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720 Manual.book - The Modal Shop, Inc.

1. Example E9 __2 Overload count from current record E 1 Date and Time of Occurrence ddmmmyy hh mm ss E2 Duration hh mm ss mm ss ss TWA nnn n dB E4 SEL nnn n dB E5 Lmax nnn n dB E6 Lpeak nnn n dB E7 UnWeighted Peak nnn n dB E8 Peak Exceedance Count nnn EQ Overload Counts nnn E 10 Illegal Indication BEEP ILLEGAL E25 EXCD SYMETRY nnn nn E 101 Excd Variables 1 10 Macro Interval History Variables Brackets in the syntax indicate optional characters and Syntax Response I nterval var_no Intv_var Examples 151 1 1 5 11 5 01Jan1997 01 25 00 01Jan1997 01 20 00 from 5 previous 01Jan1997 01 30 00 from 5 after 6 7 05 27 Date and Time of Occurrence ddmmmyy hh mm ss 12 Duration hh mm ss mm ss ss 13 TWA nnn n dB 14 SEL nnn n dB 15 Lmin nnn n dB 16 Lmax nnn n dB 17 Lpeak nnn n dB 18 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 113 nn 1 Lnn 114 Ln 1 nnn n dB 115 nn 2 Lnn 116 Ln 2 nnn n dB 117 nn3 Lnn 118 Ln3 nnn n dB 119 nn 4 Lnn 120 Ln 4 nnn n dB 121 nn5 Lnn 122 Ln5 nnn n dB 123 6 Lnn 124 Ln6 nnn n dB 1101 Intv Variables 1 24 Macro B 28 Model 720 User Manual 6 7 05 Log Variables B
2. B 16 Clock real time iore aai A 9 9 clock eer vie 8 7 Commands Status oos REG A B 6 Criterion 8 12 2 sound level sss C 3 D Daily History sees 8 16 Data determine 9 1 Did A 8 7 De output specifications A 7 Decibel iin nati C 3 Department of Defense level C 5 Detectors id 8 11 C 5 Display A 9 Duration measurement sees C 9 Dynamic range eee 1 5 E EEPROM Register ir es 8 5 Environment effects of Temperature A 6 Erro HUS UH DIR BR Re RE Ede 32 messages and warnings B 32 Error Checking L Qut sie ettet B 23 Exceedance 5 7 8 8 13 Exceedance diagram 7 10 Exceedance History 8 14 Exchange Rate sss 8 11 gl ssaty scu ees C 5 Exchange Rate Factor glossaty 5 Exposure Factor 1 5 5 Sb ete C 6 ACOUSTIC s onc toc erre erbe ec C 6 A 6 Formatting Conventions 1 3 C 6 Frequency band pass filter C 7 A A C 6 Hz T
3. 4 066 32 0 5 066 3 Excd History Enable _No Setting Parameters Option Parameters Responses are denoted by x for option parameters and n if numerical parameters Option parameters can be set in two ways a option number and b actual option text a Option Number Syntax Response S et item number option number lt cr gt lt lf gt Example 9 3 sets setting 9 Baud Rate to option 3 which sets the baud rate to 9600 Example S66 1 sets Excd History Enable to Yes Example S84 0 sets Hist Period Units to _1 32s Example S84 1 sets Hist Period Units to _1 0s Querying an option parameters with a flag of 2 will return the parame ter s value enclosed in brackets as needed when using the option text b Option Parameters Text Option parameters texts is preceded by a semicolon and enclosed by brackets Index settings text must include the same number of characters that are given when queried including spaces which are indicated syntax below with Syntax Response S et item number option text lt cr gt lt lf gt Example S9 _9600 sets Baud Rate to 9600 Example S66 Yes sets Excd History Enable to Yes Example S84 1 32s sets Hist Period Units to 1 32s 6 7 05 B 15 Example S84 _1 0s set
4. B 26 Interval History Variables sees B 27 Run Log Variables aia Ge pee bn idle ih May B 29 Calibration History Variables essere B 29 Time History Variables eiie tee e Ue n EH RR ARE B 29 Histogram Table Variables esses B 30 Print Commands rue ter END E REA B 31 Error Messages and Warnings cc ccsccssessesesceseceeceseeecnsceseeeeeeseeesecaeenaeenseeaees Appendix C Glossary Appendix D Warranty Customer Satisfaction Introduction Welcome to the LarsoneDavis Model 720 Your new hand held Model 720 from Larson Davis is a combina tion Type 2 precision integrating sound level meter and a statistical data logger that exceeds all worldwide accuracy requirements for the measurement of noise The Model 720 measures sound with the ease of opera tion of a point and shoot sound level meter The lat est advances in surface mount technology pre polarized electret microphone and internal firmware have been combined in a rugged lightweight yet extremely versatile unit Many sound level meters in the market can create sig nificant measurement errors because of their limited dynamic range pulse range and crest factor The Model 720 does not have these limitations Furthermore its internal firmware is designed to accommodate changing regulations and to overcome sound measurement problems While the Model 720 is the size of a dosime
5. 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 O before the new number will remove any prior parameter set tings Follow these steps to access the parameters using numeric values Step 1 access parameters using numeric values press Step 2 Press 0 and then 6 The number 6 is assigned to the Current Time parameter Features Especially important information is shown in italics for example To access items 48 50 Overall Exchange Rate Overall Threshold Overall Criterion press the v key 1 4 The Larsone Davis Model 720 meets the requirements of the American National Standards Institute ANSI 51 4 International Electrotechnical Commission IEC 651 and 804 1985 standards for Type 2 accuracy and offers the following features Model 720 User Manual 6 7 05 6 7 05 Dynamic range of more than 100 dB for error free measurements Impulse measuring range greater than 100 dB Standard microphone allows measurements typi cally between 30 and 140 dBA in one range Multiple detectors provide simultaneous RMS and PEAK measurements Leg integrated level duration ranging from 1 sec ond to 99 hours manually controlled Measures FAST SLOW Unweighted PEAK Weighted PEAK Impulse Leg LDOD LOSHA Dose Projected Dose TWA Sel Le Lmax L
6. Run time Clock A 9 Standards Met sarta a lia A 10 Power SUDDly 5 sse dela hosted te aee det o A 10 Dimensions Weight with Microphone Preamplifier and Battery A 10 Serial Port Interface Remote Control B 1 Model INT002 Interface Cable esses B 2 Daisy Chain Addressing tee deed edes B 2 Commands ind stetit eid tree B 3 History Oriented Commands sse B 4 Mode Command RH edt et Ei rens B 5 Read Variables ee E ar IN eo B 6 Other Read Commands zo ue RR REN ete e B 12 Group Read 1 enne nennen nennen B 12 Querying and Setting Parameters seen B 13 Querying Parameters essen enne enne nennen nnne B 14 Setting Parameters cue eto cidad B 15 Option Parametros MER ets B 15 Numeric SA B 16 Character String Parameters sse B 16 Template Parameters oc eR BR Ms B 16 Parameter List A e t n c te T ete B 18 Histogram 21 Tailored Report ede EDEN bre eere 21 22 Error Checking stati is B 23 History Records eee uetus ede e REESE TRI B 25 Types of Historicos ett ie ROI Ba ian B 25 Advance eee REN RN RR T Rs B 26 Backups d RR B 26 Eid LANCE LI RUD em ot te et Ct M obo Tete B 26 History Data Variables vierte ee tene ied B 26 Exceedance History Variables 2
7. 6 7 05 Parameters 8 19 8 20 Model 720 User Manual 6 7 05 CHAPTER Memory Usage Each of the Model 720 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 information 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 Interval Records Intv History Enable Yes Prm 72 Options add bytes shown if enabled Bytes Basic Interval Record Intv Save L s Yes Prm 77 6 7 05 Memory Usage 9 1 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 0d B Peak UwPk Max Wind 0 1dB Peak UwPk Max Wind Other Histories and Memory Usage 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 Estimating Memory Usag
8. 4 4 CanceL Figure 0 4 3 Shift Level 3 Alpha numeric Keyboard Step 1 To enter a name for example turn the Model 720 on and press these keys to access the first name field Modify 0 2 Enter Step 2 Press Modify Step 3 Press Step 4 Press SHIFT twice Model 720 User Manual 6 7 05 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 clear ing the field hit c to return to the original title Repeat a and b in Step 5 to return to this point Enter the L key second from the lower left The cursor will automati cally move to the next letter Enter the A key Enter the 6 287 5 keys con secutively 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 6 7 05 Step 5 Step 6 Step 7 Step 8 Press SHIFT three times Example To enter the company name of Lar son Davis in the first line follow these steps a To access the Name Display turn on the meter Press Modify OQ Enter b Press to place the cursor at the begin ning or use the 4 or gt to position the cursor c To clear the field if necessary press twice and the 4 key d The letter L is on the S field Press SHIFT e
9. 6 7 05 Parameters select what functions are enabled and determine how the measurements are performed Set tings can be both queried and set The settings num bers provided below in the Parameters List section are for both the Query and Set S commands See Chapter 8 for additional information There are four types of settings Option eg Sun Mon Tues Sat Numeric e g 123 45 Character e g Gas Flare Test 1 can be up to 30 characters e Template e g hh mm ss Brackets indicate optional characters and operands cr carriage return lf line feed _ space Querying Parameters When querying a parameter begin the query com mands with Q Brackets indicate optional characters and operands cr carriage return lf 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 Option number for option parameter Flag values may be added together for desired combi nations Example Response 1 066 No 2 066 1 History Enable No 3 Q66 2 14 Model 720 User Manual 6 7 05
10. Normal Printout eene eren 10 1 Printing Reports D Oe HP iS 10 2 Appendix A Specifications A 1 A 2 Reference Direction eae e ie ee t eie A 2 Measurement ROBE aiii a verbe evene A 3 RMS Detector ceo A 3 Other Detector ti AS Aaa A 3 Reference o e ptu A 3 Frequency 4 Detector Time Weightings ii Re aie 5 Effects of Temperature 2 6 Effects of idea adictas 6 Limits of Temperature and Humidity 6 Positioning of Instrument and Observer for Best Measurements 6 AGand DC I SUR 6 ra ee EROR 7 DC 7 Reference Frequency od hota sees A 7 Stabilization Time suse aida 7 Microphone Electrical 8 Functions re e RR OR 8 Data 8 Data Communicati ONS eed RECENSET Rae Edited etate gest A 8 Digital Display skies eee EE nes 9 Digital Display Resolution essen enne 9 Display 5 ete RE POESIE 9 Real time aias n 9
