that the parameter numbers are for both Set S and Query Q commands There are four types of parameters Numeric Indexed Character strings Template Brackets indicate optional characters and operands cr carriage return If line feed space Numeric Parameters Syntax Response S et item number parameter valuecr If B 12 Model 820 Technical Reference Manual Example 562 120 sets RMS Excd Level 2 to 120 Indexed Parameters Indexed parameters can be set in two ways a index number and b actual indexed parameter value a Index Number Syntax Response S et item_number index_number cr If Example S9 3 sets parameter 9 Baud Rate to third possible value of 2400 S66 1 sets Excd History Enable to Yes 584 0 sets Hist Period Units 1 325 584 1 sets Hist Per
78. ata Logic recalculation can be started with a LDLVALID I O Read Command When the Model 820 is RUNNING the Valid condition will remain in effect for 1 second The JLDLVALID Read Command provides three responses LDL Valid Calculating and LDL Invalid NOTE The exceedance Leq R68 and exceedance time R69 include data from qualified events that are stored in the EXCD History If an event is discarded because it was shorter than the minimum duration then it will not be included in these values B 8 Model 820 Technical Reference Manual R 70 BGLEQ Background Leq nnn n dB R 71 85 unused unused variable R 86 _BATT Battery Level nnn R 87 _BATTSRC Battery Source INT EXT 88 _ Temperature nnn n R 89 _SERNUM Serial Number R90 _REVNUM Software Rev amp Rev Date n nnn ddmmmyyyy R91 _FREEMEM Free Memory nnnnnnn R92 RECLOG Number of RUN STOP Records nnnnn R93 RECEXCD Number of EXCD Records nnnnn R94 RECINTV Number of INTV Records nnnnn R95 _RECHIST Number of HIST Records nnnnn R 96 _RECDALY Number of Daily Records nnnnn R97 RECCAL Number of Daily Records nnnnn 98 n _ERRMSG Error Message List is the error list number 1 8 1 being latest error or nnn nnn nnn if n 0 or omitted then the 8 error codes are output as number R99 LOGICI Logic Output 1 State On Off unused
79. ay from line 15 Time History bytes day from line 22 Run Log bytes day 2 nx20 X 20 n number of Run Log records day n x 20 bytes record Calibration Log bytes day 1 17 X 17 n x 17 bytes record Setup RAM Registers bytes used 0 nx506 n number of registers stored day n x 506 bytes record TOTAL bytes used day Sum lines 23 29 20898 Model 820 s Memory Size 252661 See SYSTEM b 251 805 TOTAL Run Time in days Divide line 34 by 33 12 05 until out of memory Model 820 Technical Reference Manual Estimating Memory Usage 9 5 CHAPTER Printing a Report The Model 820 allows for tailored reports of data during and after measurements In this chapter we will access the printing option parameters for the following topics Normal Printouts Printing Reports Real time Printing Normal Printout Parameters Before proceeding with printing baud rate needs to be deter mined and entered Set parameter 9 to proper baud rate deter mined by type of printer used If after starting printing bad information is printed baud rate or printer type is probably set incorrectly To cancel printing hit and 57 Normal printouts can be accessed from outside the SETUP mode by following these steps Step 1 Turn the Model 820 on and press The follow ing display will appear briefly and then scroll auto matically through several options Step 2 To ta
80. ble T Advance Advance a number of records from present record number If no num_record number of records is provided 1 15 assumed Syntax Response A dvance num_record history_no cr If Example A9 5 current record is 17 calibration history s record 26 17 9 is located B 24 Model 820 Technical Reference Manual Backup Backup a number of records from present record number Syntax Response Backup num_record history_no cr If If no num_record number of records is provided 1 is assumed Example B9 5 current record is 17 locates calibration history record 8 17 9 Find Find record number directly Syntax Response F ind rec no history no cr If Example F9 5 locates calibration history record 9 Generally one uses the Find command to get to the first record F1 2 and the Advance command A to move up through the records History Data Variables Exceedance History Variables Brackets in the syntax indicate optional characters and oper ands Syntax Response E xceedance var_no Example 9 Overload count from current record Model 820 Technical Reference Manual B 25 El Date and Time of Occurrence ddmmmyy hh mm ss E2 Duration hh mm ss mm ss ss E3 Lint nnn n dB E4 SEL nnn n dB 5 Lmax nnn n
81. ceedance levels history interval time history and daily history Chapter 8 Parameters A complete listing of all parame ter items and an explanation of their basic functions Chapter 9 Memory Usage Sizing parameter needs to insure adequate memory for any given measurement Chapter 10 Printing a Report Turning gathered data into a printed report Appendix A Specifications A listing of acoustic elec tronic environmental and physical characteristics of the Model 820 Appendix B Model 820 Serial Port Interface Remote Con trol Setting interface commands with their syntax Appendix C Glossary Definitions of key terms and con cepts used in this manual Appendix D Index Alphabetical listing of all major com ponents of this manual 1 2 About This Manual Model 820 Technical Reference Manual About This Chapter Specifically this introductory chapter covers the following topics Formatting Conventions Explanation of the fonts and other formatting conventions used in this manual Model 820 Features A listing of the featured characteris tic and capabilities of the Model 820 Model 820 Components Description and diagrams of the Model 820 external parts Getting Started Instructions for unpacking a listing of accessories and optional equipment and initial setup Formatting Conventions This manual uses the following formatting conventions Functions accessed by pressing a key on th
82. cs is an equal opportunity employer and does not discriminate on the basis of race color religion gender national origin disability or veteran status Please examine your instrument and record the following information below You may be asked to give this information in any future communications you have with PCB Piezotronics Inc Customer Service In the U S call toll free 888 258 3222 International customers 1 716 926 8243 FAX 1 716 926 8215 Email techsupport LarsonDavis com Worldwide Web www LarsonDavis com Record of Serial Number and Purchase Date System 820 Serial 828 Pre amp Serial Microphone Model Microphone Serial Purchase Date Recycling Larson Davis Inc is an environmentally friendly organization and encourages our customers to be environmentally conscious When this product reaches its end of life please recycle the product through a local recycling center or return the product to Larson Davis Inc Attn Recycling Coordinator 1681 West 820 North Provo Utah USA 84601 where it will be accepted for disposal Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Table of Contents Introduction 1 1 About 4 aae eee eee 1 1 About This Chapter rr RR RR DS NE 1 3 Formatting 1 3 8 teo GI Re eon qb eed 1 5 Model 820
83. ctions Model 820 1 2 Hysteresis 8 14 I o oce rede 5 4 Indexed iiie deo B 13 Indexed Parameters B 13 Interal Index International Electrotechnical Commission IEC Interval History parameter settings Interval Variables Intrusion alarm Error Checking K Key date parameters day ees 8 10 Index Di Time History Time key functions time parameters Ue glossary Leq Eqivalent Level Leq Equivalent Level Lmax MS 2 5 parameters 5 5 Lmin 2 5 parameters 5 5 LN LM Statistical Levels 8 13 Ao 5 8 Ky so cest eaae ee Raves 2 6 LN Statistical Levels 8 13 LOCK arcs doit atia eic 8 10 2 4 Log 2 2 4 Logged Dated Logic see LDL 2 7 M Measurement oerte 5 1 Performing 5 1 Stopping ehe erre 5 15 Meas
84. culate the number of bytes required for each record type Multiply by the number of records expected per day Sum these values and this is the number of bytes required per day Divide this value into the amount of available memory in the Model 820 see GHIFT and this is the number of days the Model 820 can gather data As an example let s assume a job requires monitoring the noise made by trucks coming and going from a factory near a residential area From an initial site survey it is discovered that all trucks are over 65dBA at the boundary of the road and resi dential property and that there seems to be a truck passing the site every 3 minutes The occupants of the residential area want to know how many trucks are traveling this road and why they are disturbed by some more than others The Exceedance Function will be used to detect events over 65dBA and there is expected 20 events per hour or 240 per day 20 events hour time 12 hours day assuming that the plant operations will be reduced during the night Statistics based on hourly intervals and a one minute time history are desired to identify distur bance pattern The following completed work sheet shows the calculations for this example Model 820 Technical Reference Manual Estimating Memory Usage Exceedance Memory Estimation Bytes needed Basic Exceedance Record 32 Excd Time Hist 21 n n estimated of samples 129 bytes max 20sec Excd TOTAL Bytes Exc
85. d Frequency Hz rad sec C 6 the change in sound level corresponding to a doubling or halving of the duration of a sound level while a constant percentage of cri terion exposure is maintained in the table below Standard ANSI 12 19 The rate and the factors are given Exchange Rate Q Exchange Rate Exposure Factor k Factor q 3 01 10 1 4 13 333 19 5 16 667 60 6 02 20 50 There are two types of far fields the acoustic far field and the geo metric far field Acoustic Far Field The distance from a source of sound is greater than an acoustic wavelength In the far field the effect of the type of sound source is negligible Since the wavelength varies with fre quency See the definition of Wavelength the distance will vary with frequency To be in the far field for all frequencies measured the lowest frequency should be chosen for determining the dis tance For example if the lowest frequency is 20 Hz the wave length at normal temperatures is near 56 ft 17 m at 1000 Hz the wavelength is near 1 1 ft 1 3 m See the definition of Acoustic Near Field for the advantages of in the acoustic far field Geometric Far Field The distance from a source of sound is greater than the largest dimension of the sound source In the far field the effect of source geometry is negligible Sound sources often have a variety of specific sources within them such as exhaust and intake noise When
86. d is to keep the instrument inside a sealed foam insulated case or bag with desiccant silica gel available at photographic equipment stores or from Larson Davis Alternatively you may use an external power source via pin 1 GND and pin 4 of 5 pin connector To do this order cable 035 from Larson Davis The Model 820 accepts 7 16 Vdc 30 is internally fused at 0 5 A Preparing to Use the Model 820 Connecting the Mic Preamp Before powering the SLM carefully thread the microphone on the preamplifier The microphone bias voltage is not dangerous but installing or removing the microphone with the instrument on may damage the electronics Insert the 828 in the nose cone or extension cable by lining up the latch button with the channel in the mating connector The small black dot should click and protrude at the base of the 828 after insertion It must be depressed completely to remove the preamplifier from the mating connector 1 18 Getting Started Model 820 Technical Reference Manual Overview to Model 820 Once your Model 820 is unpacked and connected to a battery or external power supply you can turn it on and take simple measurements In this chapter we discuss the following Understanding the Model 820 Keypad Understanding the Model 820 Screen Getting to Know Screen Symbols Turning on the Model 820 Checking the Battery Voltage Turning off the Model 820 Understanding
87. d sum lines 1 4 gt gt gt gt gt gt Anticipated Day Enter Number gt gt gt gt gt gt TOTAL Excd Bytes Day lines gt gt gt gt gt gt Interval Memory Estimation Bytes needed Basic Interval Record Intv Save Ln s Yes Prm 77 Intv Save Ln Table TOTAL Bytes Intv sum lines 6 8 gt gt gt gt gt gt Anticipated Intv Day Enter Number gt gt gt gt gt gt TOTAL Excd Bytes Day Multiply lines gt gt gt gt gt gt Daily History Memory Calculation Bytes needed Basic Daily Record 175 Daily Save 6 Ln Values 18 Daily Save Ln Table 440 TOTAL Daily Bytes Day ion 12 gt gt gt gt gt gt Line Time History Memory Calculation Bytes Bytes Hist Resolution Hist Save Peak 16 1 0dB No 1 9 4 Estimating Memory Usage Model 820 Technical Reference Manual Time History Memory Calculation Bytes 0 1dB No 1 0dB Peak UwPk Max Wind 0 1dB Peak UwPk Max Wind TOTAL bytes Hist Record Select the appropriate of bytes from lines 16 19 Hist Records Day Enter Number Calculate 24 hours divided by Hist Period in hours i e 24 60 sec 3600 sec per hour 1440 TOTAL Hist Bytes Day 23 and 24 copy copy to Memory Use per Day Calculation Bytes Exceedance History bytes day from line 5 Interval History bytes day from line 11 Daily History bytes d
88. dB E6 Lpeak nnn n dB E7 UnWeighted Peak nnn n dB E8 Peak Exceedance Count nnn E9 Overload Counts nnn E10 Illegal Indication 17 Excd Time Hist Samples nnn E 18 lt n gt Excd Time History nnn n dB E 19 lt n gt Excd T H Time SSS SS E 20 lt n gt Excd T H Number nnn 21 lt gt Excd Bargraph SIGIR ICI SISA ACR ACC AI I E25 EXCD SYMETRY nnn nn E101 Excd Variables 1 10 Macro E 102 Excd Time Hist 17 18 Macro Interval History Variables Brackets in the syntax indicate optional characters and oper ands Syntax Response I nterval var_noIntv_var Example 19 5 current record is 17 B 26 Model 820 Technical Reference Manual RMS Exceedance count in record 12 Example 19 5 current record is 17 RMS Exceedance count in record 22 1 Date and Time of Occurrence ddmmmyy hh mm ss 12 Duration hh mm ss mm ss ss 3 Lint nnn n dB 4 SEL nnn n dB 15 Lmin nnn n dB 6 Lmax nnn n dB 7 Lpeak nnn n dB 8 UnWeighted Peak nnn n dB 19 RMS Exceedance Count nnn 110 Peak Exceedance Count nnn 111 UnWeighted Peak Excd Count nnn 112 Overload Counts nnn 13 nn 1 Lnn 14 Ln 1 nnn n dB 15 nn 2 Lnn 16 Ln 2 nnn n dB 17 nn 3 Lnn 18 Ln 3 nnn n dB 119 nn 4 Lnn 20 Ln4 nnn n dB 21 nn 5 Lnn 122 Ln 5 nnn n dB 23 nn 6 Lnn