11. The Overall Criterion has been set at 90 parameter 50 Step 2 Press the gt i key to see the fourth screen for Projected Dose 27 87 6 7 05 Performing a Measurement Reading the Data 5 11 The Revision number and date are shown Eight additional screens are avail able from this function Warning or Error messages encountered during normal operation will be displayed here in the order they happen They are accessed by either the 4 and 21 keys or the and x keys which will scroll only the warning messages MEMORY 5 12 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 revi sion Step 1 Access the Battery display by pressing GHIFT and Press the key to access the second screen Step 2 access the Battery c screen press the 0 key To view warning or error messages press the x key Memory will be addressed in Chapter 9 but it would be well to examine the key functions here Stan dard memory size is 64 Kilobytes Three screens are available from this function Model 720 User Manual 6 7 05 This screen shows the percentage of memory left of the total available 55099 divided by 55197 99 82 Total Exc
12. broadcast command can be sent sending an address of zero CHR 128 all units on the chain will become addressed and accept the commands that fol low Only the device with an address of 1 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 WARNING These devices cannot be just paralleled together That would short outputs together and damage the instru ments Use the designated cables Commands The commands are a series of ASCII characters with an alpha command and one or two numeric operands fol lowed by a charge return ASCII 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 The following tables summarize all of the commands and are listed in this order mode control commands first parameter commands next data extraction com mand and report data download command last Square brackets indicate optional characters or operands Syntax R ead variable number operand 2 Response variable value S et parameter number parameter value acknowledge S et parameter number option number acknowledge S et parameter number option text
13. example Key means that a key such as S caused the action Run The following actions Run Stop Pause Cont Reset Mark can be produced by one of the following causes Key LO TIMER CAL INTV BATT or HALT Note that most of the causes are triggered by software The Log information indicates that the measurement was stopped by keystroke If a low battery had been the reason for the measurement stop ping BATT would have appeared To retain data already gathered the Model 720 will terminate the mea surement when battery power becomes low Step 1 Press SHIFT and and several screens become available Step 2 Press the b key for the next screen Step 3 Go back to LOG a by pressing the gt key Scroll through the record logs by pressing v Step 4 The z and keys may be used to look at additional records Press the gt to look at associated dates and times Interval History 6 7 05 The Interval 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 on L s Listed below is each parameter and a brief explanation of its function History Functions 7 5 With this item set to Yes the Inter val Time History is enabled Note Be sure that total memory require ments do not exceed available mem ory Thi
14. key 0 5 Step 9 Pressingthe v key again will scroll loop you back to the SLM original screen 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 To access these parameters turn the Model 720 on by pressing Next press Modity 3 9 Enter Or press the following screen will appear Step 2 The Detector prompt has three possibilities indicated above Press 0 to access desired setting and Step 3 To set the Frequency Weighting press to item 40 You can choose either A or C weight ing A A16 C16 Flt Step 4 The Model 720 has been preset at A To change the setting press M tothe pre ferred setting and Enter Model 720 User Manual 6 7 05 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 weight ing simulates the human hearing at higher sound levels Emax Lmin 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 number of times the current reading has reached predetermined levels selected in parameters 61 62 In this example parameter 61 was set to 55 dB and C weighted param eter 40 In this measurement the RMS has topped this level 11 times Step 5 Find item 41 by pressing
15. minute time history are desired to identify disturbance pattern The following completed work sheet shows the calculations for this example Exceedance Memory Estimation Bytes needed Basic Exceedance Record Save Full Accumulator and Count in Binary aux Cntl Reg bit value 16 prm210 TOTAL Bytes Excd sum lines gt gt gt gt gt gt 1 2 Anticipated Excd Day Enter gt gt gt gt gt gt Number TOTAL Excd Bytes Day Multiply gt gt gt gt gt gt lines 3 amp 4 6 7 05 Memory Usage 9 3 Interval Memory Estimation Bytes needed 6 Basic Interval Record 34 4 34 7 Intv Save L s Yes Prm 77 18 4 18 8 Intv Save L Table 384 0 9 TOTAL Bytes Intv sum lines gt gt gt gt gt gt 52 6 8 10 Anticipated Intv Day Enter gt gt gt gt gt gt 24 Number 11 TOTAL Excd Bytes Day Multiply gt gt gt gt gt gt 1248 Time History Memory Calculation lines 9 amp 10 Bytes Hist Resolution Hist Save Peak 1 0dB No 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 24 hours divided by Hist Period in hours Enter Number Calculate i e 24 60 sec 3600 sec per hour 1440 TOTAL Hist Bytes Day Memory Use per Day Calculation Multiply lines 23 and 24
16. of the following types A Weighting A filter that adjusts the levels of a frequency spectrum in the same way the human ear does when exposed to low levels of sound This weighting is most often used for evaluation of environmental sounds See table below B Weighting A filter that adjusts the levels of a frequency spectrum 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 spectrum 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 frequency weighting selection Center Frequencies Hz Weighting Network Frequency Response 1 3 1 Octave A B C 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 Model 720 User Manual 6 7 05 Leq Level dB Measurement Duration T Microphone Guidelines 6 7 05 Center Frequencies Hz Weighting Network Frequency Respon
17. time history siie B 29 beber lt C 19 W Warnings error messages 32 2 1 warranty AAA 1 6 Wavelength l glossary A A 19 Wavenumber 19 Weighted 8 hour time weighted average sound Levels gessi C 5 Index 4 Weighting etienne iii 8 11 frequency 7 UME 52x edat C 19
18. 10 Printing a Report Turning gathered data into a printed report 1 2 Model 720 User Manual 6 7 05 About This Chapter Appendix A Specifications A listing of acoustic electronic environmental and physical characteris tics of the Model 720 Appendix B Model 720 Serial Port Interface Remote Control Setting interface commands with their syn tax Appendix C Glossary Definitions of key terms and concepts used commonly in the sound industry Appendix D Index Alphabetical listing of all major components of this manual Specifically this introductory chapter covers the fol lowing topics Formatting Conventions Formatting Conventions Explanation of the fonts and other formatting conventions used in this man ual Model 720 Features A listing of the featured charac teristic and capabilities of the Model 720 Model 720 Components Description and diagrams of the Model 720 external parts Getting Started Instructions for unpacking a list ing of accessories and optional equipment and ini tial setup This manual uses the following formatting conven tions 6 7 05 Introduction 1 3 Functions accessed by pressing key on the Model 720 keypad are shown with an icon for example Press e and then press Cancel 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
19. 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 Step 2 Press the b key to access the five screens available in the EXCD mode including Dura tion Leg Lmax Pk UWPK Step 3 examine the properties of each exceedance record use the v key for each of the five screens The PassBy Function is a special exceedance event detector that measures the Linaw 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 craft passby or other event noises such as blasts or gas get ting noise In addition to the levels measured the date and time of the L and the duration 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 exceed ance is reduced Step 1 To enable the Passby function turn on the Model 720 and then press 162 and Enter The screen will show either of two options Level PassBy History Functions 7 11 The occurrence time or Maximum Step2 Press and then press 0 to Level must be equal to or greater PassBy and then press Enter than the RMS EXCD LVL 1 parameter 61 Passby s Max Start of Exceedance Occurrence Time Duration Figure 0 2 Passby Di
20. AC Out Weight ing which has the values listed here Choose one by pressing 0 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 Press to exit setup mode We have already looked at the L and Lj in a pre vious screen These values are also available directly from display keys They can be accessed while the unit is taking a reading or in the stop mode Only when the unit is running is the data recorded These measure ments are usually read after they have been taken and the measurement is stopped Here we will examine them while a measurement is being taken Step 1 Press to view the greatest value of the RMS SPL since the beginning of the measure ment Step 2 Pressthe gt key and examine the second screen available in this series 6 7 05 Performing a Measurement Reading the Data 5 5 The display shows that parameter 62 was set to 65 dB and is C weighted This measurement topped this level 6 times The current measurement Lmin occurred on November 27 1996 at 9 21 A M Remember the Model 720 used military time to designate between A M and P M That Lmin value was 51 5 dB There are no other screens available from this display PEAK UWPK PEAK is a weighted value and repre sents 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
21. Mode Off RMS Peak Type of noise data used by the base mode 8 16 Model 720 User Manual 6 7 05 87 Histogram Resolu tion 1 8 1 2 1 0 2 0 5 0 10 Selects the interval in dB of the overall time level amplitude distri bution Print Options 89 112 s These parameters allow for tailored reports of the Model 720 data during or after the measurement They can be accessed from outside the SETUP by pressing s 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 param eters 92 RMS Histogram No Yes Prints histogram of overall rms levels 93 Lowest Level 0 255 RMS Histogram lowest printed level 94 Highest Level 0 255 RMS Histogram highest printed level 95 Histogram Resl 1 8 1 2 Spacing in dB between histogram 1 0 2 0 5 0 10 entries 96 Peak Histogram No Yes Prints histogram of overall peak levels 97 Lowest Level 0 255 Peak Histogram lowest printed level 98 Highest Level 0 255 Peak Histogram highest printed level 6 7 05 Parameters 8 17 99 Histogram Resl 1 0 2 0 5 0 1
22. Note that the run time for LDL and OVERALL is always the same A new measurement may be started at any time with out effecting the Overall Dose using the Current Dose settings by modifying the CURRENT exchange rate and threshold settings An automatic reset occurs 5 8 Model 720 User Manual 6 7 05 The appropriate value for this parameter is established by enforce ment authorities in various coun tries In the USA OSHA mandates a 5 dB exchange rate 3 dB is com mon in most other countries Note that these can be changed with out a Reset all The normal Dose setting for thresh old is 80 dB which allows the instru ment to virtually ignore sound below that level as it does not con tribute significantly to the weight of the measurement data sought and saves memory as well 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 6 7 05 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 minute to examine the parameter values avail able all of which will effect the measurement The Current Exchange Rate parameter item 45 is accessed by the following steps Step 1 Press 9 Modify 4 and 5 then Enter The choices here are listed below 3dB 4 5dB 6dB The Current Threshold
23. 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 R 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 i 6 7 05 B 9 109 _RMSEX2 RMS Exceedance Flag 2 R 110 _ PEAK Exceedance Flag a R111 _UWPKEX UWPK Exceedance Flag R 112 _OVLD System Overload Flag R 113 _ Excd Exchange Rate Text CCCCC R 114 _IVXR Intv Exchange Rate Text CCCCC R 115 _AUTOADV Auto Advance History Ind 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 141 _IVSEL Interval SEL nnn n dB R 142 _IVMAX Interval Lmin nnn n dB R 143 _IVMIN Interval Lmax nnn n dB R 144 _IVPEAK Interval nnn n dB R 145 _IVUWPK Interval UnWeighted Peak nnn n dB R 146 _HISTLEQ AUTO SEND HISTORY LEQ nnn n dB R 150 RUNONT Number of RUNS amp CONTINUES nnnnn R 151 POFAULT Power On Fault Cause Character c D Data Checksum Corrupt E EEPROM Checksum Corrupt K Key Reset 4 RESET 1 On P Parameter Checksum Cor rupt O Opcode Error R RAM Setup Register Corrupt T Test Memory Corrupt W Watchdo
24. RESET ALL Q2 Q HDG1 HEADING LINE 1 Q3 Q HDG2 HEADING LINE 2 Q4 Q HDG3 HEADING LINE 3 Q5 Q TITLE MEASUREMENT TITLE Q6 Q TIME CURRENT TIME Q7 Q DATE CURRENT DATE Q8 Q DAY DAY OF WEEK Q9 Q BAUD 1 BAUD RATE Q 10 Q SADDR COM1 ADDRESS Q 12 Q HS COM PORT HANDSHAKING REGISTER Q 14 Q LOGIC1 OUTPUT 1 LOGIC Q 15 Q OUTI2TIM OUTPUT 1 HOLD TIME Q20 Q PWRSV POWER SAVE OPTIONS Q 21 Q TIMMD TIMER MODE Q 22 Q RUND TIMER RUN DATE Q 23 Q STOPD TIMER STOP DATE 24 Q RUNT1 TIMER RUN TIME 1 Q25 Q STOPT1 TIMER STOP TIME 1 Q 26 Q RUNT2 TIMER RUN TIME 2 Q27 Q STOPT2 TIMER STOP TIME 2 Q 28 Q LKCOMB LOCK COMBINATION Q29 Q LKRS LOCK R S KEY B 18 Model 720 User Manual 6 7 05 Q 30 Q LKSU LOCK SETUP Q 31 Q LKFN LOCK FUNCTION Q 32 Q LKRES LOCK RESET Q 33 Q LKPWR LOCK THE ON KEY Q 34 Q LKIO LOCK I O Q35 Q CALLVL CAL LEVEL Q 36 Q CALSN CALIBRATOR S N Q 37 Q AUTOCAL AUTO CALIBRATION MODE Q 38 Q CALTIM AUTO CAL TIME Q39 Q DETC DETECTOR Q 40 Q WGHT FREQUENCY WEIGHTING Q 41 Q ACOUT AC Out eighting and Gain Q 42 Q PkWght UwPk Detector or Weighting Q 44 Q REFLVL RELATIVE LEVEL REFERANCE see R 54 Q 45 Q CXRATE CURRENT EXCHANGE RATE Q 46 Q CTHOLD CURRENT THRESHOLD Q 47 Q CCRIT CURRENT CRITERION Q 48 Q OXRATE OVERALL EXCHANGE RATE Q 49 Q OTHOLD OVERALL THRESHOLD Q 50 Q OCRIT OVERALL CRITERION Q 51 Q DOSET DOSE PERIOD Q 52 Q LDLXRATE LDL
25. User Manual 6 7 05 Sound Pressure 6 7 05 SE Ti T Poa 2 Pol SEL 1010210 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 reference pressure of 20 Pa and T is the ref erence time of 1 second It is then put into logarithmic form It is important to note that it is not an average since the refer ence time is not the same as the integration time The physical characteristic of sound that can be detected by microphones Not all pressure signals detected by a micro phone 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 several ways this can be done Moving Average The averaging process is continually accept ing new data so it is similar to an exponential moving aver age The equation for it is t z p e 9 ag t Prms 5 The sound pressure is squared and mul
26. carriage return lt 1 line feed Denoted in syntax by history no 1 Exceedance E 2 Interval 3 Daily D not available on 720 4 Run Log L 5 Calibration C 6 Time H 7 Histogram Table T Advance Advance a number of records from present record number If no num_record number of records is pro vided 1 is assumed Syntax Response A dvance num record history no lt cr gt lt lf gt Example A9 5 Adavnces calibration history by 9 records Backup Backup a number of records from present record num ber If no num record number of records is provided 1 is assumed Syntax Response Backup num record history no lt cr gt lt lf gt Example B9 5 Backs up the calibratoin history by 9 records from the current calibration history Find Find record number directly Syntax Response F ind rec no history no lt cr gt lt lf gt Example F9 5 Locates calibration history record 9 History Data Variables Generally you use the Find command to get to the first record F1 2 and the Advance command A to move up through the records Exceedance History Variables Brackets in the syntax indicate optional characters and operands Syntax Response B 26 Model 720 User Manual 6 7 05 E xceedance var_no Excd_var
27. copy copy to 29 Bytes 9 4 Exceedance History bytes day from line 5 Model 720 User Manual 6 7 05 Memory Use per Day Calculation Bytes Interval History bytes day from line 11 Time History bytes day from line 22 Run Log bytes day n number of Run Log records day 2 nx20 X 20 n x 20 bytes record Calibration Log bytes day 1 17 17 n x 17 bytes record Setup RAM Registers bytes used n number of registers stored day 0 nx506 n x 506 bytes record TOTAL bytes used day Sum lines 23 29 15 705 Model 720 s Memory Size 64000 See SYSTEM b 64 000 6 7 05 TOTAL Run Time in days until out of memory Divide line 31 by 30 Memory Usage 4 07 9 5 Model 720 User Manual 6 7 05 CHAPTER Printing a Report The Model 820 allows for tailored reports of data dur ing and after measurements In this chapter we will access the printing option parameters for Normal Printouts and print a report Normal Printout Parameters Before proceeding with printing baud rate needs to be determined and entered Set parameter 9 to proper baud rate determined 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 E Normal printouts can be accessed from outside the SETUP mode by following thes
28. date shown on the screen Parameter 63 sets the level above which the readings must go to be recorded by the Model 720 Parameter 63 controls the setting for this measurement Here the setting is 74 dB C weighted and in this measurement was exceeded 46 times 5 6 Step 3 Pressthe key to find the third screen The same key V finds the Lmin values in conjunction with the SHIFT key Step 1 Examine these values press the SHIFT and keys and the following display will appear The Model 720 also has a peak level detector Its values during the measurement or when stopped are found by pressing the key Step 1 Access Peak values Press 29 Step 2 The second display available from this func tion is accessed by pressing the 0 key Model 720 User Manual 6 7 05 The unweighted peak value is the unfiltered no A or C weighting sig nal from the Peak Detector The value for the UWPK is set in parameter 64 and is 85 dB This value was reached 30 times 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 Unweighted Peak UWPK has two screens available as well and are accessed with the SHIFT a
29. four user defined L s and more min User selectable dose exchange rate criterion threshold and reference duration Measures and stores more than 40 000 different DOSE combinations in a single measurement Allows comparisons of different DOSE standards using the same data Complete data logging capabilities with 64 Kobe standard memory Time history sampling periods are user selectable from 1 second up to one sample every 255 seconds Quartz clock calendar system for data annotation Calibration from front panel using an appropriate calibration 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 L D cable 035 for longer measurements Introduction 1 5 Model 720 Components 1 6 RS 232 computer interface standard All functions fully programmable Comes complete with PC SWW_SLM_UTIL software for data retrieval and translate binary files to ASCII format Other PC software also available Large two line 32 character high contrast LCD dis play Small 20 x 7 5 x 2 5 cm HWD 8 x 3 x 1 and with out the nose cone 15 x 7 5 2 5 cm HWD 6x3x 1 and lightweight 326 g 11 oz including micro phone and battery Rugged ABS case with EMI and RFI protection Environmental enclosures available for system security and protection from inclement weather conditions Durable membrane keypa
30. ideal for unattended measurements and time stamping of events The 64 KB memory can be used to store time exceed ance 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 LeD PC com patible software employs a binary data dump method for even faster data transfer External battery or DC 1 10 Model 720 User Manual 6 7 05 Getting Started Unpacking and Inspection 6 7 05 power may be supplied through the same five pin con nector This section outlines the steps you need to follow when you first receive and unpack the Model 720 The following topics are covered Unpacking and Inspection e Accessories and Optional Equipment Connecting Internal or External Power Environmental Considerations Preparing to use the Model 720 You will then be ready to use the Model 720 for actual measurements as described later in Chapter 4 of this manual Your Model 720 has been shipped in protective pack aging Please verify the package contents with the fol lowing list Accessories and Optional Equipment and retain the shipping containers for safe shipment at a future date Report any damage or shortage immedi ately to Larsone 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
31. key is pressed in order to interpret the keyboard event Therefore where possible do not press the B key during a valid event you wish to measure The first screen shows the percentage of power left in the battery the inter nal power source INT the second display indicates external power is being used EXTV Step 1 To manually check battery voltage simply press the GHIFT keys Information sim ilar to the following will display Turning Off the Model 720 The instrument will not allow itself to be turned off until in Stop mode This feature will insure that no important data is lost 2 10 To turn off the Model 720 simply press the SHIFT key Model 720 User Manual 6 7 05 Calibration Because of variation in microphone sensitivities a sound level meter must be calibrated to a reference sound level for accurate measurements This is easily performed with the Model 720 You will need a cali brator with an appropriate adapter for the Model 720 microphone such as the LarsoneDavis CAL150 This L D calibrator outputs 114 dB or 94 dB with respect to 20 pPa and at a frequency of 1000 Hz At this fre quency 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 measure ments in th