89. daily report NOTE Parameters 168 173 for additional printing options Additional System Functions 152 154 161 The functions below apply to the LDL Model 820 when used in remote applications such as in airport or perimeter noise monitoring systems Requires Model 820 option 01 These parameters are for control in Model 2101 No Prompt Entry Model 820 Technical Reference Manual Comment 152 E A Cal Tone No Yes Automatic electrostatic actuator cali bration tone control 820 OPT 01 must be installed 153 Heater On Yes No 154 Modem Mode No Yes Select if Model 820 s RS 232 port is connected to modem 155 Deal Out Mode None EXCD ALRM Instrument automatically dials out if Both EXCD RMS Exceedance level 2 is Exceeded ALRM Enclosure intruder alarm is triggered or Both 156 Phone 157 Monitor Number 0 127 Monitor Identification number 158 M Init Modem Initialization Sequence 159 Power Mode Normal Ext CO Normal meter uses internal battery unless greater external voltage is also applied Ext CO external cutoff when exter nal power falls below 10 5 V meter turns off to prevent battery damage 161 Timed EXCD Per mm ss Exceedance Time history is recorded from 10 samples before exceedance to 10 samples after this period 162 EXCD Trigger Level Bypass Bypass Enables a variable threshold 163 EXCD Time Start Max Start The
90. e or a to view the next or previous exceedance Setting PassBy Functions The PassBy Function 1s a special exceedance event detector that measures the Lmax Leg and SEL of the highest event to raise and lower S 10 dB in SPL It is used to capture single events such as a vehicle or aircraft passby or other event noises such as blasts or gas getting noise In addition to the levels measured the date and time of the Lmax and the dura tion of the event are recorded The maximum duration of passby event may be 1 or 2 minutes depending on the shape of the event Maximum passby duration will be reduced if exceedance is reduced Step 1 To enable the Passby function turn on the Model 820 and then press 5 Modify 1 6 0 and Enter The screen will show either of two options Level PassBy Step 2 Press and then press M to PassBy and then press Enter When the Exceedance History and Passby parameter 66 and 162 is enabled a Passby record will be created whenever a delta 10dB event is detected See Figure 7 2 The occurrence time or Maximum Level must be equal to or greater than the RMS EXCD LVL 1 parameter 61 7 12 Setting and Viewing Advanced Functions Model 820 Technical Reference Manual Passby s Max Occurrence Time Start of Exceedance Te Duration Figure 7 2 Passby Diagram After taking a reading with Passby enabled you may wish to examine the Passby event
91. e 16 and C16 not applicable to the Model 820 41 AC Weighting Flat Wght F 20 F 20 Flat Level with 20 dB gain W 20 W 20 Weighted with 20 dB gain 42 Unweighted Peak Flat C 43 Mic Polarization 10 28 200 This selects the polarization voltage Voltage for the microphone Chose 28 or 200 V for condenser type microphones and 0 V for pre polarized microphones electret 44 Reference Level 0 to 255 dB measured level reference level rel ative level used in some functions 45 Currant Exchange 3dB 4dB 5dB 6dB Exchange rate for currant TWA or Rate 1 Dose readings For OSHA use 5dB 46 Current 0 to 255 dB Levels above threshold are integrated Threshold 1 into currant TWA or Dose readings For OSHA use 80 dB 47 Currant 0 to 255 dB 100 dose if this level is maintained Criterion 1 for full dose period For OSHA use 90 dB 48 Overall 3dB 4dB 5dB 6dB Exchange rate for overall TWA or Exchange Rate 2 Dose readings 49 Overall 0 to 255 dB Levels above threshold are integrated Threshold 2 into overall TWA or Dose readings 50 Overall 0 to 255 dB 100 dose if this level is maintained Criterion 2 for full dose period 8 12 Model 820 Technical Reference Manual Dose 51 The noise exposure Dose may be calculated with three differ ent set of parameters CURRENT OVERALL and LDL See section on occupational noise for additional information The dose displayed with the DOSE key is Dose 2 No Promp
92. e P selects pulse dialing T selects tone dialing will pause dialing for 2 s space or used to make the number more readable Example T9W 1 412 555 1212 indicates to use tone dialing dial 9 for an outside line wait until the dial tone is detected and then dial the number Monitor Number The monitor number is used to specifically address the moni tor B 34 Model 820 Technical Reference Manual 820 Phone Dialing Procedure The Model 820 dialing process is as follows Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 The Model 820 recognizes an exceedance or low memory condition The Model 820 asks the modem to dial the phone number The modem informs the Model 820 that a connec tion has been made The Model 820 modifies its baud rate to that of the connected modem If the con nection is unsuccessful the procedure is retried in 4 min The Model 820 sends the following announcement 820 82040123 001 2 enter where 0123 is the Model 820 s serial number 001 is the monitor number entered and 2 is a flag 1 Alarm 2 Exceedance 4 Low Memory More than one of these can be set at a time in which case x is the sum of all set flags The Model 820 awaits a response code which should be 820 A0123 11111111 enter where 0123 is the Model 820 s serial number and 11111111 is the Lock Combination parameter 28 which is required whether or not the Model 820 is currently locked If the r
93. e Model 820 Microphone Polarization Voltage is preset by Larson Davis at 200 volts Should this parameter be incorrect the Model 820 will not calibrate correctly Step 1 Check the microphone polarization by looking at Model 820 Technical Reference Manual Calibration Step 2 Should the brackets contain a value other than 200 Step 3 Step 4 3 2 setup parameter 43 To do this turn on the Model 820 press 5 Modify 4 and 3 and Enter The following display will appear e g 28 or 0 press until the value 200 appears and then press Enter If you are using a pre polarized microphone this parameter should be set to 0 Press Cancel to return to the main screen To begin the calibration process check or insert the new calibration level given in parameter 35 To do this press 4 Modify 3 and 5 then Enter The following screen will appear Calibrating the Model 820 The flashing f the Keyboard Sta tus Indicator displays which key functions are active This indicates that the function keys are used for different purpose in current func tion In this screen the value 200 is selected from three options 200 26 0 The Larson Davis Model CAL200 calibrator outputs 114 dB or 94 dB re20 uPa Note that the Model 820 automatically uses the C weight ing while calibrating This ensures a correct reading at typical cali bratio
94. e Model 820 keypad are shown with an icon for example Press and then press In step by step directions the process what you do is shown in the left column and the rationale why you do it with other cautions and comments are shown in the right column For example Microphone Polarization Voltage is preset by Larson Davis at 200 volts Should this parameter be incorrect the Model 820 will not calibrate correctly Model 820 Technical Reference Manual About This Chapter 1 3 Step 1 Check the microphone polarization To do this turn The flashing f the Keyboard Sta on the Model 820 press 5 Modify 4 and 3 and tus Indicator displays which key Enter The following display will appear functions are active This indicates that the function keys are used for different purpose in current func tion Step 2 Should the brackets contain a value other than 200 In this screen the value 200 is e g 28 0 press the until the value 200 selected from three options 200 appears and then press Enter 28 0 1 4 Formatting Conventions Model 820 Technical Reference Manual Especially important information is shown in italics for example To access items 48 50 Overall Exchange Rate Overall Threshold Overall Criterion press key Features The Larson Davis Model 820 meets the requirements of the American National Standards Institute ANSI 51 4 International E
95. e Noise Model 820 Technical Reference Manual C 17 Time Weighting Vibration Wavelength 1 Wavenumber k Dose as the actual unsteady sound over the same period If the Exchange Rate is 3 dB then the TWA is equal to the 15 1 where T T T is the Exchange Rate Factor It is used for hearing damage risk assessment Standard ANSI 12 19 The response speed of the detector in a sound level meter There are several speeds used Slow The time constant is 1 second 1000 ms This is the slowest and is commonly used in environmental noise measurements Fast The time constant is 1 8 second 125 ms This is a less com monly used weighting but will detect changes in sound level more rapidly Impulse The time constant is 35ms for the rise and 1 5 seconds 1500 ms for the decay The reason for the double constant is to allow the very short signal to be captured and displayed The oscillatory movement of a mechanical system generally taken to be solid It is used as a broad desciptor of oscillations The distance between peaks of a propagating wave with a well defined frequency It is related to the frequency through the follow ing equation KIO where c is the sound speed and f is the frequency in Hz It has the dimensions of length A number that is related to the wavelength of sound and is used to compare the size of objects relative to the wavelength or the time delay in sound propa
96. ed by pressing the shift key three times The number 3 appears in the lower right corner of the display indicating this panel is accessed Figure 4 4 3 Shift Level 3 Alpha numeric Keyboard 4 4 Setting Parameters Using Numbers and Other Characters Model 820 Technical Reference Step 1 Step 2 Step 3 Step 4 To enter a name for example turn the Model 820 on and press these keys to access the first name field Modify 0 2 Enter Press Press SHIFT Press SHIFT twice Model 820 Technical Reference Manual Setting Parameters Using Numbers and Other All but the last of these screens you have seen before This display is to set one of four custom instrument name screens which will appears each time you turn the instrument on Notice the parentheses begin to flash and the f changes to n and the L is underscored Larson Davis You may now enter the appropriate letters here by using the Alpha Character Keyboard Entry shown above The flashing n is replaced by S and will remain for five seconds At this time you may select any character from the S table press that key and it will replace the let ter at the cursor _ The cursor then moves to the next letter The n is replaced by 2 for five seconds Letters from the 2 panel are available for entry Step 5 Press SHIFT three times Step 6 Step 7 Step 8 Step 9 4 6 Exam
97. el 820 s large data memory relieves the user from the concern of data loss caused by memory limitations Furthermore measurements can be printed or transmitted at up to 19 2 K baud via RS 232 for further manipulation or archiving Despite its numerous functions the Model 820 is easy to use Annotated displays indicate units and measurement mode The single setup menu lets the user scroll through and program parameters or use an index key to modify specific information Multiple measurement setups can be stored in memory for later recall And of course complete setups can also be transferred from a computer 820 Block Diagram Slow Fast Impl Clock Timer lt 2 Micro RAM 0 28 200 V r Peak 1 256K Bias Supply 2 Internal Power 9V Battery Supply Weighted gt AC DC Output Indicates parameter number Flat 5 pin Connector e 20 dB Figure 1 3 Block Diagram 1 10 Model 820 Components Model 820 Technical Reference Manual The block diagram above shows how the Model 820 sound level meter merges state of the art analog circuitry a powerful microcomputer controller and a large amount of usable data memory The signal from the precision air condenser microphone preamplifier is input directly to the linear peak detector and through the selected A or C weighting filter to the root mean square
98. elected via parameter 40 Frequency Weighting The Weighted Peak Detector and DC Output frequency weighting always matches the RMS Detector frequency weighting A 4 Reference Level Model 820 Technical Reference Manual 2 The Unweighted Peak Detector frequency weighting is selected via parameter 42 UWPK Weighting therefore it can be set independent of the RMS Detector frequency weighting The Unweighted Peak Detector s typical FLAT fre quency response is shown in the table below 3 The AC Output frequency weighting is selected via parame ter 41 AC Out Weighting It can be set to Flat weighting or it can be set to match the RMS Detector frequency weight ing The AC output s FLAT frequency response is shown in the table below Unweighted Peak FLAT Frequency Response Unweighted Peak Unweighted Peak Unweighted Peak FEAT Weighting Weighting VELAT Weighting 10 3 4 160 0 0 2500 0 0 12 5 2 5 200 0 0 3150 0 1 16 1 7 250 0 0 4000 0 2 20 1 2 315 0 0 5000 0 2 25 0 8 400 0 0 6300 0 3 31 5 0 5 500 0 0 8000 0 4 40 0 3 630 0 0 10000 0 5 50 0 2 800 0 0 12500 0 8 63 0 1 1000 0 0 16000 0 9 80 0 0 1250 0 0 20000 1 2 100 0 0 1600 0 0 125 0 0 2000 0 0 AC Output FLAT Frequency Response Nominal AC Output FLAT Nominal AC Output FLAT Nominal AC Output FLAT Frequency Hz Weighting dB Frequency Hz Weighting dB Frequency Hz Weighting dB 10 7 6 160
99. ement was stopped by keystroke If a low battery had been the reason for the measure ment stopping BATT would have appeared To retain data already gathered the Model 820 will terminate the measurement when battery power becomes low With this item set to Yes the Interval Time History ITH is enabled Note Be sure that total memory requirements do not exceed available memory This parameter is the exchange rate used for each interval Set this to 3 dB for community noise and 5 dB for OSHA studies Setting and Viewing Advanced Functions 7 5 Step 3 Step 4 Step 5 Step 6 Step 7 7 6 Press to item 74 Intv Threshold You may find 80 dB preset but you may enter another value 0 255 Press the v to item 75 Intv Period Press and the numeric values for the interval period desired and then press Enter hh mm Press v to Time Sync item 76 for these choices Yes No Press the v to item 77 Intv Save L 5 The Choices are Yes No Press the to item 79 Intv Auto Stop The choices are Yes No Setting and Viewing Advanced Functions This sets the TWA threshold for the interval time history For hearing conservation purposes 60 dB is recommended For most commu nity noise purposes set this parameter to 0 or slightly above the noise floor This sets the period for the interval history A 1 second Interval may be selected by entering 00 00 The
100. esponse is incorrect the announcement is resent Four chances are given to respond correctly A 3 cr sequence will cause the Model 820 to hang up When a correct response is received the Model 820 indicates it is ready to send data when requested with 820 Ready enter Model 820 Answering Procedure Step 1 Step 2 The modem informs the Model 820 that a connec tion has been requested that is the phone is ringing The Model 820 answers the phone Model 820 Technical Reference Manual Example 820 ATDT 1 555 1234 Enter Modem 10 Enter Modem 2 enter 820 ATA enter B 35 Step 3 The modem informs the Model 820 that a connec Modem 10 enter tion has been made The Model 820 modifies its baud rate to that of the connected modem If the con nection is unsuccessful the procedure is retried in 4 min Step 4 The Model 820 sends the following announcement 820 820A0123 001 0 enter where 0123 is the Model 820 s serial number 001 is the monitor number entered and 0 is a flag 1 Alarm 2 Exceedance 4 Low Memory More than one of these can be set at a time in which case x is the sum of all set flags Step 5 The Model 820 awaits a response code which should be 820A0123 11111111 enter where 0123 is the Model 820 s serial number and 11111111 is the Lock Combination parameter 28 which is required whether or not the Model 820 is currently locked If the response is incorrec
101. exceedance will be mea sured at the beginning Max The exceedance will be mea sured at the maximum 168 Rt EXCD Report No Yes Print exceedance report in real time 169 Rt INTV Report No Yes Print interval report in real time 170 Rt HIST Report No Yes Print history report in real time 8 20 Model 820 Technical Reference Manual 171 Rt RUN LOG No Yes Print run log history 172 Rt Daily Report No Yes Print daily report 173 Rt CAL Report No Yes Print cal report 206 Daily Save L s Yes No Enables L table for daily history Model 820 Technical Reference Manual CHAPTER Memory Usage Each of the Model 820 s History Functions use space out of a common memory The amount each record takes is based on the options selected In this chapter we will provide informa tion that will assist you to Determine the amount of storable data considering the given options Estimate memory usage by giving an example of a test reading and an associated chart to determine the memory needed to complete the reading Determine Storable Data The following tables indicate the amount of memory used for each type of record Exceedance Records Excd History Enable Yes Prm66 Options add bytes shown if enabled Bytes Basic Exceedance Record 32 Excd Time Hist Yes Prm 69 plus number of samples 129 bytes max Save full accumulator and Count in B
102. fferent dose readings To protect the measurement the OVERALL Dose settings parameters 48 50 may not be modified once the measure ment has started without a reset However OVERALL CRI TERION may be changed at any time aS _ The average RMS level in this reading is 68 2 dB slow average for the 12 minute and 14 9 second measurement period Parameter 51 Full Dose Period or Criterion Time applies to Cur rent Overall and LDL Model 820 Technical Reference Manual Taking a Measurement 5 9 If you wish to look at dose with different exchange and thresh old values LDL may be used by modifying the LDL settings parameters 52 54 Note that the run time for LDL and OVERALL is always the same A new measurement may be started at any time without effect ing the Overall Dose using the Current Dose settings by modi fying the CURRENT exchange rate and threshold settings An automatic reset occurs when CURRENT settings are modified creating a new CURRENT dose measurement based on data collected from that time on Before we continue with our present measurement take a min ute to examine the parameter values available all of which will effect the measurement The Current Exchange Rate parameter item 45 is quickly accessed by following the following steps Press 3555 Modify 4 and b then Enter The choices here are listed below Step 1 3dB 4dB 5dB 6dB The Current Threshold item
103. gation It is related to wavelength through the following equation Model 820 Technical Reference Manual where A is the wavelength c is the sound speed f is the frequency in Hz and is the radian frequency It has the dimensions of inverse length Yearly Average Sound Level YDNL Lyan The Day Night Average Sound Level for each day is averaged over the entire year It is calculated as follows 365 1 Lyan 10108 TON i l Ldn 10 Model 820 Technical Reference Manual C 19 Index A AC Clock output 8 2 5 dry gr tee Hs Accessories 1 12 EO IS AC DC Output 4 8 Koo MP EN B 5 American National Standards Conventions Institute see ANSI 1 5 formatting ette 1 3 ANSI 8 12 standards 11 3 Answering Procedure B 35 sound level rete C 3 Appendix A Customer Support Specifications 1 2 Appendix C D 8 18 2 7 setting parameters 7 14 de i B 28 B Data determine storable 9 Battery ioci se bita HI S qe ON T tutes 5 14 time 7 3 directions for checking voltage 2 10 Data Reading internal life of s reete 1 18 Chapter 5 5 Km 2 6 DA
104. h OVERLOAD Setting the Daily History Parameter Setting and Viewing Advanced Functions The Model 820 has a variety of advanced functions that allow for gathering and storing great amounts of data with any given measurement In this section you will learn how to access the parameters choose the proper settings and view some of the data collected Time History Model 820 Technical Reference Manual History Functions 7 1 Time History records include the rms integrated level and if selected Peak Unweighted Peak or L Parameters 80 87 allow you to select the period for the history and what data are to be saved Step 1 Turn the Model 820 on and access Time History parameters Press 29 The following screen item 80 Time history Enable appears Yes With this item set to the time history function is enabled Despite Model 8205 large mem ory ensure anticipated require ments do not exceed available memory Step 2 To enable the Time History press gt to Yes and Enter Step 3 Press v to item 81 History Resolution Normally all data is taken with 0 1 dB resolution 2 bytes level To 1 0 d B 0 1 dB save memory this option allows storage of history in 1 0 dB resolu tion Step 4 To change this setting press Modify gt Enter Step 5 access item 82 Hist Save Peak press v This option allows saving the weighted peak Peak unweighted No Peak UWPK Lmax
105. he Microphone to the Preamp You will then be ready to use the Model 820 for actual measurements as described later in Chapter 4 of this manual Unpacking and Inspection Your Model 820 has been shipped in protective packaging Please verify the package contents with the following list Accessories and Optional Equipment and retain the shipping containers for safe shipment at a future date Report any damage or shortage immediately to Larson Davis Inc at 801 375 0177 If you have not already done so please record at the beginning of this manual see the copyright page your instrument s serial number located on the label on the back of the Model 820 the microphone serial number located inside the microphone the preamp serial number and the purchase date You will be asked to give this information in any future communications you may have with Larson Davis Inc Accessories The Model 820 is delivered with the following standard accessories The standard Model 820 Precision Sound Level Meter including one of the 1 2 inch precision air condenser microphones in Table 1 1 Microphones for use with 820 on page 1 8 and Model 828 preamplifier Alkaline battery 9 volts GLR61 or NEDA ANSI 1604A A good quality alkaline cell should provide more than 16 hours of Model 820 operation Since most rechargeable cells have less capacity expect shorter use User manual 1 12 Getting Started Model 820 Techn
106. he following types A Weighting A filter that adjusts the levels of a frequency spec trum in the same way the human ear does when exposed to low lev els of sound This weighting is most often used for evaluation of environmental sounds See table below Model 820 Technical Reference Manual C 7 eq Level dB C 8 B Weighting A filter that adjusts the levels of a frequency spec trum in the same way the human ear does when exposed to higher levels of sound This weighting is seldom used See table below C Weighting A filter that adjusts the levels of a frequency spec trum in the same way the human ear does when exposed to high levels of sound This weighting is most often used for evaluation of equipment sounds See table below Flat Weighting A filter that does not adjust the levels of a fre quency spectrum It is usually an alternative selection for the fre quency weighting selection Center Frequencies Hz Weighting Network Frequency Response 1 3 Octave 1 Octave A B 20 50 4 24 2 6 2 25 44 7 20 4 4 4 31 5 31 5 39 4 17 1 3 0 40 34 6 14 2 2 0 50 30 2 11 6 1 3 63 63 26 2 9 3 0 8 80 22 5 7 4 0 5 100 19 1 5 6 0 3 125 125 16 1 4 2 0 2 160 13 4 3 0 0 1 200 10 9 2 0 0 250 250 8 6 1 3 0 315 6 6 0 8 0 400 4 8 0 5 0 500 500 3 2 0 3 0 630 1 9 0 1 0 800 0 8 0 0 1000 1000 0 0 0 1250 0
107. hese values press these keys together and The current measurement Lmin the following display will appear occurred on November 27 1996 at 9 21 A M Remember the Model 820 used military time to designate between A M and P M That L nin value was 51 5 min There are no other screens avail able from this display 5 6 Taking a Measurement Model 820 Technical Reference Manual PEAK UWPK The Model 820 also has a peak level detector Its values dur ing the measurement or when stopped are found by pressing the key Step 1 Access Peak values Press 0 Step 2 The second display available from this function is accessed by pressing gt key Unweighted Peak UWPK has two screens available as well and are accessed with the SHIFT and keys Model 820 Technical Reference Manual PEAK is a weighted value and rep resents a true Peak SPL from the on board Peak Detector In this example the PEAK is 116 2 dB and occurred at the time and date shown on the screen Parameter 63 sets the level above which the readings must go to be recorded by the Model 820 Parameter 63 controls the setting for this measurement Here the set ting is 74 dB C weighted and in this measurement was equal to or exceeded 46 times The unweighted Peak value is the unfiltered no A or C weighting signal from the Peak Detector Taking a Measurement 5 7 Step 1 Step 2 For the second screen
108. hile in setup Model 820 Technical Reference Manual Understanding the Model 820 Keypad Getting to Know Screen Symbols Symbols basic to the Model 820 are included below These are generally found to the right of the screen The Operating Mode Indicator upper right character indicates whether data is being accumulated or not and has the modes indicated by the first four examples The Keyboard Status Indicator displays which key functions are active The lower four modes are possible and appear in the lower right corner or the display Symbol Functionality S S S flashing upper case to lower case Model 820 is stabilizing upon warm up 10 45 sec or SETUP weighting 8s or bias voltage 30s change in stop mode Stop mode no data is being taken Run mode OV Overload These letters in succession occur alternately with the stick figure with 8 second intervals when an overload has occurred f flashing Indicates that the function keys Linin Dose etc are used for different pur pose in the current function Indicates that numeric key input mode is n active 2 8 Getting to Know Screen Symbols Model 820 Technical Reference Manual Symbol Functionality S l 2 SHIFT key active secondary function in Orange lettering S S If the Model 820 is still stabilizing upon r warm up and the R S Run button is pushed r will flash alternately with S U
109. hted peak exceedance level 64 Uwpk Excd Level 0 255 dB Unweighted peak exceedance level 65 Excd Hysteresis 0 9 This sets the amount once an exceedance occurs that the level must drop below the exceedance level before the Exceedance event ends and anew exceedance can occur Normally set this level to 2 or 3 dB This pre vents multiple exceedances for a sin gle event if the level flickers around the threshold Exceedance History 66 70 161 163 These parameters select and define what data are to be saved in memory during an exceedance No Prompt Entry Comment 66 Excd Enable No Yes Yes Exceedance report will be stored in memory when exceedance condi tions above are met 8 14 Model 820 Technical Reference Manual 67 Excd Exchange 3dB 4dB 5dB 6dB Used to calculate exceedance inte grated level Normally this is set to Leq 4dB gives L_DOD 5dB gives LOSHA 6dB gives 68 Ex Min Duration 0 255 Exceedance must last at least this many seconds to be logged 69 Excd Time Hist No Yes Exceedance time history is saved if set to Yes 70 Excd Hist Per 0 255 Exceedance time history sample period in 1 32 s Ten samples before and after the exceedances are nor mally stored up to a maximum of 255 samples 161 Timed EXCD Per mm ss Exceedance Time history is recorded from 10 samples before e
110. ical Reference Manual Soft carrying case belt pouch Larson Davis part CCS009 WS001 a3 1 2 inch windscreen Wind noise can adversely affect measurements Using the windscreen on the microphone reduces wind noise and protects the element from dust and bumps SWW SLM UTIL software Utility software package allowing data retrieval and trans lation of binary files generated by the Model 820 to ASCII File Format via RS 232 connection and is capable of editing and storing instrument setup parameter to the PC or loaded directly to sound level meter Optional Equipment The following optional equipment is also available Model 820 Technical Reference Manual ADP005 BNC to preamp thread adapter to input direct signal through preamp Includes equivalent capacitance and shorting connector for noise floor testing 12 Adapter for direct signal input to the Model 820 Must be used only with DC coupled sources 1200 ohms or less CBL033 Printer cable for direct printout to serial printer 6 feet CBL034 Connects Model 820 to un wired cable end 4 conductor shielded CBL035 Connects Model 820 and customer supplied external battery CBL040 Similar to INTO02 but allows one to daisy chain an additional Model 820 CBL042 AC DC output of the Model 820 to RCA BNC connectors CBL116 Connects Model 820 to a PC or a modem Pro Getting Started vides connection for external power adaptor such as PSAO17 o
111. ilor your report and select the printer type and Model 820 Technical Reference Manual Printing a Report 10 1 Step 3 Step 4 Step 5 10 2 options press 7 and the following screen will appear There are several options here which include HPJet HPLzr ASCII Epson IBM You can change the printer selection by pressing the key and then to the printer you will use and press Press key to next display item 89 dupli cated here as item 177 the beginning of the param eters that manage printouts Scroll through these parameters with the key and make your selections Press to access the appropriate choice and press Enter Items 89 113 allow you to select the reports which are to be printed and how the output data are to be configured Items 89 113 are copied sequen tially into items 177 201 for print ing tailored reports and may be edited directly for one printing and then they will revert to settings entered in parameters 89 113 For a complete list of Print Options see Chapter 8 page 21 Normal Printout Parameters Model 820 Technical Reference Manual Printing Reports Printing reports is easy as connecting your Model 820 to a printer and pressing a key Using the CBL033 serial printer cable connect your serial printer to the Model 820 at its bot tom port Let s look at the print options again Step 1 Turn the Model 820 on and press 8 The dis