32. m and 10 p m have 5 added to them to represent a lessened toler ance for noise during evening activities They are energy summed and converted to an average noise exposure rating Criterion Duration T Itis the time required for a constant sound level equal to the Criterion 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 2 Model 720 User Manual 6 7 05 will produce 100 Noise Dose See Noise Dose Standard ANSI 12 19 Criterion Sound Exposure CSE The product of the Criterion Duration and the mean Criterion Sound Level L square sound 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 T 10 Standard ANSI 1 25 It is the sound level which if continually applied for the Cri terion Duration will produce a Noise Dose of 100 The cur rent OSHA Criterion Level is 90 dB Standard ANSI 512 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 gener ally shorter so the sound energy is spread out over the Crite rion Duration period
33. mak ing certain that the battery is aligned with the positive and negative electrodes as shown on the graphic inside the battery compartment Internal battery life is approximately 16 hours Refer to the description in Chapter 2 of this manual for addi tional battery information The cable CBL116 SLN serial connectivity kit which allows connection of the 820 to a PC or modem pro vides the connection of an external power adaptor such as the 5 017 or similar Alternatively you may use an external power source via pin 1 GND and pin 4 of the 5 pin connector To do this order cable 035 from Larson Davis The Model 820 accepts 7 16 Vdc amp 30 mA and is internally fused at 0 5 A An internal battery with a full charge will retain memory for 3 months with the instrument off Introduction 1 15 Caution Weak batteries should always be replaced Discharged bat teries will cause memory loss and may leak and damage the Model 720 Always turn the instrument off and disconnect external peripherals before removing the internal battery Failure to do so may cause data loss Do not press ON while there is no battery in the SLM The instrument will turn off when the usable bat tery capacity drops to 10 This will leave approxi mately 1 month of memory retention Before turning off four low battery messages will appear one every 16 seconds After 64 seconds the instrument turns itself off With the bat
34. of the Model 720 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 communi cations you may have with Larson e Davis Inc Introduction 1 11 Accessories A good quality alkaline cell should provide more than 16 hours of Model 720 operation Since most recharge able cells have less capacity expect shorter use Wind noise can adversely affect mea surements Using the windscreen on the microphone reduces wind noise and protects the element from dust and bumps Optional Equipment 1 12 The Model 720 is delivered with the following standard accessories The standard Model 720 Precision Sound Level Meter including a Model M1 3 8 air condenser microphone and Model 789 preamplifier Alkaline battery 9 volts IEC GLR61 or NEDA ANSI 1604A e User manual Soft belt pouch LeD part 5009 e WS002 a 3 8 inch mini windscreen e SWW_SLM_UTIL software Utility software package allowing data retrieval and translation of binary files generated by the Model 720 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 The following optional equipment is also available e CBLO033 Printer cable for direct printout to serial printer 6 feet e CBL034 Connects Model 720 and un wired
35. 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 Block Run Time 1 on Run Date 2 day to 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 land 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 6 7 05 Parameters 8 9 Lock 28 34 UL For complete instruction on setting These parameters limit access of certain functions to those with the correct password Step 1 the Lock parameters see chapter 6 Step 2 After setting password and lock options exit the setup and press SHIFT to lock To unlock press GHIFT then Modify and enter the password No Prompt Entry Comment 28 Lock Password 8 characters Enter your password 29 Lock R S Key No Yes Lock mode change 30 Lock Setup No Yes Lock changes to setup 31 Lock Function No Yes Lock changes to displayed func tion 32 Lock Reset No RES ALL Lock m
36. provided by R98 All error messages begin with CHR 7 ERROR Error Code Message 1 COUNT OVERFLOW 2 EXPONENTIAL OVERFLOW 3 RTX TASK SELECT 4 ILLEGAL EXCHANGE RATE 5 UNKNOWN INTERRUPT 6 WATCHDOG RESET 7 RAM BANK ERROR 8 OPCODE ERROR All warning messages begin with CHR 7 WARN ING Warning Message Code 128 Out of Memory 129 Battery Low 130 POWER FAILURE 131 DIVISION BY ZERO 132 Operand 1 Range 133 Operand 2 Range 134 DPC Format 135 Key Has No Effect 136 Stop Required B 32 Model 720 User Manual 6 7 05 137 Key Has No Effect In VIEW 138 Parameter Entered Wrong 139 RESET ALL Required 140 Use ARROWS ON to Exit 141 Use NEXT PREV or ENTER 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 I O Operand Invalid 151 Unable to Calibrate 152 EEPROM Write Error 153 Memory was Lost Data Reset 154 RECALL Not Found 155 Function Not Implemented 156 System Locked 157 A D Stack Full 158 A D Over Run 159 Serial Port Framing 160 S
37. shows the pro duction date and the serial number uniquely assigned to your Model 720 This message appears for only 1 or 2 seconds This screen will remain until the user inputs other commands The flashing uppercase S indicates sys tem 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 720 is in STOP mode Step 2 The next display automatically appears The third screen appears almost immediately showing the title information for the current or last reading and is programmable by the operator At this point you can change the parameters and begin taking actual measurements Checking the Battery Voltage WARNING 6 7 05 The Model 720 continuously monitors its battery volt age to ensure accurate measurements It has a battery life of about sixteen hours It will turn off automati cally 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 Do not press the key during a measurement since it will pause the measurement while pressed Overview to Model 720 2 9 Remember pushing a button can produce small low level noises which can affect your readings In addition the Model 720 momentarily pauses the current measurement whenever a
38. the customer s purchase price for any LD product with which the buyer is not completely satisfied subject to the exceptions contained in Paragraph J of this Limited Warranty The option of a refund may be selected during this one 1 year period in lieu of repair replacement or exchange of the product Extended Labor Warranty In furtherance of LD s commitment to Total Customer Satisfaction LD offers an extended labor warranty of one 1 year on all products calibrated or certified by a factory technician at any time or from time to time during the first seven years of the product life from date of manufacture The customer s sole remedy pursuant to this extended warranty is to receive free labor for any repairs required during the period in which the extended warranty is effective This extended labor warranty is subject to the limitations as outlined in Paragraph J Service amp Repair Limited Warranty In addition to the limited warranties set forth above LD offers a 90 day parts and labor limited warranty for all repair work performed at the factory This warranty is limited to parts repaired or replaced at the factory by LD This warranty is also subject to the limitations as outlined in Paragraph J C Shipping Charges The buyer will return the product freight prepaid by the Buyer to an authorized service center The product will be returned to the buyer freight prepaid by LD D Products Manufactured by Others This Limited Warranty does
39. unattended measurements i e one or two measure ments day between two dates or a single block measurement from a start date and time to a stop date and time WA TAKT The German Takt Maximal Lev els TWA Shows the overall TWA and Run Time DOSE The Dose and Projected Dose sound exposure percentages are dis played in these screens Parameters 48 51 control the Dose measurement LDL Logged Dated Logic allows the user to recalculate TWA SEL DOSE and Pro jected Dose using new Exchange Rate Threshold and Criterion parameters during or after a measurement 2 6 Model 720 User Manual 6 7 05 Functions Arrows Up Down Left and Right arrows are used to change fields to modify information within a given field and can be used in conjunction with other keys to allow other functions Modify Prepares the field for changes while in setup Getting to Know Screen Symbols 6 7 05 Symbols basic to the Model 720 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 exam ples 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 Functionality SsS flashing upper case to lower case Model 720 is stabilizing u
40. zero the reference is generally set to be the lowest value of the quantity Department of Defense Level The Average Sound Level calculated in accordance with Department of Defense Exchange Rate and Threshold Level See Average Sound Level Dose See Noise Dose Detector The part of a sound level meter that converts the actual fluc tuating sound or vibration signal from the microphone to one that indicates its amplitude It first squares the signal then averages it in accordance with the time weighting char acteristic and then takes the square root This results in an amplitude described as rms root mean square Eight Hour Time Weighted Average Sound Level rwA g 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 Lrwa s L gLogi 25 NOTE This definition applies only for a Criterion Duration of 8 hours Standard ANSIS12 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 5 frr t dt 2 L ge 1020810 where is the sound pressure and the Measurement Dura tion specific time period 1 See Sound Exposure Level Exchange Rate Q Exchange Rate Factor q Exposure Factor k It is defined in ANSI 51 25 as the change in sound level corresponding to do
41. 0 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 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 num ber of printout 106 Highest Rec 0 65535 Ending exceedance record num ber 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 8 18 Model 720 User Manual 6 7 05 Additional System Functions 159 162 No 159 Prompt Power Mode Entry Normal Ext CO Comment Normal meter uses internal bat tery unless greater external volt age is also applied Ext CO external cutoff when external power falls below 10 5 V meter turns off to prevent battery damage 162 EXCD Trigger Level Passby Passby Enables a variable thresh old
42. 0 to 255 dB 100 dose if this level is main Criterion 1 tained 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 inte Threshold 2 grated into overall TWA or Dose readings 50 Overall 0 to 255 dB 100 dose if this level is main Criterion 2 tained for full dose period Dose 51 54 The noise exposure Dose may be calculated with three different set of parameters Current Overall and LDL See section on occupational noise for additional infor mation The dose displayed with the key is the Overall Dose No Prompt 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 param eters 53 LDL Threshold 0 255 dB 54 LDL Criterion 0 255 dB 8 12 Model 720 User Manual 6 7 05 Ly Statistical Levels 55 58 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 histo gram see item 77 The measured and displayed Lan may be changed during the measurement The four nn are automatically listed in increasing order No Prompt Entry Comment 55 Lnn 1 Percent 0 to 99 56 L
43. 0000 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 0 125 0 2 2000 0 0 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 e Weighted Peak Detector Rise Time 60 ps e Unweighted Peak Detector Rise Time 30 us 6 7 05 A 5 Effects of Temperature Effects of Humidly The SPL level varies 6 0 5 dB when the complete instrument is tested over the 10 C to 50 C tempera ture range The reference reading for this test is taken at 20 C and 36 relative humidity RH the input sig nal 15 at 1000 Hz 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 dissipated Positioning of Instrument and Observer for Best Measurements AC and DC Outputs A 6 Measurements can be made with the Model 720 held in one hand with the arm extended away from the body however better measurements can be made with the Model 720 placed on a tripod The output impedance is 600 34 for both the AC and DC outputs of the Model 720 Fo
44. 1 1 75 0 RMS current bin level T 1 n Level of current bin nnn n dB T 2 n Count of samples nnnnnc c or M for Kilo or Mega TS3 n Percent of total nnn nn 5 Prints the accumulated timer for the current hhhhh mm ss s level bin The table number is optional B 30 Model 720 User Manual 6 7 05 Print Commands Brackets in the syntax indicate optional characters cr carriage return lf line feed Syntax Response P rint print_no lt cr gt lt lf gt Example 1 Data Report is printed to computer 1 sets all report enables in setup to No 177 1 2 sets the Data report Run log and EXCD report enables short to Yes and S178 1 3 begins printing to the computer S192 1 P100 PO Standard Report Formatted from normal setup parameters parameters 89 to 112 P1 Data Report 2 Data amp Histograms P3 Short Full Report Histories with SHORT option P4 Long Full Report Histories with LONG option 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 CANcel transfer mode 2 in a row ASCII CAN or CHR 24 6 7 05 B 31 Error Messages and Warnings The error code or warning code listed is the number
45. 200 bits per second Model 720 User Manual 6 7 05 Digital Display e 2 line 32 digit 7 segment LCD e Full ASCII character set Fully annotated date displays parameter with units Digital Display Resolution e dB levels 0 1 dB Dose 0 01 e Elapsed Time 0 1 second Display Bargraph e 120 dB range 1 dB resolution for SPL Real time Clock Calendar e 24 hour clock hh mm ss e 1 second resolution 100 year calendar 01JAN1999 Automatic run stop timer with two alarms and four alarm times Year 2000 compliant Run time Clock 0 1 second resolution e Format hhhhh mm ss s 6 7 05 9 Standards Met Power Supply Maximum gt 4 years ANSI 51 4 1983 Type 2 ANSI 1 25 1991 Type 2 IEC 651 Type 2 TEC 804 Type 2 Directive 86 188 EEC Directive IEC TC 29 Internal 9 V battery typically 20 hour operation actual run times vary depending on operating con ditions External 7 to 16 VDC 30 mA current drain Battery life indication selected from keyboard or computer program Dimensions Weight with Microphone Preamplifier and Battery A 10 Width 3in 7 5 cm Length 8 in 20 cm Length 6 in 15 cm without nose cone Depth 1 0 in 2 5 cm Weight with battery 11 oz 326 gm Shipping weight 3 Ibs 1 4 kg Model 720 User Manual 6 7 05 CHAPTER Serial Port Interface Remote Control The Model 720 is fully controllable remotely via Serial Port interface Setup ite
46. 6 7 05 System 1 20 RUS The following parameters define measurement names set clock and determine interface parameters Prompt Reset ALL Data Entry No Yes Comment This parameter allows a SHIFT without leaving SETUP Note If this parameter is set to Yes a RESET will occur and the parameter will automatically revert to No Name up to 30 characters Place any message you desire in these 3 lines The 3 lines of name are savable only in EEPROM Title up to 30 characters Used to describe a measurement or setup Current Time hh mm ss also accessed w SHIFT Current Date mm dd yy The 720 is Year 2000 Compliant Leap years are considered For years less than the year manufac tured the 21st century is assumed 2000 2092 otherwise the 20th century is used 1993 1999 Day of Week Sun Sat Baud Rate 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 communica tion mode for a network of LeD SLMs Each must have a unique address Normally only one Model 720 is used thus the address should be set to 0 to dis able 6 7 05 Parameters 8 7 11 RS 232 Handshak None Hdwr XOFF RS 232 handshaking protocol 720 ing Both SW1 uses None 12 COM Ports Hand None Hdwr XOFF Serial han
47. 9 It is the logarithmic average of the sound during a Measure ment Duration specific time period using the chosen Exchange Rate Factor Exposure to this sound level over the period would result in the same noise dose and the actual C 1 unsteady sound levels If the Measurement Duration is the same as the Criterion Duration then Layg LTwA LC 1 Log m qLogio 10 GOV where the Measurement Duration specified time period is T T T and q is the Exchange Rate Factor Only sound lev els above the Threshold Level are included in the integral Standard ANSI 12 19 Calibration 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 L4en A rating of community noise exposure to all sources of sound that differentiates between daytime evening and nighttime noise exposure The equation for it is 0700 1900 2200 2400 Li 10 10 L 10 L 5 10 Li 10 10 1 101080 10 10 10 10 0000 0700 1900 2200 The continuous equivalent sound level is generally calcu lated 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 mid night The levels for the hourly periods between 7 p
48. Choose a microphone for free field or random incidence to minimize 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 frequencies and when the microphone is facing the sound source Rules 1 Do not use a microphone at frequencies higher than speci fied by the manufacturer to increase the frequency response choose smaller microphones 2 Choose a microphone for free field or random incidence to minimize the influence of orientation 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 inter ested in and hold the meter as far from your body as possi ble Use a tripod whenever possible 2 Measure th
49. EL 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 B 24 Model 720 User Manual 6 7 05 History Records Types of History 6 7 05 The various histories of the Model 720 are each accessed in a similar fashion The Find command is the primary method of locating a history record for ran dom nonsequential access For example to find the one hundred twenty fifth Exceedance record you send the command F125 1 lt cr gt where the 1 specifies that it is an Exceedance record to be found as defined in the history_number column above The Advance and Backup commands are generally used next They extract data after the initial find command The Find command takes longer to execute as the record number increases in size therefore for sequen tial data extraction locate the first desired record with the Find command and then use the Advance com mand The relative_rec option can be used to retrieve data forward or backward from the current record number without changing that record number it is a signed 8 bit value i e 1 to 127 is positive 1 to 127 while 128 to 255 is 128 to 1 respectively Refer to parameters 211 through 214 to query the current record number Setting these parameters to a desired record number is an alternate form of the Find command Brackets in the syntax indicate optional characters and operands cr
50. EXCHANGE RATE Q 53 Q LDLTHOL LDL THRESHOLD D Q54 Q LDLCRIT LDL CRITERION Q 55 Q LNN1 Lnn 1 PERCENT Q 56 Q LNN2 Lnn 2 PERCENT 6 7 05 B 19 Q57 Q LNN3 Lnn 3 PERCENT Q58 Q LNN4 Lnn 4 PERCENT Q 61 Q RMSTH1 RMS EXCD LEVEL 1 Q 62 Q RMSTH2 RMS EXCD LEVEL 2 Q 63 Q PKTH PEAK EXCD LEVEL Q 64 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 72 Q IVENB ENABLE INTV HISTORY Q 73 Q IVXRT INTV EXCHANGE RATE Q74 Q IVTHOLD INTV THRESHOLD Q75 Q IVPER INTV PERIOD Q 76 Q IVSYNC INTV TIME SYNC Q77 Q IVLN INTV SAVE Ln S Q 79 Q IVSTOP INTV AUTO STOP Q 80 Q HSTENB ENABLE TIME HIST Q81 Q HSTRES HIST RESOLUTION Q82 Q HSTPK HIST SAVE PEAK Q 83 Q HSTPER HIST PERIOD Q 85 Q HSTBASE HIST BASE Q 86 Q HSTMODE HIST BASE MODE Q87 Q HGRES HISTOGRAM TABLE RESOLUTION Q 89 Q PRNRPT DATA REPORT x Q 90 Q PRNLOG R S AND CAL LOG x 091 x B 20 Model 720 User Manual 6 7 05 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 sam ples in each bin in hex 0 9 amp a There are 1024 RMS bins and 128 Peak and UWPk bins this co
51. Example If the Criterion Duration 8 hours and the specific period is 4 hours and the average level during the 4 hours is 86 dB then the Lgp 4 83 dB Day Night Average Sound Level DNL Lan A rating of community noise exposure to all Decibel dB 6 7 05 sources of sound that differentiates between daytime and nighttime noise exposure The equation for it is 0700 2200 2400 L 10 10 L 10 L 10 10 Lj 1910810 gt 10 gt 10 gt 10 0000 0700 2200 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 mid night to 7 a m have 10 added to them to represent less toler ance for noise during sleeping hours The same occurs from 10 p m to midnight They are energy summed and con verted to an average noise exposure rating A logarithmic form of any measured physical quantity typi cally used in sound and vibration measurements Whenever C 3 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 repre sented more simply It is not possible to directly add or sub tract physical quantities when expressed in decibel form The word level is always attached to a physical quantity when it is expressed in decibels for example L repres