112. inary Aux Cntl Reg bit value 16 Prm 210 Model 820 Technical Reference Manual Memory Usage 9 1 Interval Records Intv History Enable Yes Prm 72 Options add bytes shown if enabled Bytes Basic Interval Record 34 Intv Save Ln s Yes Prm 77 18 Intv Ln Table Aux Cntl Reg Bit Value 1 Prm 210 Daily Records Daily History Enable Yes Prm 88 Options add bytes shown if enabled Bytes Basic Daily Record Save Daily Ln s Yes Prm 206 Daily Ln Table Aux Cntl Reg Bit Value 1 Prm 210 Time History Records Time History Enable Yes Prm 80 Options Bytes Hist Resolution Prm 81 Hist Save Peak Prm 82 1 0dB No 0 1dB No 1 0dB Peak UwPk Max Wind 0 1dB Peak UwPk Max Wind Other Histories and Memory Usage Bytes Run Log History 20 bytes per record Calibration Log History 17 bytes per record Ram Setup Register 506 bytes per register REgisters 0 9 Bytes used per register stored 9 2 Determine Storable Data Model 820 Technical Reference Manual Estimating Memory Usage The easiest way to estimate the memory usage is to work on a time basis such as one day Consider the following Estimate how many Exceedances will occur in a normal day Calculate the number of Interval Time History Daily Run Log and Calibration Check records that will be performed in a day Basedon the options chosen cal
113. interval num ber and date INTV b gives duration and interval number INTV c gives SEL and Log INTV d gives min and max level and the number of times level went over RMS exceedance 1 INTV e gives peak and unweighted peak levels INTV f h gives statistical informa tion Model 820 Technical Reference Manual Setting and Viewing Advanced Functions 7 7 Step 10 Press amp to view the next or previous Interval respectively Exceedance Exceedance is defined as an acoustic event characterized by the sound level going above or exceeding a predetermined level An exceedance event requires the following to occur The SPL must be above the RMS EXCD LVL 1 parameter 61 or the weighted peak level must be above the PEAK EXCD LEVEL parameter 63 or the unweighted peak level must be above the UWPK EXCD LEVEL parameter 64 and must be true for longer than the minimum duration param eter 68 An exceedance count on the other hand is obtained whenever the level goes above RMS EXCD LVL 1 RMS EXCD LVL 2 PEAK EXCD LVEL and UWPK EXCD LEVEL and are indi cated on the printout respectively This count has nothing to do with duration but only indicates the number of times the level went above the various exceedance levels Exceedance Level parameters are used to define the noise threshold levels to be used when counting the number of Exceedance during a measurement The number of times the four level
114. iod Units 1 05 b Index Parameter Text Indexed parameter texts must be preceded by a semicolon and enclosed by brackets Indexed parameter texts must include the maximum number of characters including spaces which are indicated below with This command may be used with flag 2 of the query command which automatically encloses the parameter and required spaces in brackets Syntax Response S et item number indexed parameter text cr If Examples 59 24001 sets Baud Rate to 2400 S66 Yes sets Excd History Enable to Yes S84 _1 32s sets Hist Period Units to 1 32s 584 _1 0s sets Hist Period Units to 1 0s Model 820 Technical Reference Manual B 13 Character String Parameters To include leading spaces in a character string parameter pre cede the character string with a leading single quote or grave accent ASCII 9610 or 6016 Syntax Response S et item number character string cr If Example 52 ABC Acoustics sets Name to ABC Acoustics Template Parameters _ Date The month day and year are entered in that order and are sep arated by The display shows day month abbreviated and year in that order Syntax Response S et item_number mm dd yy cr If Example 822 05 23 89 sets Timer Run Date to 23May1989 Time
115. is stopped Here we will examine them while a measurement is being taken Step 1 Press display the greatest RMS SPL value since the beginning of the measurement Model 820 Technical Reference Manual unfiltered A16 C16 and Flat do not apply to the Model 820 F 20 means Flat plus 20 dB of level added W 20 means Weighted with 20 dB of level added Flat record all sound and C weighting simulates the human hearing at higher sound levels This selects the polarization volt age for the microphone Choose 28 or 200 V typically 200 V is cho sen for condenser type micro phones and 0 V for pre polarized microphones electret The highest RMS level occurred at 9 19 hrs and was 99 2 dBA on the given date Additional screens are available here recording the num ber of times the current reading has reached predetermined levels selected in parameters 61 62 Taking a Measurement 5 5 Step 2 Press the gt key and examine the second screen In this example parameter 61 was available in this series set to 55 dB and C weighted parameter 40 In this measure ment the RMS has topped this level times Step 3 Press the gt key to find the third screen The display shows that parameter 62 was set to 65 dB and is C weighted This measurement s topped this level 6 times The same key finds the Lmin values in conjunction with the SHIFT key Step 1 Examine t
116. ister for param eters and calibration data in EEPROM type memory that is not lost when all power is lost There are 10 RAM registers to store data SETUP Enables the setting of desired SETUP parameters each accessed by using the up and down arrow keys RCL The EEPROM register and the RAM register may be recalled by pressing the RCL key scrolling to the desired register and pressing ENTER Cancel Model 820 Technical Reference Manual Understanding the Model 820 Keypad 2 3 Functions R S This key starts and stops measurements RESET Restarts a measurement by erasing the values just measured This function can be used whether a measurement is in the run or stop mode Enter used to enter new parameters selected by the user SHIFT Allows access to the Orange letter functions on the keypad The Exceedance History 15 a record of noise events which exceed a programmed level for a time greater than a programmed minimum time period See parameters 66 70 LOCK The lock functions protect instrument data and configuration The level of security is configured in Setup MEM INTV INTV The Interval History provides a history of a number of measurement values for a moderate size time interval 1 minute to larger than 99 hours in one minute or greater steps It is programmed by parameters 72 79 MEM Memory use in percent bytes free and total byte available are provided as well
117. k is also shown The number of times the weighted peak level exceeds a programmed threshold is also counted and displayed b window UWPK The highest UnWeighted Peak Detector output level Lywpk The date and time of the occurrence of the is also shown The number of times the weighted peak level exceeds a programmed threshold is also counted and displayed b window Model 820 Technical Reference Manual Understanding the Model 820 Keypad 2 5 Keys Functions BATT LN Ly The L values represent the SPL exceeded n of the run time All values from 1 to 99 are available four or six of these are displayed at a time and can be changed even while running This key gives the percentage of power remaining in the 9 V battery or exter nal supply BATT b Gives Model 820 revision number and date TIME LEQ The Equivalent Level or Leq is a Time Weighted Average based on an exchange rate of 3dB true energy measure with no thresh old Time The date and time of last reset or mea surement start are available from the Time a display The current date and time are shown with the Time b display TIMER SEL SEL The Single Event Level or Sound Expo sure Level is an energy reading in decibels It is the TWA level plus 10 times the log of measurement time in seconds SEL b Gives exposure in Pa2H which is a linear representation of energy TIMER The ability to take a meas
118. l Level of current bin nnn n dB 2 Count of samples nnnnnc c or M for Kilo or Mega T3 n Percent of total nnn nn 5 1 Prints the accumulated timer for current level bin hhhhh mm ss s The table number is optional B 30 Model 820 Technical Reference Manual a Where n equals the table number 1 RMS 2 Peak amp 3 UnWeighted Peak Print Commands Brackets in the syntax indicate optional characters cr carriage return If line feed Syntax Response P rint print_no cr If Example If Example P9cr 1 sets all report enables in setup to No 177 ler 2 sets the Data report Run log and EXCD report enables short to 178 ler Yes and 192 ler 3 begins printing to the computer P100cr Syntax Description PO Standard Report Formatted from normal setup parameters Pl Data Report P2 Data amp Histograms P3 Short Full Report Histories with SHORT option 4 Long Full Report Histories with LONG option P9 All Report Enables Turned OFF P 100 Begin Printing a Report P 101 Begin Printing using RXD as Hardware Handshake flow control P 999 Abort Printing X 100 XMODEM Begin Printing same as P100 except through the XMODEM communication protocol X X transfer mode 2 in a row ASCII CAN or CHR 24 Model 820 Technical Reference Manual B 31 Err
119. lectrotechnical Commission IEC 651 and 804 1985 standards for Type 1 accuracy and offers following features Dynamic range of more than 100 dB for error free mea surements Impulse measuring range greater than 100 dB Standard microphone allows measurements typically between 30 and 140 db A in one range Optional micro phones allow measurements as low as 20 dB or as high as 190 dB A Mic bias is user selectable 0 28 and 200 V e Selectable A and C frequency weightings for hearing pro tector applications Multiple detectors provide simultaneous RMS and PEAK measurements Leq integrated level duration ranging from 1 second to 99 hours manually controlled Measures FAST SLOW Unweighted PEAK Weighted PEAK Impulse Leg Losna Dose Projected Dose TWA Sel L L six user defined L s Lap CNEL and more max min User selectable dose exchange rate criterion threshold and reference duration Measures and stores more than 40 000 different DOSE Model 820 Technical Reference Manual Features combinations in a single measurement Allows compari sons of different DOSE standards using the same data Complete data logging capabilities with 256 kB standard memory Passby event data such as time duration L integrated about 10 dB of the maximum Les SEL max Selectively logs Exceedance when signal level rises above a user set threshold for a time longer than
120. n frequencies of 250 Hz to 1 kHz Model 820 Technical Reference Manual Step 5 Press Modify then enter the SPL value of your cal ibrator if other than 114 0 including any correc tions for pressure etc Step 6 The next setup item allows entry of the calibrator serial number for record keeping purposes Press the x or 5 Modify 3 and 6 and Enter Press to change the serial number enter the correct numbers and press Enter Step 7 Seat microphone fully in the calibrator cavity If possible both units should be at the same tempera ture and stationary so that hand vibrations are not transmitted to the SLM Step 8 Press to exit calibration setup Then acti vate the calibrator by pressing the button on its side Step 9 Press the and on the Model 820 This display indicates the current sensitivity off set and will be blinking between two settings Refer to the specific instructions accompanying your calibrator for accomplishing this step Pressing the will check cali bration pressing the w will change it Model 820 Technical Reference Manual Calibrating the Model 820 3 3 Step 10 Pressing key will initiate a calibration change Do that now Step 11 To Reset the Model 820 for re calibration press SHIFT and 4 Step 12 Press Enter Reset is complete and the instrument will return to the calibration mode Step 13 To leave
121. nderstanding the Model 820 Screen The operating screen for the Model 820 has several fields which vary according to the keys pressed on the keypad The most pertinent information is generally at the top and cen ter to left and instructions are generally on the bottom center to left Several characters are consistent in their appearance We will now turn the Model 820 on and examine a variety of pos sible screens Turning On the Model 820 Step 1 Press to power the Model 820 and initiate a self test Three successive displays will appear while the meter stabilizes for 10 45 seconds The first dis play has copyright information and appears only 1 to 2 seconds Step 2 The next display automatically appears The second display shows the pro duction date and the serial number uniquely assigned to your Model 820 This message appears for only 1 or 2 seconds Model 820 Technical Reference Manual Understanding the Model 820 Screen 2 9 Step 3 The third screen automatically appears The third screen appears almost immediately showing the title information for the current or last reading and is programma ble by the operator At this point you can change the parameters and begin taking actual measurements Checking the Battery Voltage The Model 820 continuously monitors its battery voltage to ensure accurate measurements It has a battery life of about sixteen hours It will t
122. ndom incidence to mini mize the influence of orientation A microphone influences the sound being measured The micro phone measures very small forces low level sound can run about one billionth of a PSI Every measurement instrument changes the thing being measured and for very small forces that effect can be significant When sound impinges directly on a microphone the incident wave must be reflected since it cannot pass through the microphone This results in the extra force required to reflect the sound and a microphone output that is higher than would exist if the microphone were not there This is more important at high fre quencies and when the microphone is facing the sound source Rules 1 Do not use a microphone at frequencies higher than specified by the manufacturer to increase the frequency response choose smaller microphones 2 Choose a microphone for free field or random incidence to mini mize the influence of orientation Model 820 Technical Reference Manual Near Field Noise A microphone measures what is there from any direction Most measurements are intended to measure the sound level of a specific source but most microphones are not directional so they measure whatever is there regardless of source Rules 1 When making hand held measurements keep your body at right angles to the direction of the sound you are interested in and hold the meter as far from your body as possible Use a tripod whenever pos
123. nsure the exceedance report will be stored in memory when exceedance conditions 61 65 are met Used to calculate exceedance inte grated level and normally set at 3 dB Leg 4 dB gives Lpop 5 dB gives 6 dB gives Layg This parameter sets the minimum duration in seconds of exceedance records With this item set to Yes a time history is saved only during the time an exceedance event occurs The exceedance time history sam ple period is in 1 32 seconds Ten samples before and after the exceedance are normally stored up to a maximum of 255 samples Setting and Viewing Advanced Functions 7 9 Use the x key to scroll through the fields Use the Modify gt and keys to make any changes desired within each field End of Start of Exceedance Exceedance start Hysteresis Threshold Duration Figure 7 1 Exceedance diagram The diagram above is an example of an exceedance with markings of explanation It should be noted here that additional parameter settings have been added out of numerical sequence to satisfy additional needs found in the field These will now be explained 161 Timed EXCD Per mm ss 162 Excd Trigger Level PassBy 163 Excd Time Start Max 7 10 Setting and Viewing Advanced Functions Exceedance Time history is recorded from 10 samples before exceedance to 10 samples after this period Must be in Level Passby treated later S
124. nt errors because of their limited dynamic range pulse range and crest factor The Model 820 does not have these limitations Furthermore its internal firmware is designed to accommodate changing regulations and to overcome sound measurement problems While the Model 820 is the size of a dosimeter it is also a complete environmental noise monitor offering features which will ensure quality measurements for many years We invite you to read this manual to get the most out of your new Larson Davis sound level meter About This Manual This manual has 10 chapters and 3 appendices covering the following topics Model 820 Technical Reference Manual Introduction Chapter I Introduction Overview of this user manual and the Model 820 s functions and measurement capabili ties Chapter 2 Overview to Model 820 Understanding the keyboard and screen turning the instrument on and off and checking the battery voltage Chapter 3 Calibration Using a reference to calibrate the instrument and its importance Chapter 4 Quick Start Setting parameters using function keys and using numbers and other characters Chapter 5 Performing a Measurement Reading the Data taking a measurement and becoming familiar with the function keys Chapter 6 Timed Measurement Using the timer for unat tended readings setting additional parameters and using the password lock Chapter 7 History Functions Setting parameters for ex
125. nt microphone 2559 or 2560 may be pointed in any direction Measurement Ranges RMS Detector Dynamic Range gt 110 0 dB Primary Indicator Range gt 105 0 dB The instrument will have a different Noise Floor Lower Limit and Overload Level depending on the sensitivity of the micro phone used Some typical values for 2 different Larson Davis microphones are listed in the table below Max Level for A Weight C Weight Overload Pulses of Microphone Noise Floor Noise Floor papers Level L Crest Factor dBSPL dBSPL dBSPL eve 10 dBSPL 2541 17 5 16 5 23 5 130 0 133 0 112 0 2559 29 0 28 0 35 0 141 5 144 5 123 5 Model 820 Technical Reference Manual Measurement Ranges A 3 The data in the above table was obtained by electrically testing a number of instruments For all electrical tests the micro phone was replaced with an equivalent electrical impedance Larson Davis ADP005 microphone adapter Other Detectors Weighted Peak Detector 85 0 dB Unweighted Peak Detector 38 0 dB AC Output 88 0 dB DC Output 105 0 dB Reference Level The reference level is 114 0 dB SPL Frequency Weightings The available frequency weightings for the Models 820 are described in the table below Detector A Weight C Weight Flat Mid RMS 4 4 Weighted Peak 4 Unweighted Peak 4 4 AC Output 4 4 4 DC Output 4 NOTES 1 The RMS frequency weighting is s
126. od using the chosen Exchange Rate Factor Exposure to this sound level over the period would result in the same noise dose and the actual unsteady sound levels If the Model 820 Technical Reference Manual Glossary 1 Calibration Measurement Duration is the same as the Criterion Duration then Layg LrwA LC 1 410810 10 00 where the Measurement Duration specified time period is gt T and 4 is the Exchange Rate Factor Only sound levels above Threshold Level are included in the integral Standard ANSI 12 19 Adjustment of a sound or vibration measurement system so that it agrees with a reference sound or vibration source It should be done before each set of measurements Community Noise Equivalent Level CNEL Laen A rating of community noise exposure to all C 2 sources of sound that differentiates between daytime evening and nighttime noise exposure The equation for it is 1900 2200 2400 1 10 10 1 10 L 5 10 1 10 10 Lien 109810 gt 10 gt 10 10 10 0700 1900 2200 The continuous equivalent sound level is generally calculated on an hourly basis and is shown in the equation as L The levels for the hourly periods from midnight to 7 a m have 10 added to them to represent less tolerance for noise during sleeping hours The same occurs from 10 p m to midnight The levels for the hourly periods between 7 p m and 10 p m have 5 added to them to repre
127. of the measurement is given The Alarm can be set to begin a measurement at a designated time The here indicates the next measurement has not been chosen The current internal tem perature as measured by the Model 820 is shown in the lower portion of the screen Model 820 Technical Reference Manual Taking a Measurement 5 3 Step 8 The property controlling the final screen in this series is built into the Model 820 to conserve power Press key Now that you are more familiar with the information available in the displays above lets take a closer look at the parameters that affect these readings Step 1 access these parameters turn the Model 820 on by pressing Next press Modify 3 9 Or press and the following screen will appear Step 2 The Detector prompt has three possibilities indi cated above Press Modify gt to access desired set ting and Step 3 To set the Frequency Weighting press v to item 40 There are several possibilities here A16 C C16 The Model 820 has been pro grammed to save power whenever it can Each time input is made the internal timer will start at 100 and count downward If not pro grammed to do otherwise the Model 820 will turn itself off when this screen reaches 0 just over two minutes Pressing the key again will scroll loop you back to the SLM original screen Slow exponential avg
128. or Messages and Warnings The code listed is the number provided by R98 All error messages begin with CHR 7 ERROR Error Code Message 1 COUNT OVERFLOW 2 EXPONENTIAL OVERFLOW 3 RTX TASK SELECT ILLEGAL EXCHANGE RATE UNKNOWN INTERRUPT WATCHDOG RESET OPCODE ERROR All warning messages begin with CHR 7 WARNING Add 128 to these numbers to get the actual warning number Warning Code Message 28 Out of Memory 29 Battery Low 30 POWER FAILURE 31 DIVISION BY ZERO 32 Operand 1 Range 33 Operand 2 Range 34 DPC Format 35 Key Has No Effect 36 Stop Required 37 Key Has No Effect In VIEW 38 Parameter Entered Wrong 39 RESET ALL Required 40 Use ARROWS ON to Exit 41 Use NEXT PREV ENTER B 32 Model 820 Technical Reference Manual 142 Invalid Numeric Entry 143 OPEN 144 Already Open 145 No History Yet 146 At End of History 147 At Start of History 148 History Format Error 149 Unknown I O Command 150 T O Operand Invalid 151 Unable to Calibrate 152 EEPROM Write Error 153 Memory was Lost Data Reset 154 RECALL Not Found 155 Function
129. ower Off To unlock unit and send lock combination to unlock parameter with 5230 command where is the correct combination entered before locking M 12 Disconnect Modem M 1000 Non destructive memory test walking bit M 1001 Destructive memory test pattern test Read Variables Syntax Variable Description Response RI DEVTYPE Device manf and model String R2 Current Date and Time ddd ddmmmyyyy hh mm ss R3 STAT Status RUN PAUSE STOP RESET C RESET O LOCKED A short form of the status command is R3 1 which has a 5 character response The first is an 5 when stabilizing or a space when stable The second is the current mode S for Stopped R for Running for Paused for Calibrating for View mode O for stopped with overall data reset and for stopped with Current data set reset The third character is the Lock Status and is either an L or a U The fourth character is the Halt Line Status and is a 1 if high and a 0 if low The fifth or last character will be an a if an Alarm has been detected R4 _C SPL Current SPL nnn nn dB Model 820 Technical Reference Manual B 5 R5 _O RTIME OverAll Runtime hhhhh mm
130. play will begin to scroll through the various print options available Here are some of the screens You will notice that the scroll is quite rapid To slow it down so you can study the options use the a or v keys and the display will remain for five seconds before returning to automatic scroll This option allows you to access the printer setup status This option will return you to the Printout Parameters and will start with the printer type selection The v key will access item 89 of the Printout Parameters This option allows you to tailor your own report changing the set tings of parameter items 89 113 but imputting the entries in items 177 201 After the printout is com plete the values will revert back to factory settings Model 820 Technical Reference Manual Printing Reports 10 3 Step 2 key until you find the Exceedance History report screen The brackets contain the command that will produce the Exceedance Report i e EXCD Step 3 To generate an Exceedance Report press the key Assuming your reading has Exceedances the report will contain all recorded occurrences during the test period Real time Printing Another feature of the Model 820 is the ability to print out reports in real time These are called the real time printer parameters or Rt print parameters These parameters are listed in Chapter 8 and duplicated here
131. ple To enter the company name of Larson Davis in the first line follow these steps a To access the Name Display turn on the meter Press site Modify O2 Enter b Press to place the cursor at the beginning or use or gt to position the cursor c To clear the field if necessary press GHIFT twice and 4 key d The letter L is on S field Press SHIFT e The letter A is on the S field Press GHIFT again f The R S O keys are in the 2 field Press GHIFT twice to access the 2 field g To Clear the field press SHIFT twice to access the 2 chart and press the Clear key To replace a character with a Space press SHIFT twice to access the 2 field and press the Space key When the first line is completed press v to go to the next field the second line Press and select the appropriate chart by pressing SHIFT and the desired character key When the second line is complete press the v to go to the next field the third line and repeat the pro cess The fourth line is for the Measurement Title Press the v key Setting Parameters Using Numbers and Other Characters A 3 will appear for five seconds The letters from the 3 panel are available for entry The display in Step 1 above will appear If you change your mind about clearing the field hit to return to the original title Repeat a and b in Step 5 to return to this point Enter the L
132. press key Press SHIFT and and examine these values for the current reading The value for the UWPK is set in parameter 64 and is 85 dB This value was reached 30 times Ln L values are determined by parameters 55 60 and should be examined next in our current measurement Step 1 Access L by pressing the key and a screen Step 2 Press the 5 8 similar to the following will appear three key to access the second screen of Parameters 55 56 in this example were set to 5 and 10 respectively This screen shows their values in this measurement These indicate the sound pressure levels that were exceeded 5 and 10 of the mea surement duration Parameters 57 58 were set at the given values shown in the screen and their readings are apparent Press the key to see the third screen and the values recorded there Model 820 Technical Reference Manual Taking a Measurement L The average RMS level the Leg is displayed by pressing 15 Dose LDL DOSE the noise exposure may be calculated with three dif ferent sets of parameters Current LDL Log Data Logic Overall Parameters 45 54 are used with the calculation to arrive at the current dose from the current data and sets the exchange rate threshold level and criteria level for the current measurement These can be set differently from the overall in order to give di
133. pter 6 Chapter 7 Chapter 8 Ee 5 9 suem peteret tee D OPE 5 9 BATTERY iut Re c i Ra e thi 5 14 eo eee net re RE Ege P HR dh PERRA 5 14 Stopping the Measurement 5 15 Timed Measurement 6 1 Using the Timer for Unattended Readings sss 6 1 Using the Time Key Functions 1 4041120212 2 41 2 02 200600000000000000004000000 6 4 Setting the Password Lock to Protect 6 5 History Functions 7 1 Setting and Viewing Advanced Functions sse 7 1 Time History e tei te cte tn ity den tv p editi ee HR 7 1 Time History 7 3 Lg acces RERO UE A RUE TTG EN RII EES 7 4 Interval History RUE ROR UE ee Qs 7 5 Ex e edance e on ac ener ER rte HS e 7 8 Setting PassBy Functions eR ER TRE e 7 12 84541124 ete ep e P PD OUO 7 14 Setting the Daily History Parameter sss 7 14 Parameters 8 1 Parameter Key Access tit ca ete e e ie Pe Mae aa 8 1 Entering and Exiting the Setup Menu 8 1 Locating Paratnetets acento ERE EORR 8 2 Changing Parameters Enter Modify 8 3 Error MESSAGES vo ee co ege reete me vae ue eres 8 4 Learning to Store and Retrieve Setup Memory sss 8 4 Sto
134. r it is Prms t 5 The sound pressure is squared and multiplied by a exponential decay factor so that when the time of integration is near the current time t it is essentially undiminished For times older less than the current time the value is diminished and so becomes less important The rate at which older data are made less influential is expressed by the constant T The larger is it the slower the decay factor reduces and the slower the response of the system to rapid changes These are standardized into three values called Time Weighting See the values below Fixed Average The averaging process is over a fixed time period The equation for it is The sound pressure is squared and averaged over a fixed time period Unlike the moving average the sound pressures in all time intervals are equally weighted Sound Pressure Level SPL The logarithmic form of sound pressure It is also expressed by attachment of the word decibel to the number The logarithm is taken of the ratio of the actual sound pressure to a reference sound pressure which is 20 MicroPascals u Pa There are various descriptors attached to this level depending on how the actual sound pressure 15 processed in the meter Instantaneous The time varying reading on a meter face on in a meter output due to changes in the sound pressure The reading will depend on the time weighting applied The fundamental relationship between the two is logarithmic