52. FT key ters If you choose to use this feature enter something you won t forget i e a name or birth year and press e 6 7 05 Timed Measurement 6 5 These setup items parameters 28 34 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 function can be used when this Lock function is implemented Press d 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 e The Model 720 is now unlocked and accessible for additional entries 6 6 Step 3 To turn on the Lock press the and M keys When Yes appears press Enter Step 4 If you should wish to unlock the system for further input or readings press GHIFT and 655 then Model 720 User Manual 6 7 05 History Functions The process of measuring and recording units of sound and retrieving the data for study and under standing is enhanced by additional functional capabili ties of the Model 720 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 Deali
53. L Last Level Relative to REFLVL see Q 44 nnn n R 55 TABLE Display Histogram Selected ccc R 56 _COUNT Display Overall Count nnnnnk R 57 _O LEQ Overall Leq nnn n dB R 68 _EXLEQ Total EXCD Leq nnn n dB R 69 _EXTIM Total EXCD Time hhhhh mm ss s B 8 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 Model 720 User Manual 6 7 05 70 _BGLEQ Background Leq nnn n dB R 86 _ Battery Level nnn 87 _BATTSRC Battery Source INT EXT ccc R 88 _ TEMP Temperature nnn n R 89 _SERNUM Serial Number R 90 _REVNUM Software Rev amp Rev Date n nnn ddmmmyyyy R91 _FREEMEM Free Memory nnnnnnn R 92 RECLOG Number of RUN STOP Records nnnnn R 93 RECEXCD Number of EXCD Records nnnnn 94 RECINTV Number of INTV Records nnnnn R 95 RECHIST Number of HIST Records nnnnn 97 _RECCAL Number of Calibration Check 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 99 _LOGIC1 Logic Output 1 State On Off unused R 100 _LOGIC2 Logic Output 2 State On
54. LO RMS HISTOGRAM TABLE LOW VALUE n Q 182 Q RMSHI RMS HISTOGRAM TABLE HI VALUE n Q 183 Q RMSRS RMS HISTOGRAM TABLE RESOLUTION x Q 184 PEAK HISTOGRAM TABLE x Q 185 PEAK HISTOGRAM TABLE LOW VALUE n Q 186 PEAK HISTOGRAM TABLE HI VALUE n Q 187 PEAK HISTOGRAM TABLE RESOL x Q 188 UWPK HISTOGRAM TABLE x Q 189 UWPK HISTOGRAM TABLE LOW VALUE n Q 190 UWPK HISTOGRAM TABLE HI VALUE n Q 191 UWPK HISTOGRAM TABLE RESOL x B 22 Model 720 User Manual 6 7 05 Q 192 EXCD REPORT x Q 193 EXCD REPORT LOW RECORD n Q 194 EXCD REPORT HIGH RECORD n Q 195 INTV REPORT x Q 196 INTV REPORT LOW RECORD n Q 197 INTV REPORT HIGH RECORD n Q 198 HIST REPORT x Q 199 HIST REPORT LOW RECORD n Q 200 HIST REPORT HIGH RECORD n Q 202 Q CALMODE CALIBRATION MODE Q 203 Q ULCOMB UNLOCK COMBINATION cccccccc Q 204 Q IONAME FILENAME cccccccc Q 205 Q ERCHK ENABLE ERROR CHECKING I O Error Checking I O 6 7 05 The error checking I O protocol verifies that com mands and data are transferred without errors To enable error checking the command or 5205 1 command is used To disable error checking two lt CR gt characters in a row may be sent if not in the Modem Mode or the 5205 OF command is sent The is the check character for the 5205 0 com mand A detailed description of the protocol is avail able from LarsoneDavis and the latest revisio
55. Model 720 Reference Manual Larson Davis Inc 1681 West 820 North Provo UT 84601 1341 Phone 801 375 0177 FAX 801 375 0182 www larsondavis com 1720 01 Rev C Copyright Copyright 2003 by Larson Davis Incorporated 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 Larson Davis Inc Disclaimer The following paragraph does not apply in any state or country where such statements are not agreeable with local law Even though Larson Davis Inc has reviewed its documentation Larson Davis Incorporated 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 Larson Davis Inc This publication may contain inaccuracies or typographical errors Larson Davis 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 Larson Davis 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 in
56. OF STATUTE OF LIMITATIONS ANY REPAIRS PERFORMED UNDER THIS LIMITED WARRANTY SHALL NOT IN ANY WAY EXTEND THE STATUTES OF LIMITATIONS FOR CLAIMS UNDER THIS LIMITED WARRANTY H WAIVER OF OTHER WARRANTIES THE EXPRESS WARRANTIES SET FORTH IN THIS LIMITED WARRANTY ARE IN LIEU OF AND EXCLUDE ANY AND ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE Some states do not permit the disclaimer of implied warranties Therefore the above disclaimer of implied warranties may not apply to certain purchasers I Procedure for Warranty Performance If the product fails to perform to LD s specifications the Buyer must provide LD with the applicable model and serial numbers the date of purchase and the nature of the problem J ADDITIONAL EXCLUSIONS FROM THIS LIMITED WARRANTY NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN THIS LIMITED WARRANTY THIS LIMITED WARRANTY DOES NOT COVER ANY OF THE FOLLOWING 1 EQUIPMENT THAT HAS BEEN ABUSED DAMAGED USED BEYOND RATED CAPACITY OR REPAIRED BY PERSONS OTHER THAN AUTHORIZED SERVICE PERSONNEL D 2 Model 720 User Manual June 7 2005 2 DAMAGE CAUSED ACTS OF GOD THAT INCLUDE BUT ARE NOT LIMITED TO HAILSTORMS WINDSTORMS HURRICANES TORNADOES SANDSTORMS LIGHTNING FLOODS AND EARTHQUAKES 3 DAMAGE UNDER CONDITIONS CAUSED BY FIRE OR ACCIDENT BY ABUSE OR BY NEGLIGENCE OF THE USER OR ANY OTHER
57. PERSON OTHER THAN LD BY IMPROPER INSTALLATION BY MISUSE BY INCORRECT OPERATION BY NORMAL WEAR AND TEAR BY IMPROPER ADJUSTMENT OR ALTERATION BY ALTERATIONS NOT COMPLETED BY AUTHORIZED SERVICE PERSONNEL OR BY FAILURE OF PRODUCTS PARTS FROM SUCH ALTERATIONS 4 COSTS OF REPAIRING DAMAGE CAUSED BY POOR OR IMPROPER MAINTENANCE OR UNAUTHORIZED REPAIR S COSTS OF MODIFYING THE PRODUCT IN ANY WAY ONCE DELIVERED TO THE BUYER EVEN IF SUCH MODIFICATIONS WERE ADDED AS A PRODUCTION CHANGE ON OTHER PRODUCTS MADE AFTER THE BUYER S PRODUCT WAS BUILT Authority to Alter This Limited Warranty No agent representative distributor or authorized dealer of LD has any authority to alter the terms of this Limited Warranty in any way This Limited Warranty may be altered only in a writing signed by an authorized officer of LD June 7 2005 Model 720 User Manual D 3 0 4 Model 720 User Manual June 7 2005 Index A AC output specifications 7 American National Standards Institute s eese bein eroe 1 4 ANSI standards A 10 B Battery directions for checking 2 9 internal life 0 1 16 Rates nein 8 7 C Calendar real time cocooccnccnonncconnnonnconnnonnnonnnocnnoss A 9 Calibration 1 5 8 11 C 1 2 Character 1
58. Press the v to item 75 Into Period Press and the numeric values for the interval period desired and then press Enter hh mm Press the v toIntv Time Sync item 76 for these choices Yes No Press the toitem 77 Intv Save L s The Choices are Yes No 6 7 05 Yes This option will cause the Model 720 to automatically stop at the end of each interval allowing the precise timing of a series of manual measurements To start a new mea surement the key must be pushed No This mode must be off for all automated measurements It is rec ommended that INTV Time Sync be 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 Lmax Peak and UWPK and the level setting measurements INTV a gives time interval number and date NTV b gives duration and interval number INTV c gives SEL and Leg 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 g gives statistical informa tion h is not used in the 720 6 7 05 Step 7 Press the d to item 79 Into Auto Stop The choices are Yes No Step8 To view Interval Histories after a measure ment has been taken press i A screen similar to the one below will appear Step 9 Examine the data available in each INTV Pre
59. R 164 _TAKT5 TAKT 5 nnn n dB R 165 _PsByTim PassBy Time of Occurance ddmmmyy hh mm ss R 166 _PsByDur PassBy Event Duration hh mm ss mm ss ss 6 7 05 167 _PsByMax PassBy Lmax nnn n R 168 PsByLeq PassBy Leq nnn n R 169 PsBySel PassBy SEL nnn n R 170 RevNumSL SLM Firware Rev amp Rev Date n nnn ddmmmyyyy M Other Read Commands Other read commands are macro commands that send multiple variables so multiple data can be retrieved from the 720 with one command Other com mands O 1 O 2 and O 4 are preprogrammed macros while O 3 is a user defined macro which is pro grammed by the Group command Code Description Response O 1 Read SLM data nnn n nnn n nnn n nnn n CR LF 4 SPL 11 TWA 17 Lmin 21 Lmax lt CR gt lt LF gt O2 Read Wind Data nnn n ccc nnn n nnn n ccc lt CR gt lt LF gt Read Group variables lt as programmed gt programmed by the group programming command G n r 1 n lt SOH gt lt HIGH_COUNT gt lt LOW_COUNT gt lt data gt lt CHKSM gt lt CR gt lt LF gt 04 Read 814 S LCD Display bit There are 1024 bytes data 8 lines of 128 bytes each mapped binary format Bits in each byte represent a verticle column of 8 pixels with the Isb on top Group Read Programming The group command permits the programming of a user defined macro with up to eight 8 Read variab
60. SHIFT and CED Step9 Press Enter Reset is complete and the instrument will return to the calibration mode Step 10 To leave the calibration mode press Cancel Calibration 3 3 Model 720 User Manual 6 7 05 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 By entering numbers assigned to each parameter the numbers are located above the keys on the key pad and are discussed later in the chapter e By scrolling up or down using the or v keys Byusing any white or blue function keys Follow these steps to access the parameters using numeric values A complete list of parameters and Step 1 With the Model 720 on press and the their assigned numbers is found in following screen appears Chapter 8 6 7 05 Quick Start 4 1 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 number will remove any prior parameter set tings The third way to access Current Time paramete
61. The letter A is on the S field Press SHIFT again f The keys are in the 2 field Press SHIFT twice to access the 2 field 5 To Clear the field press SHIFT twice to access the 2 chart and press the Clear key h 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 the v to go to the next field the second line Press and select the appropriate chart by pressing GHIFT 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 process Quick Start 4 5 The first and fourth lines will appear Step 9 The fourth line is for the Measurement Title on screen when the Model 720 is Press the v key turned on Step 10 To exit the setup mode press Cancel Setting Time Date and Day parameters Once you have set the parameters you can now enter the correct time and date The Model 720 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 follows The current time is displayed If itis Step 1 With the Model 720 on press SHIFT 155 incorrect enter the correct time Step 2 Press the key and use the numeric keys to enter correct time and then press Enter The current date will appear If itis Step 3 The Cu