135. r similar CCS002 Custom hard shell airtight watertight case 13 1 2 X 12 7 8 X 6 in EPS012 CCS002 weatherproof fiberglass case with cus tom cut foam interior and desiccant Sealed signal cable feed through Features lock hasp and may be chained through handle for security EPS013 Same as 5012 but with 8 Ah 12 Volt recharge able battery BAT004 Provides 1 week operation in normal conditions Includes CBL038 and battery charger 1 14 Getting Started Model 820 Technical Reference Manual EXCXXX Microphone extension cable length XXX feet Epson Printer e INT002 RS 232 cable level converter for data transfer to PC Requires 9 V battery or external AC power supply 5 001 included Note that external supply will also power the Model 820 e PSAO001 AC DC power adapter 115 Vac to 9 Vdc 50 60 Hz for use with 2 e PSA002 AC DC power adapter 220 Vac to 9Vdc 50 60 Hz for use with 2 e 820 OPTO1 Modification of the Model 820 for use in out door noise monitoring system using the Model PRM2101 Outdoor Preamplifier Includes addition of a second con nection to the 820 for control of the electrostatic actuator Also includes environmental testing and certification as follows Separate testing of 820 and PRM2101 in a com puter controlled environmental chamber Note Figure 1 4 or call Larson Davis for additional information on these and other accessories Model 820 Technical Reference Manu
136. r the 5 day ending date i e October 1 ie 00 MO OO and the following display will appear The five day block is now set Next we will set the time periods each day within the block Press the v to Run Time 1 and press start up time is 8 30 A M so press 0 8 83 0 and Enter and the display should look like this Press v to Stop Time 1 Press to enter the numbers 1 2 OO and then press Enter Step 10 Press the v to Run Time 2 Press to enter Model 820 Technical Reference Manual 08 00 our afternoon start time Press Enter Notice that military time is used 0 01 24 00 to avoid confusion Using the Timer for Unattended Readings Step 11 Press the v to Stop Time 2 Press to enter 16 CO and Enter Step 12 To check your Timer setup press This will return you to the main screen Press and the following screen should appear Step 13 If you press the gt key it will give you the morning time run If you press gt again it will give you the afternoon time run settings The Model 820 can now be turned off by pressing and placed in the test area Make sure to check the battery Chapter 2 or connect to external power Also con sider the safety of the instrument during the test period Finally verify that the current time and date are set correctly in the internal clock of the 820 The following section covers
137. red every 1 16 second Setting Item 83 to 0 is equivalent to set ting it to 256 This is for editing purposes only All history is stored regardless of this base level However only data above the base level are displayed This parameter controls the stored data which the preceding base level operates For example if this was set to Peak and the base level set to 100 dB only peaks 100 dB and above would be displayed The Model 820 provides an ampli tude distribution that can be printed If the resolution is not sat isfactory a different one may be selected and the amplitude distri bution re displayed or printed This is possible because all data is stored to the nearest 1 8 dB The Time History is used to view the data that was acquired with the settings discussed in the previous Setting and Viewing Advanced Functions 7 3 Step 1 access Time History press 9 and a screen sim ilar to the following will appear Step 2 Press key to sequence through the stored his tory data Log The Log key function is a Run Stop log It indicates how many times the measurement was started and stopped and at what time Once a measurement is in progress information can be exam ined as follows Step 1 Press and to access Log screens section In this example we are viewing the Leq and Peak data that was gathered during the his tory period This di
138. ring Setup scs Re TR et eR P S 8 5 R calling a Setup uidet noinen Sa eR in 8 6 Model 820 Setup 8 7 System 1 20 essences 8 7 Timer 21 27 U T toro ab e beo te eee 8 10 Lock OBI U E ere ege ea tees 8 10 Calibration 35 38 U C cci cst te ett ee e d s 8 11 Sound Level Meter 39 50 C8 11 Dose 5 D eee eat Ra RO SS E8 13 Ln Statistical Levels 55 60 8 13 Levels 61 65 V tee eto are Pre Piet 8 14 Exceedance History 66 70 161 163 8 14 Interval History 72 79 M Time History 80 87 eren eren H8 15 Print Options 89 112 s idet 8 18 Additional System Functions 152 154 161 8 19 Chapter 9 Memory Usage 9 1 Determine Storable Data ice pet RR ene Ie INTR 9 1 Estimating Memory Usage 9 3 Chapter 10 Printing a Report 10 1 Normal Printout 10 1 Printing Reports e RR Ben A ette 10 3 Real time Printing RNa EE 10 4 Appendix A Specifications A 1 ee eo ROO PEE ERROR NE EE PEN UU DRE ree A 2 Reference Direction ui nut ette A 2 Measurement Ranges cose e eae eerte X ERBEN RE A 3 RMS Detector 3 Other Detectors i rere te
139. rophone Electrical Impedance The Larson Davis 05 should be substituted for the 1 2 microphone when performing electrical tests on the Model 820 The Larson Davis ADP002 is used in place of a 1 4 microphone and the Larson Davis ADP006 is used in place of the 1 microphones Functions Measured e Leg eq max Lmin TWA SEL Dose Projected Dose Ln 1 99 Sound Exposure in pascal squared hours SE Pa H Time History Histograms Measurement Time Date Dura tion Taktmaximal 3 and 5 Ldn Exceedance Events Data Storage 820 256k byte Memory Typically 3 month memory retention with fresh battery Model 820 Technical Reference Manual Stabilization Time Memory protected during battery change 2 minutes mini mum Data Communications Serial interface for computer printer and modem commu nications Data Rate 19 200 bits per second Digital Display 2line 32 digit 7 segment LCD Full ASCII character set Fully annotated date displays parameter with units Digital Display Resolution e dB levels 0 1 dB Dose 0 0196 Elapsed Time 0 1 second Display Bargraph 120 dB range 1 dB resolution for SPL Real time Clock Calendar 24 hour clock hh mm ss 1 second resolution 100 year calendar 01JAN1999 A 10 Data Communications Model 820 Technical Reference Manual Automatic run stop timer with two alarms and four alarm times R
140. rs and the specific period is 4 hours and the average level during the 4 hours is 86 dB then 83 dB Day Night Average Sound Level DNL Lg A rating of community noise exposure to all sources of sound that differentiates between daytime and nighttime noise exposure The equation for it is 0700 2200 2400 1 10 10 L 10 1 10 10 Lan 1010810 gt 10 10 10 0000 0700 2200 Model 820 Technical Reference Manual C3 Decibel dB 4 The continuous equivalent sound level See definition is generally calculated on an hourly basis and is shown in the equation as L The values for the hourly periods from midnight to 7 a m have 10 added to them to represent less tolerance for noise during sleeping hours The same occurs from 10 p m to midnight They are energy summed and converted to an average noise exposure rating A logarithmic form of any measured physical quantity typically used in sound and vibration measurements Whenever the word level is used it implies this logarithmic form The relationship is relatively simple but the mathematics can become complex It is widely used and was developed so that the very wide range of any quantity could be represented more simply It is not possible to directly add or subtract physical quantities when expressed in deci bel form The word level is always attached to a physical quantity when it is expressed in decibels for example L represents the sound pressure
141. s You may also look at this while the instrument is running To do this follow this step Step 1 Press Exceedance which is now Passby and using the or keys scroll through the events Use the 9 gt keys to look at information about this event a EXCD a Time PassBy record and date b EXCD b Duration and record number of PassBy event c EXCD c SEL and L of PassBy event d EXCD d Max RMS level and Symmetry of PassBy record e EXCD e Peak PassBy level and UWPK of PassBy record Model 820 Technical Reference Manual If PSBY appears in the screen it means you are in the Max PassBy data screen SHIFT M to get the Exceedance PassBy screen Five screens are available here by using the key giving time and date of the occurrence duration and Leq comparisons Symmetry when used in PassBy mode is an indication of where Occurrence Time or Max Level occurs in the event To clarify 25 symmetry would indicate Max Level happened 1 4 of the way into the event in linear time 50 would suggest that the Occur rence Time happened half way into the event and so forth Setting and Viewing Advanced Functions 7 13 Step 2 examine the Maximum PassBy of all those col lected press GHIFT and the 4 key Use and gt keys to access the following data windows PSBY a Time and Date of maximum PassBy PSBY b Duration of maximum PassBy PSBY c
142. s were exceeded will be given in the data report To find the Exceedance parameters items 61 65 turn the Model 820 on and follow these steps Step 1 Press the Notice the available settings 0 to 255 dB for items 61 64 61 RMS Excd Lvl 1 First RMS detector exceedance level e 62 RMS Excd Lvl 2 Set above Level 1 63 Peak Excd Level Weighted peak exceedance level 7 8 Setting and Viewing Advanced Functions Model 820 Technical Reference Manual 64 Uwpk Excd Level Unweighted peak exceedance level 65 Excd Hysteresis 0 9 The Exceedance History parameters items 66 70 allow you to select and define what data are to be saved in memory dur ing an exceedance Each exceedance indicates the time it started durations sym metry Leg SEL Limax Peak and Time History if desired Step 1 Press and to access item 66 from the pre vious field or press 5 Modify 6 6 and Enter Here is a brief explanation of each parameter 66 Excd Enable Yes No 67 Excd Exchange 3dB 4dB 5dB 6dB 68 Ex Min Duration 0 255 69 Excd Time Hist Yes No 70 Excd Hist Per n 32 0 255 Model 820 Technical Reference Manual After an exceedance the level must drop this amount below the exceedance threshold before a new exceedance is logged This pre vents multiple exceedance for a single event if level fluctuates about the threshold Yes would i
143. see Chapter 4 If there is an angle bracket gt then the entry field is too big to fit the screen and will scroll with the key For complete coverage of numeri cal and alpha entry see chapter 4 8 3 Step 3 Confirm any change with Enter Step 4 Cancel any change by pressing before Enter Parameters whose value is selected from a few possible choices are displayed with the current setting inside square brackets To make a selection Step 1 Press and then the 4 and gt keys Step 2 Confirm change with Enter Step 3 Cancel change by pressing before Enter Error Messages Entry errors will be noted by a warning message For example Verify the correct entry format Learning to Store and Retrieve Setup Memory The current setup parameters can be stored internally in two ways for later recall Intwo RAM random access memory registers none EEPROM register electronically erasable program 8 4 Model 820 Technical Reference Manual mable read only memory Setups stored in RAM occupy the same memory as the data 256 KB They may be lost if battery power is removed for more than a few minutes One set of parameters at a time can be stored in the EEPROM Parameters in the EEPROM regis ter are secure even if the batteries are disconnected since the EEPROM does not require bias voltage to maintain its state A minimum of 5 000 STORE operations are possible with the
144. sible 2 Measure the influence of other sources by measuring the back ground sound level without the source of interest You may have to correct for the background There are two types of near fields the acoustic near field and the geometric near field Acoustic Near Field The distance from a source of sound is less than an acoustic wavelength In the near field the effect of the type of sound source is significant Since the wavelength varies with frequency See the definition of Wavelength the distance will vary with frequency The most common example of a near field is driving an automobile with an open window As you move your ear to the plane of the window the sound pressure level builds up rap idly wind noise since most of the pressure changes are to move the air and very little of it compresses the air to create sound Per sons not far way can hardly hear what you hear The acoustic near field is characterized by pressures that do not create sound that can be measured in the far field Therefore measurements made here are not useful in predicting the sound levels far way or the sound power of the source Geometric Near Field The distance from a source of sound is less than the largest dimension of the sound source In the near field effect of source geometry is significant Sound sources often have a variety of specific sources within them such as exhaust and intake noise When in the near field the sound of a weaker but
145. sound level meter with a simple user interface Model 820 Technical Reference Manual Model 820 Components 1 7 As can be seen the standard Model 820 includes the following Model 828 is a 5 1 2 inch precision preamplifier using a standard 5 pin SwitchCraft connector and may be extended up to 20 feet with EXCXXX microphone cable The preamplifier is removed by depressing the small black latch button with a fingertip while gently pulling it away from the mating connector A two line 32 character high contrast LCD display One of the 1 2 inch precision air condenser microphones in Table 1 1 Microphones for use with 820 on page 1 8 The microphones are rugged and reliable but should be kept in their protective case when not in use Avoid unnec essary shock Although an Larson Davis microphone can usually survive being dropped it is a delicate precise transducer that should be handled with care Sensitivity Microphone Type mV Pa Bias 2540 Free field 14 5 Voltage Required 2541 377B41 Free field 44 5 Voltage Required 377B02 Free field 50 0 Prepolarized 377A20 Random 50 0 Prepolarized 2559 Random 12 9 Voltage Required 2560 377A60 Random 45 2 Voltage Required 1 8 Table 1 1 Microphones for use with 820 Model 820 Components Keep clean and protect from con densing moisture and water The microphone 5 ultra thin diaphragm is covered by a protective grid which should not