62. You may press and make your selec tion with M and then press Enter Step 7 Press toitem 83 Hist Period 0 255 units Model 720 User Manual 6 7 05 These options select the history period length as determined by the 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 give 1800 seconds or 30 minutes for each Leg history period A period of 2 and a unit of 1 32 second would result in a history stored every 1 16 second Setting Item 83 to 0 is equivalent to setting 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 720 provides an ampli tude distribution that can be read on the display If the resolution is not satisfactory a different one may be selected and the amplitude distribu tion re displayed or printed This is possible because all data is stored to the nearest 1 8 dB 6 7 05 to select the value Step 8 Use the Modify and gt you want for this field Step9 Press the to item 85 Hist Base The set ting range is 0 255 dB Step 10 To enter a value press the value Enter Step 11 Pre
63. a C 7 Frequency Weightings specifications 1 4 Histogram Index 1 variables uta ld B 30 Histogram 21 History command Soe aee oreken re B 4 COCO AS i sdb em deines ois B 25 Hysteresis 8 14 I O Error Checking 23 INTEL fae enne tetti ortis 8 7 International Electrotechnical Commission aui cete tree io 1 4 Interval History sse 8 15 Interval Variables B 27 K keys functions of eee ides 2 2 L OQ eases scere de nee quet mre de 1 5 51 22 C 5 Level C 9 Dept of C 5 LN Ln Statistical Levels 8 13 Statistical Levels 8 13 8 10 Messages error messages and warnings 32 Microphone guidelines sess C 9 what it measures C 10 microphone reference number 1 11 Microphones capacitor eieiei eia aeee C 10 i sime C 10 C 10 Mode 5 Model 720 Index 2 Block Diagram 1 9 Components sese 1 7 Features x one pecie 1 4 Introduction eee 1 1 Keypad A tete 2 2 optional 1 12 Screen
64. a reset and C 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 R5 _O RTIME OverAll Runtime hhhhh mm 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 R 10 _O XR Overall Exchange Rate Text CCCCC R 11 C TWA Current TWA Time Wght Avg nnn n dB R 12 _C XR Current Exchange Rate Text ccccc B 6 Model 720 User Manual 6 7 05 R13 _O SEL Overall SEL nnn n dB R 14 _C SEL Current SEL nnn n dB R15 _O LMIN OverAll Minimum Level nnn n dB R 16 _O TMIN OverAll Lmin Date and Time ddmmmyy hh mm ss R17 _C LMIN Current Minimum Level nnn n dB R 18 _C TMIN Current Lmin Date and Time ddmmmyy hh mm ss R19 _O LMAX OverAll Maximum Level nnn n dB R 20 _O TMAX OverAll Lmax Date and Time ddmmmyy hh mm ss R21 _C LMAX Current Maximum Level nnn n dB R 22 _C TMAX Current Lmax Date and Time ddmmmyy hh mm ss R 23 _O LPEAK OverAll Peak Level nnn n dB R 24 _O TPEAK OverAll Lpeak Date and Time ddmmmyy hh mm ss R25 _C LPEAK Current Peak Leve
65. acknowledge i e Set 8 Thu will set day of week to Thursday Q uery parameter number option flags parameter value 6 7 05 3 Query 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 rec variable value E xceedance variable number time hist num variable value I nterval variable number relative rec variable value variable number relative rec 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 B 4 Model 720 User Manual 6 7 05 Mode Commands Format for the Mode Commands is Command Description M 1 Power On clear error message list and reset display functions to windows M2 Power Off M3 Run 4 Stop M5 View M6 Mark M7 Reset Current Data use S1 1 for Reset All M8 Reset Histories Only M 9 1 High Resolution Levels to I O channel only Inc
66. agram After taking a reading with Passby enabled you may wish to examine the Passby events You may also look at this while the instrument is running To do this fol low this step If PSBY appears in the screen it Step1 Press Exceedance which is now means you are in the Max PassBy Passby and using the a or 3 keys data screen Hit U 1 to get into the scroll through the events Use the 4 or Exceedance PassBy screen keys to look at information about this event Five screens are available here by using the r key giving time and date of the occurrence duration and Leg comparisons a EXCD a Time PassBy record and date b EXCD b Duration and record number of PassBy event c EXCD c SEL and Leg of PassBy event 7 12 Model 720 User Manual 6 7 05 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 Occurrence Time happened half way into the event and so forth The Single Highest Passby event is accessed by pressing U and 1 while in the EXCD Mode Overload 6 7 05 d EXCD d Max RMS level and Symmetry of PassBy record e EXCD e Peak PassBy level and UWPK of PassBy record Step 2 To examine the Maximum PassBy of all those collected press HIF andthe 4 key Use the 4 and keys to acces
67. ance of an electrical circuit and thereby to create a signal For high sensitivity this device has a voltage applied across the diaphragm from an internal source Electret A microphone that uses the motion of a thin dia phragm caused by the sound to change the capacitance of an electrical circuit and thereby to create a signal The voltage across the diaphragm 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 relatively 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 essentially flat frequency response for sound waves imping ing on the microphone from all directions What a microphone measures A microphone detects more than just sound The motion of a microphone diaphragm is in 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 raindrop 2 those caused
68. apter 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 t capabilities by looking at the parameter fields The Timer parameters 21 27 begin Step 1 Turn the Model 720 on press followed with this screen parameter 21 by SHIFD and P The following display will appear 6 7 05 Timed Measurement 6 1 Block Run Time 1 on Run Date to 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 Timel and Run Time 2 to Stop Time 2 each day from Run Date to Stop Date If the date is incorrect simply press m and enter the correct data then press e 6 2 Step 2 Press to access the cursor in brackets With the brackets flashing use the 0 to select one of four possibilities Off Block 1 Day or 2 Day 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 do this choose 2 Day and press Enter Step 4 To continue press the v to access the next parameter screen To continue our example we want to start 26 Septem ber 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 09 26 96 Press Enter The new Tim
69. at a time Step 2 When the arrow keys are used in conjunc tion with the Shift key the Model 720 will take you to the top or bottom of the parameters list Press SHIFT to move to the bottom of the parameter list Model 720 User Manual 6 7 05 The Model 720 moves you to the RMS detector parameters You are now at the beginning of the Exceedance parameters item 61 Step 3 Press the key Step 4 Press the SHIFT Press Enter NOTE Numbers are entered at the current cursor position Enter leading zeros if necessary keys and then 6 1 Changing Parameters Enter Modify This one has rounded brackets that mean this is an entry parameter Type the number or character desired 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 numerical and alpha entry see chapter 4 6 7 05 Parameters may consist of numeri33cal values charac ter fields or selected choices Numerical or character fields are shown between parentheses Another parameter type is the template entry parame ter These prompt for specific data entry For example For both types follow these simple steps Step 1 Press Step 2 Enter a value from the numerical keypad Use the key for alphabetical input Step 3 Confirm any change with Enter Step 4 Cancel any change by pressing before E
70. ate against higher frequencies High Pass A frequency filter that permits signals to pass through that have frequencies above a certain fixed fre quency called a cutoff 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 fre quency called a lower cutoff frequency and below a certain fixed frequency called an upper cutoff frequency The differ ence between the two cutoff frequencies is called the band width 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 is a doubling of frequency so the upper cutoff fre quency 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 vibra tion measurements The frequency chosen to describe the band is that of the center frequency Note table in Frequency 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 more
71. by the movement of air over the diaphragm such as environmental wind or blowing 3 those caused by vibration of the micro phone housing and 4 those caused by strong electrostatic fields Rules 1 Do not permit any solid or liquid to touch the microphone diaphragm 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 vibra tion particularly in direction at right angles to the plane of the diaphragm 4 Keep microphones away from strong electrical fields Model 720 User Manual 6 7 05 6 7 05 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 microphone diaphragm a simple constant the dia phragm area relates the two but if the pressure varies across the diaphragm the relationship 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 speci fied by the manufacturer to increase the frequency response choose smaller microphones 2
72. cable end 4 conductor shielded e CBL035 Connects Model 720 and customer sup plied external battery CBL038 Connects Model 720 to battery and RS232 port of most laptop computers CBLO77 extension cable or similar recommended if longer length required Model 720 User Manual 6 7 05 6 7 05 CBL042 AC DC output of the Model 720 to RCA BNC connectors INT002 RS 232 cable level converter for data trans fer to PC Requires 9 V battery or external AC power supply P5001 included Note that external supply will also power the Model 720 PSA001 AC DC power adapter 115 Vac to 9 Vdc 50 60 Hz for use with INTO002 CCS002 Custom hard shell airtight watertight case 13 1 2 X 12 7 8 X 6 in CBLO040 Similar to INT002 but allows one to daisy chain an additional Model 720 P5002 AC DC power adapter 220 Vac to 9Vdc 50 60 Hz for use with INT002 EPS012 Weatherproof fiberglass case with custom cut foam interior and desiccant Sealed signal cable feedthrough Features lock hasp and may be chained through handle for security EPS013 Same as EPS012 but with 8 Ah 12 Volt rechargeable battery BATO004 Provides 1 week operation in normal conditions Includes CBL038 and battery charger Introduction 1 13 Note Figure 1 4 call Larson Davis for additional information on these and other accessories __ Rainhat with electrostatic actuator V wsoo1 WS005 Windscreen G O with birdspi