146. splay contains History information about the measure ment It was started by a key stroke Press the key to view other readings This screen gives you information about the most current readings This measurement was started by a key stroke If it had been started by preset alarm Key would have been replaced with 7 4 Setting and Viewing Advanced Functions Model 820 Technical Reference Manual Step 2 View the start and stop times and date by pressing the gt key Step 3 back to LOG a by pressing key Toggle through the record logs by pressing Step 4 The and v keys may be used to look at addi tional records Press the to look at associated dates and times Interval History The nterval History Parameters allow you to select and define the interval size and determine what data are to be saved Each interval gives you Leg SEL Min Max Peak UWPK Exceedance count and if you turn this feature L s Listed below is each parameter and a brief explanation of its function Step 1 access the History parameters press 0 You may also use numeric values i e Modify 7 2 Enter The choices are Yes No Step 2 Press v to access the next parameter 73 Intv Exchange Rate for these choices 3dB 4dB 5dB 6dB Model 820 Technical Reference Manual The Log information indicates that the measur
147. t the announcement is resent Four chances are given to respond correctly A 3 sequence will cause the Model 820 to hang up Step 6 When acorrect response is received the Model 820 indicates it is ready to send data when requested with 820 Ready enter B 36 Model 820 Technical Reference Manual APPENDIX Glossary This appendix contains technical definitions of key acoustical and vibration terms commonly used with Larson Davis instruments The reader is referred to American National Standards Institute docu ment 51 1 1994 for additional definitions Specific use of the terms defined are in the main body of the text Allowed Exposure Time T It is the allowed time of exposure to sound of a constant A weighted sound level given a chosen Criterion Level Criterion Duration and Exchange Rate The equation for it is e P Uo where L is the Criterion Level T is the Criterion Duration Q is the Exchange Rate is the Exchange Rate Factor and is the Average Sound Level Example If L 90 T 8 Q 3 and 95 then tr 8 B 8 1009590710 565 9073 5 656 5 hours and 39 minutes This means that if a person is in this area for 5 hours and 39 min utes he will have accumulated a Noise Dose of 100 Standard ANSI 12 19 Average Sound Level It is the logarithmic average of the sound during a Measurement Duration specific time peri
148. t Base 0 255 dB This is for editing purposes only All history is stored regardless of this base level However only noise data above the base level are displayed on the screen 86 Hist Base Mode Off RMS Peak Type of noise data used by the base mode 87 Hist Resolution 1 8 1 2 1 0 2 0 5 0 10 Selects the interval in dB of the over all time level amplitude distribution 88 Daily Enable No Yes Yes to store daily data such as Lan CNEL Leq and background level This option provides the storage of 24 hourly noise levels for each one of these quantities when interval dura tion is 1 hour and Intv Time Sync Yes Model 820 Technical Reference Manual Print Options 89 112 These parameters allow for tailored reports of LDL Model 820 data during or after the measurement They can be accessed from outside the SETUP by pressing then 7 for printer type and options Refer to section on printouts for samples of information found on each printout No Prompt Entry Comment 89 Prn Data Report No Yes Prints quick data report 90 R S and Cal Log No Yes Prints Run Stop and calibration log report 91 Setup Report No Yes Prints list of current setup parameters 92 RMS Histogram No Yes Prints histogram of overall rms levels 93 Lowest Level 0 255 RMS Histogram lowest printed level 94 Highest Level
149. t Entry Comment 51 Full Dose Hours 0 99 This is normally set to 8 for an 8 hour workday It is used with the criterion level to determine a 100 projected dose 52 LDL Exchange 3dB 4dB 5dB 6dB Use LDL function to reevaluate stored data with new dose parameters 53 LDL Threshold 0 255 dB 54 LDL Criterion 0 255 dB Statistical Levels 55 60 Lan is the rms noise level which was exceeded nn of the time The L s are computed from the overall level distribution histogram or each interval s level histogram see item 77 The measured and displayed L may be changed during the mea surement The six nn are automatically listed in increasing order No Prompt Entry Comment 55 Lyn 1 Percent 0 to 99 56 Lin 2 Percent 0 to 99 57 Lin 3 Percent 0 to 99 58 Lun 4 Percent 0 to 99 59 Lin 5 Percent 0 to 99 60 Lin 6 Percent 0 to 99 Model 820 Technical Reference Manual Exceedance Levels 61 65 These parameters define noise threshold levels to be used when counting the number of exceedances during a measure ment viewed in MAX b and c displays for rms PEAK b UWPK b for peak exceedance and triggering the exceedance history see parameter 66 No Prompt Entry Comment 61 RMS Excd Lvl 1 0 255 dB First rms detector exceedance level 62 RMS Excd Lvl 2 0 255 dB Set above Level 1 63 Peak Excd Level 0 255 dB Weig
150. t screen Step 3 The third screen gives additional information Press the M key to examine this screen Stopping the Measurement Press to stop the measurement The stick figure will return to the resting position To view any of the previous mea surement data simply press the appropriate key and the infor mation will appear Total Exceedances were 27 total Intervals were 3 and IDaily Histo ries This display indicates there are 8 Histories in memory 3 Logs and 0 Calibrations Hs is the number of time history samples Lg is the number of RUN STOPs made and CL is the number of calibration check records Model 820 Technical Reference Manual Stopping the Measurement 5 15 CHAPTER Timed Measurement The ability to take a measurement at a specific time and date is one of the unique qualities of the Model 820 This feature allows you to take unattended measurements Accessed through the TIMER key this flexible system has modes to per mit one or two measurements a day between two dates or a single block measurement from a start date and time to a stop date and time In this chapter we will discuss Using the Timer for Unattended Readings Using the Time Key Functions Setting the Password Lock to Protect Settings Using the Timer for Unattended Readings Examine the capabilities by looking at the parameter y 5 fields Step 1 Turn the Model 820 on press 8
151. tart This setting will begin the exceedance measurement as it occurs Max This setting will register the measurement at the Exceedance maximum point Model 820 Technical Reference Manual Occurrence Time Tstart if set to Start Occurrence Time Tmax if set to Max max start t syrnimetry duration Lmax Must be gt rms Level 1 Only events that are longer than the minimum duration set and having Lmax greater than the RMS Exceedance Level 1 parameter 61 will be recorded It is also important to set the Excd Time History Period to 0 5 or 1 second by entering a 16 or 32 for parameter 70 since the exceedance time history buf fer is used to create this function The max duration of a passby event is 128 samples which is 64 or 128 seconds depending on whether 16 or 30 is used in parameter 70 To examine Exceedance data collected follow these steps Step 1 Press The following screen appears with some variation Five screens are available Time and Date and the Exceedance number as seen in the screen to the left Duration Leq compari sons Linge Symmetry Peak and UWPK Model 820 Technical Reference Manual Setting and Viewing Advanced Functions 7 M Step 2 Press M key to access the five screens available in the EXCD mode including Duration Leg los Pk UWPK Step 3 To examine the properties of each exceedance record use the 4 or keys to see screens a e Step 4 Press th
152. the Daily Noise History printout or downloaded to a computer Model 820 Technical Reference Manual Setting the Daily History Parameter 7 15 CHAPTER Parameters As we have seen in previous chapters the Model 820 owes its versatility in great part to a flexible setup More than 160 parameters and options can be selected to tailor the Model 820 to any measurement Four preprogrammed setups for standard applications are in memory One may use these as blueprints for modifications It is also possible to store up to 11 other set ups in memory for later recall Along with downloadable set ups from software this truly makes the Model 820 a myriad of instruments in one In this chapter we will review the following Parameter access keys Modify Enter Cancel Learn to store and retrieve complete setups from the vari ous memory registers List all parameters with short explanation Parameter Key Access Review Entering and Exiting the Setup Menu Some setup items may be changed while the Model 820 is run ning but parameters influencing data integrity require a mem ory Reset ALL Step 1 Enter the setup by pressing The following will Model 820 Technical Reference Manual Parameters 8 1 appear Step 2 To exit back to the main screen press Step 3 Return to the setup menu Press Locating Parameters When in the setup menu the arrow keys allow movement from one parameter
153. the appropriate cabling such as the CBL040 and each may be controlled individually Each is given a unique address parameter or item 10 The addresses are sent as a sin gle byte ranging in value from 129 to 255 representing address 1 to 127 respectively address plus 128 Whenever an address byte is received only the corresponding instrument is enabled to receive commands Baud rate Serial Port address and handshaking protocol are selected using parameters 9 10 and 12 Unless using addressing set the address to 0 The following instruments are compatible on a net work Models 712 720 812 820 870 and 100 Future instru ments may also be compatible with this network B 2 Model 820 Technical Reference Manual A broadcast command can be sent By sending an address of zero CHR 128 all units on the chain will become addressed and accept the commands that follow Only the device with an address of will respond to the commands if data transfer is required This will allow all units to be started at the same moment or to have the same parameter sent to all devices with one command i e set all clocks to the same time These devices cannot be just paralleled together That would short outputs together and damage the instruments Use the designated cables Commands The commands are a series of ASCII characters with an alpha command and one or two numeric operands followed by a charge return ASCII
154. the calibration mode press Cancel 3 4 Calibrating the Model 820 In this screen an error message initially prompted for a reset see step 12 to reset The difference between the current and the last calibration is 0 dB If the level is not stable enough for proper cali bration the Model 820 will exit the calibration mode without chang ing its calibration level The c indicates the instrument is cali brating The Model 820 will wait until the reading is stable indicator is SsSsSs then adjust the offset for the proper reading CcCcCc improper calibration offset for instance something greater than 34 0 dB may indicate that the cal ibration tone was shut off before calibration was completed or that polarization was not properly set You may repeat the previous steps or perform a Cal check The display will ask if you want to Reset ALL Data You do Model 820 Technical Reference Manual CHAPTER Quick Start Before running a simple measurement it is important to set a few parameters to meet your needs and become familiar with related functions In this chapter we will discuss these items Setting parameters using and Using numbers and other characters Setting Time Date and Day parameters Setting Parameters Using Function Keys The Parameter fields can be accessed in several ways Byentering numbers assigned to each parameter the num bers are located above the keys on
155. the keypad and are dis cussed later in the chapter By scrolling up or down using the or keys Byusing any white or Orange function keys Follow these steps to access the parameters using numeric val ues Step 1 With the Model 820 on press and the follow ing screen appears Model 820 Technical Reference Manual Quick Start 4 1 Step 2 Step 3 Step 4 4 2 A complete list of parameters and their assigned numbers is found in chapter 8 You have already vis ited parameter 43 Microphone Polarization and found it preset to 200 To access parameters using numeric values press access the Current Time press 0 and then 6 The number 6 is assigned to the Current Time parameter Press to prepare the screen for changes in the Current Time Notice the flashing f changes to n Notice that the flashing f has been replaced by a flashing n indicating the numeric key access The flashing parenthesis indicate this field is ready to receive numeric input Entering 0 before the new num ber will remove any prior parame ter settings The third way to access Current Time parameter press GHIFT GM Remember press to change or correct the field and press Enter Setting Parameters Using Function Keys Model 820 Technical Reference Manual Step 5 Using numeric keys make changes and press Enter or if the time is correct just press Enter
156. there Step 1 Press the key where two screens are available Press gt key to access the second screen LDL readings are displayed on four screens We will visit three of these screens using the following steps Step 1 Press the GHIFT and keys 5 12 Taking a Measurement The measurement ran for nearly four hours and the dose was 0 28 The Projected Dose extrapolates the eight hour dose from dose A which is the current measured dose Notice in the reading the LDL Threshold is set at 80 parameter 49 The Overall Exchange Rate is set at 3 dB parameter 48 The Overall Criterion has been set at 90 parameter 50 Any of these 3 parameters can be modified and a new dose projected dose Leq and SEL will be computed Model 820 Technical Reference Manual Step 2 Press key to check the LDL d screen PROJ DOSE that is calculated based on the current LDL settings Lan readings are displayed on two screens Step 3 Access Lg by pressing GHIFT Two screens are available using the key Ldn is the noise descriptor that applies a 10 dB weighting factor between the hours of 10 00 PM and 7 00 AM when calculating the Time Weighted average CNEL adds an additional 5 dB between the hours of 7 00 PM and 10 00 PM Ex in the second screen takes all exceedance records and aver ages them together BkGnd is the over
157. this device has a voltage applied across the diaphragm from an internal source Electret A microphone that uses the motion of a thin diaphragm caused by the sound to change the capacitance of an electrical cir cuit and thereby to create a signal The voltage across the dia phragm is caused by the charge embedded in the electret material so no internal source is needed Microphone Uses The frequency response of microphones can be adjusted to be used in specific applications Among those used are Frontal incidence Free Field The microphone has been adjusted to have an essentially flat frequency response when in a space rela tively free of reflections and when pointed at the source of the sound Random incidence The microphone has been adjusted to have an essentially flat frequency response for sound waves impinging on the microphone from all directions Pressure The microphone has not been adjusted to have an essen tially flat frequency response for sound waves impinging on the microphone from all directions What a microphone measures 4 microphone detects more than just sound The motion of a microphone diaphragm is in Microphone Guidelines cont response to a force acting on it The force can be caused by a number of sources only one of which are we interested sound Non sound forces are 1 direct physical contact such as that with a finger or a Model 820 Technical Reference Manual C 9 C 10 raindrop 2 those ca
158. tion on set setup and press SHIFT to lock ting the Lock parameters see chapter 6 Step 2 To unlock press SHIFT then Modify and enter the password No Prompt Entry Comment 8 10 Model 820 Technical Reference Manual 28 Lock Password 8 characters Enter your password 29 Lock R S Key No Yes Lock mode change 30 Lock Setup No Yes 31 Lock Function No Yes 32 Lock Reset No RES ALL Curt All 33 Lock ON Key No Yes 34 Lock I O No Yes Calibration 35 38 No Prompt Entry Comment 35 CAL Level 114 00 Enter the sound pressure level of your 0 255 dB calibrator 36 Calibrator S N to 8 char Calibrator serial no will be printed 37 Auto Cal Mode No Yes unused 38 Auto Cal Time 00 00 hh mm Sound Level Meter 39 50 These parameters define the sound level meter characteristics Most changes will require a SHIFT if memory holds pre vious data Allows automatic daily calibration check with LDL electrostatic actuator available at later date No Prompt Entry Model 820 Technical Reference Manual Comment 8 11 39 Detector Slow Fast Impl Slow exponential avg 1 second con stant Fast exponential avg 1 8 second con stant Impl impulse response 40 Frequency Weighting A A16 C C16 and weightings meet Type 1 spec ifications Not
159. tory Variables D1 D102 sse B 28 R n Log Variables iion nuage eite ee ein B 29 Calibration History Variables sese B 29 Time History 1 22 2 2 4 844441 0000000 000000000000000000040000000000004 B 29 Histogram Table B 30 Print Comimn rids un enne RR E B 31 Error Messages and Warnings 12 2 40200040000400000 0 00000000000000000000004 B 32 Modem Control e ce He Ub HE de b B 34 Modem Mode 154 c cssc eee h B 34 Dial Out Mode 155 orte RE ERAT REN B 34 Monitor oed e e Re Ere EP ERE CIPUE B 34 820 Phone Dialing B 35 Model 820 Answering 4 B 35 Appendix C Glossary C 1 Introduction Welcome to the Larson Davis Model 820 Your new hand held Model 820 from Larson Davis is a combination 1 preci sion integrating sound level meter and a statistical data logger that exceeds all worldwide accuracy requirements for the mea surement of noise The Model 820 measures sound with the ease of operation of a point and shoot sound level meter The latest advances in surface mount technology air condenser microphones and internal firmware have been combined in rugged lightweight yet extremely versatile unit Many sound level meters in the market can create significant measureme
160. ulated by dividing the actual time of exposure by the allowed time of expo sure The allowed time of exposure is determined by the Criterion Duration and by the sound level the higher the level the shorter the allowed time The sound levels must be measured with A fre quency weighting and slow exponential time weighting See Pro jected Noise Dose L L 10 T 1007 D 1007 T 1 where is the Measurement Duration is the Allowed Expo sure Time Standard ANSI 12 19 See Sound Exposure The Average Sound Level calculated in accordance with the Occu pational Safety and Health Administration Exchange Rate and Threshold Level Model 820 Technical Reference Manual Preamplifier Projected Noise Dose A part of the sound level meter that matches a particular model of microphone to the meter It must be chosen in conjunction with a microphone and a cable that connects them It is the Noise Dose expected if the current rate of noise exposure continues for the full Criterion Duration period Single Event Noise Exposure Level SENEL L 4x The total sound energy over a specific period It Sound Sound Exposure SE is a special form of the Sound Exposure Level where the time period is defined as the start and end times of a noise event such as an aircraft or automobile passby The rapid oscillatory compressional changes in a medium solid liquid or gas that propagate to distant points
161. un time Clock 0 1 second resolution Format hhhhh mm ss s Maximum gt 4 years Standards Met e ANSISI 4 1983 1 e ANSI S1 25 199 1 651 1 804 Type 1 Directive 86 188 EEC Directive IEC TC 29 CE Information The Model 820 SLM complies with European Community EMC Directive 2004 108 EC and also the Low Voltage Safety Directive 2006 95 EC by meeting the following standards EC61326 1 2005 Electrical equipment for measurement control and laboratory use EMC requirements IEC61000 4 2 2008 Electrostatic discharge ESD immunity 4kV contact discharges and 8 kV air discharges Model 820 Technical Reference Manual Run time Clock 11 EC61000 4 3 2006 Radiated radio frequency electromagnetic field immunity 26 MHz to 1 GHz at 10 V m 1 4 GHz to 2 GHzat 3 V m 2 0 GHz to 2 7 GHz at 1 V m with 1 kHz 80 AM EC61000 4 4 2004 Electrical fast transient EFT burst immunity 2 kV 5 50 ns 5 kHz EC61000 4 6 2008 Immunity to RF conducted line disturbances 10 V 1 kHz 80 AM from 150 kHz to 80 MHz EC61000 4 8 2001 Power frequency magnetic field immunity 80 50 60 Hz CISPR 11 2009 Industrial scientific and medical ISM radio frequency equipment Elec tromagnetic disturbance characteristics Limits and methods of measuremen t Class B e JEC61010 1 2001 Safety requirements for electrical equipment for measurement control and
162. urement Timed 6 noe 6 1 8 5 estimating 9 3 KOY 2 4 5 14 Setup 8 4 store and retrieve 8 4 usage Chapter 9 9 1 Memory Usage Chapter 9 1 2 Messages error messages and warnings B 32 Microphone 1 5 connecting 1 18 guidelines C 9 reference number 1 12 what it measures C 9 Microphone Extension Cables specifications A 7 Microphones CapacitOf 2 9 electrit 9 6662 E 9 commands seen B 4 2 1 2 9 Model 820 1 12 block diagram 1 10 Calibration 1 2 3 1 Components 1 7 1 5 1 2 Glossary App 1 History Functions 1 2 amp 1 2 Memory 1 2 9 1
163. urement at a specific time and date is available thus per mitting unattended measurements i e or two measurements day between two dates or a single block measurement from a start date and time to a stop date and time 2 6 Understanding the Model 820 Keypad Model 820 Technical Reference Manual Functions T A Time Weighted Average SPL TWA and the German Takt Maximal Levels TAKT are available through the T A key The first display a shows the Overall TWA and Run Time LDN The LDN is a TWA with a 10dB pen alty added to the levels measured from 10 pm to 7 am It is used to assess correlate or pre dict annoyance to noise in residential area noise at night 1s generally less tolerated than noise in daytime hours CNEL is also shown LDN b Shows the average levels of the exceedances and the average levels Bk Gnd of energy not contained in exceedances DOSE The Dose and Projected Dose sound exposure percentages are displayed in these screens Parameters 48 51 control the Dose measurement LDL Logged Dated Logic allows the user to recalculate TWA SEL DOSE and Projected Dose using new Exchange Rate Threshold and Criterion parameters during or after a measurement Arrows Up Down Left and Right arrows are used to change fields to modify information within a given field and can be used in con junction with other keys to allow other func tions Modify Prepares the field for changes w
164. urn off automatically when the voltage falls below 5 7 volts Therefore you should verify that the remaining battery capacity is sufficient before you make an especially critical or lengthy measurement Checking the Battery Voltage This screen will remain until the user inputs other commands The flashing uppercase S indicates system initiation and will continue 10 45 seconds When the system initiation is com plete a stick figure in the upper right corner of the display will appear seated indicating the Model 820 is in STOP mode Do not press the key during a measurement since it will pause the measurement while pressed Model 820 Technical Reference Manual Step 1 manually check battery voltage simply press the SHIFT keys Information similar to the follow ing will display Turning Off the Model 820 To turn off the Model 820 simply press SHIFT key Remember pushing a button can produce small low level noises which can affect your readings In addition the Model 820 momen tarily pauses the current measure ment whenever a key is pressed in order to interpret the keyboard event Therefore where possible do not press the key during a valid event you wish to measure The first screen a displays the percentage of power left in the bat tery an internal power source INT or indicates external power is being used EXTV The second screen b gives revi sion number
165. used by the movement of air over the dia phragm such as environmental wind or blowing 3 those caused by vibration of the microphone housing and 4 those caused by strong electrostatic fields Rules 1 Do not permit any solid or liquid to touch the microphone dia phragm Keep a protective grid over the diaphragm 2 Do not blow on a microphone and use a wind screen over the microphone to reduce the effect of wind noise 3 Mount microphones so their body is not subject to vibration par ticularly in direction at right angles to the plane of the diaphragm 4 Keep microphones away from strong electrical fields A microphone measures forces not pressures We would like the microphone to measure sound pressure force per unit area instead of sound force If the pressure is applied uniformly over the micro phone diaphragm a simple constant the diaphragm area relates the two but if the pressure varies across the diaphragm the rela tionship is more complex For example if a negative pressure is applied on one half the diaphragm and an equal positive pressure is applied to the other half the net force is zero and essentially no motion of the diaphragm occurs This occurs at high frequencies and for specific orientations of the microphone Rules 1 Do not use a microphone at frequencies higher than specified by the manufacturer to increase the frequency response choose smaller microphones 2 Choose a microphone for free field or ra
166. vel SPL Lp 15 unweighted C 16 weighted C 17 yearly average level YDNL Lydn C 19 Sound Event Level see SEL 2 6 Sound Level threshold Lt C 17 Sound Level Meter SIM 8 11 Sound C 17 17 Sound Pressure Level see Sound C 15 Sound C 17 Specifications 1 2 Index frequency weightings A 4 microphone extension cables A 7 reference direction A 2 reference A 4 7 Laa oe RA e eere erre A 2 Spectrum 17 Standards 11 Status COMMAN Gs decet eee eee B 5 Store determine strorable data 9 1 Symbol flashing f 2 8 n imeric secedere 2 8 OVLD Overload 2 8 MU ere E E 2 8 SHIE 2 8 je 2 8 Symbols Sereen 2 8 2 8 T Technical Support i iii Temperature 7 template sod 14 Template Parameters B 14 Threshold nie 8
167. wer left side of the instrument by sliding it out as shown in Figure 1 5 Figure 1 5 Remove Battery With the battery door removed drop the battery into the opening in the case as shown in Figure 1 6 making certain that the battery is aligned with the positive and negative electrodes as shown on the graphic inside the battery compartment Figure 1 6 Inserting Battery Model 820 Technical Reference Manual Getting Started Internal battery life is approximately 16 hours Refer to the description in Chapter 2 of this manual for additional battery information The cable CBL116 SLN serial connectivity kit which allows connection of the 820 to a PC or modem provides the connection of an external power adaptor such as the PSA017 or similar Environmental Considerations The Model 820 sound level meter can be both used and stored in a wide range of temperatures free of moisture and non condensing humidity conditions Moisture will cause the breakdown of an air condenser microphone Some precautions should be taken For example allow the Model 820 ample time to adjust to abrupt temperature changes Condensation may form inside a cold Model 820 if it is brought into a warm room or vehicle and may persist long after the outside case has adjusted to the ambient temperature Also temperatures inside closed vehicles can reach excessive levels Therefore do not leave the instrument in direct sunlight in a vehicle A simple safeguar
168. xceedance to 10 samples after this period 162 Excd Trigger Level Bypass Bypass Enables a variable threshold 163 EXCD Time Start Max Start The exceedance will be mea sured at the beginning Max The exceedance will be mea sured at the maximum Interval History 72 79 MEM INTV No Prompt Entry Comment 72 Intv Enable No Yes Interval report will be stored in mem ory if Yes is entered 73 Intv Exchange 3dB 4dB 5dB 6dB Used to calculate interval integrated level Normally this is set to 3 dB Lag 4 dB gives DOD 5 dB LOSHA 6 dB Avg 74 Intv Threshold 0 to 255 dB Levels above threshold are integrated Model 820 Technical Reference Manual during each interval normally 0 dB for Leg For noise hygiene interval TWA set to dose threshold 75 Intv Period hh mm This sets the period for the interval history from minute up to 99 59 A 1 second interval may also be selected by entering 00 00 76 Intv Time Sync No Yes Synchronizes start of interval with clock and daily history report If Yes is entered the interval report will be started or restarted if already run ning at the start of each hour or min ute depending on Intv duration 77 Intv Save L s No Yes Selects whether interval L s are stored The L s stored are those in effect 1tems 55 60 at end of interval 79 Intv Auto Stop No Yes If

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