73. d Two year warranty see warranty statement on the copyright page at the front of this manual A layout of the Model 720 is shown below Model 720 User Manual 6 7 05 Microphone Windscreen LARSON DAVIS LCD Display MODEL 720 AC DC Out 7 8 9 TIME TIMER TAKT LDL Lea SEL TWA DOSE 4 5 6 CAL SLM LN 1 2 3 Nose Cone LOCK MEM LOG 20608 Cancel 0 Enter OFF STR RCL RESE ON PRINT SETUP R S TYPE 2 INTEGRATING SOUND LEVEL METER Keypad Serial Interface Port 6 7 05 Introduction Figure 0 1 Model 720 The Model 720 is a convenient hand held sound level meter with a simple user interface As can be seen the standard Model 720 includes the following Model PRM789 3 8 inch preamplifier The pream plifier cable may be looped inside the provided nose cone when the meter is used as a hand held A two line 32 character high contrast LCD dis play Keep clean and protect from con Model M1 3 8 inch prepolarized microphone The densing moisture and water Rain microphone is rugged and reliable but the Model droplets or other foreign matter on 720 should be kept in its protective case when not the diaphragm may alter the micro in use Avoid unnecessary shock Although an LeD phones s response Please use a microphone can survive being dropped it should windscreen whenever possible be handled with care A 20 key membrane keypad Model 720 precision ha
74. dB Leg 4dB gives L DOD 5dB gives LOSHA 6dB gives L Avg 68 Ex Min Duration 0 255 Exceedance must last at least this many seconds to be logged 162 Excd Trigger Level Bypass Bypass Enables a variable thresh old 8 14 Model 720 User Manual 6 7 05 Interval History 72 79 72 Prompt Intv Enable Entry No Yes Comment Interval report will be stored in memory if Yes is entered 73 Intv Exchange 3dB 4dB 5dB 6dB Used to calculate interval inte grated level Normally this is set to Leg 4 dB gives Lpop 5 dB LosHa Lavg 74 Intv Threshold 0 to 255 dB Levels above threshold are inte grated during each interval nor mally 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 1 minute up to 99 59 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 running at the start of each hour or minute depending on Intv duration 77 Intv Save Ln s No Yes Selects whether interval L s are stored The Ln s stored are those in effect items 55 60 at end of inter val 79 Intv Auto Stop No Ye
75. dee ete mes 2 8 System Diagram 1 9 Turning On 2 8 Model 720 Components 1 7 Model 820 Glossary App C 1 Specifications App A A 1 N Near Field dcOtstie ioannes E C 12 geometric sss C 12 glossatyi chiede C 12 Noise ambient C 12 Background C 12 compensate sss B 23 daily personal exposure C 3 dose D aie ania e C 13 13 POOR iaa a B 23 glossary cde C2 C 12 A A C 13 projected noise dose C 13 single event exposure level SENEL Lax C 13 irent C 13 Numeric Parameters B 16 Off directions for turning off 2 10 OSHA level TT C 13 Overload 7 13 Parameter iii a B 16 Chapter ou dada 8 1 Character 16 character 5 1195 13 indexed ute rete hei B 13 numeric eene B 13 B 16 GUE REA B 14 setting E 13 template cedem B 13 PassBy iii 7 11 Passby Diagram 7 12 Peak citas 5 3 8 16 Diti ae eee E e e B 2 Pin configurations eee B 2 Power connecting 1 15 1 15 to 1 16 internal 1 15 specification
76. dshaking protocol shaking Register Both Model 720 SW1 uses None Note To conserve power the Model 720 turns off the serial port after 255 sec of non use To keep unit on and connected an external power supply must be used 14 Output 1 Logic Off True takes it to 5 volts When set to RMS R Off DTR is DTR PEAK P R P INTV 1 Indication that Interval started and will stay on time set in R I parameter 15 P I R P I A D A Logic control including A are R A not applicable to the 720 P A R P A I A R I A P I A R P I A R S Run Stop 15 Output 1 Timer enter time There are 2 modes to the Logic Output Time now If the time is set to 5 sec or less it is assumed to be a minimum time and the out put will be asserted for a mini mum of the time selected If the time is programmed to be greater than 5 sec then the time is consid ered to be the maximum duration that the pulse should last and the output will be asserted for a mini mum of 5 sec and a maximum of the time programmed 8 8 Model 720 User Manual 6 7 05 20 Power Save Auto Off Manual Auto Off If in the Stop mode and Off Audio Off if no keys are pressed or com mands given for 12 min the Model 720 will turn off automati cally Manual Off The Model 720 will not turn off until the O key is pressed a computer Off com mand is given or the batteries become low Audio Off Not available on the Model 720 Timer 21 27 U T These
77. e The easiest way to estimate the memory usage is to work on a time basis such as one day Consider the fol lowing 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 Based on the options chosen calculate the number of bytes required for each record type Multiply by the number of records expected per day 9 2 Model 720 User Manual 6 7 05 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 720 see U M and this is the number of days the Model 720 can gather data As an example let s assume a job requires monitoring the noise made by trucks coming and going from a fac tory 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 residential property and that there seems to be a truck passing the site every 3 min utes 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
78. e field However you do not have to recalibrate the Model 720 when you change the settings Please note that if you use a calibrator which uses another frequency some corrections may be required depending on the weighting The output level and the frequency of your calibrator should be listed on its label Use this level with specific environmental and weighting corrections to calibrate the Model 720 level Calibration 3 1 3 2 Calibrating the Model 720 The LarsoneDavis Model CAL150 calibrator outputs 114 dB or 94 dB 20 uPa Note that the Model 720 automatically uses the C weighting while calibrating This ensures a cor rect reading at typical calibration frequencies of 250 Hz to 1 kHz Refer to the specific instructions accompanying your calibrator for accomplishing this step To begin the calibration process check or insert the new calibration level given in parameter 35 Step 1 To do this press Modify and 5 then Enter The following screen will appear Step 2 Press then enter the SPL value of your calibrator if other than 114 0 includ ing any corrections for pressure etc Step 3 The next setup item allows entry of the cali brator serial number for record keeping pur poses Press the or 5 Modify 3 and 6 and Press to change the serial number enter the correct numbers and press Enter Step 4 Seat the microphone fully in the calibrator cavity If
79. e influence of other sources by measuring the 11 Near Field Noise C 12 background 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 wave length varies with frequency See the definition of Wave length 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 rapidly wind noise since most of the pressure changes are to move the air and very little of it compresses the air to create sound Persons 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 s
80. e steps Step 1 Turn the Model 720 on and press The following display will appear briefly and then scroll automatically through several options 6 7 05 Printing a Report 10 1 Items 89 112 allow you to select the reports which are to be printed and how the output data are to be config ured Items 89 112 are copied sequentially into items 177 200 for printing tai lored reports and may be edited directly for one printing and then they will revert to settings entered in parameters 89 112 Printing Reports 10 2 Step 2 To tailor your report and select the printer type and options press 7 and the following screen will appear N There are several options here which include HPJet HPLzr ASCII Epson IBM Step 3 You can change the printer selection by press ing the key and then f to the printer you will use and press Enter Step 4 Pressthe Y key to the next display item 89 duplicated here as item 177 the begin ning of the parameters that manage printouts Step 5 Scroll through these parameters with the v key and make your selections Press to access the appropriate choice and press Enter NOTE For a complete list of Print Options see Chapter 8 Printing reports is easy as connecting your Model 720 to a printer and pressing a key Using the CBL033 serial printer cable connect your serial printer to the Model 820 at its bottom port Let s look at the print opt
81. ected via parameter 42 UWPK Weighting therefore it can be set independent of the RMS Detec tor frequency weighting The Unweighted Peak Detec tor s typical FLAT frequency response is shown in the table below 3 The AC Output frequency weighting is selected via parameter 41 AC Out Weighting It can be set to Flat weighting or it can be set to match the RMS Detec tor frequency weighting The AC output s FLAT fre quency response is shown in the table below Unweighted Peak FLAT Frequency Response Nominal Unweighted Peak Nominal Fre Unweighted Peak Nominal Unweighted Peak Frequency Hz FLAT quency Hz FLAT Frequency Hz FLAT 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 4 Model 720 User Manual 6 7 05 Unweighted Peak FLAT Frequency Response 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 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 1
82. ed by parameters 72 79 MEM Memory use in percent bytes free and total byte available are provided as well as a count of all of the History Records stored in memory HIST The Time History function is a record of short interval L reading and optionally a Peak UWPK or read ing The interval can vary from 1 second to 255 sec History 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 taking process of the Model 720 CAL Calibration information and con trol Initially in the CAL a display the current calibration offset is displayed with a flashing prompt to press either the UP arrow key to check the calibration or press the d key to change the calibration SLM The Sound Level Meter function displays the current Sound Pressure Level SPL while the instrument is in the Run Mode or the SPL at the instant it was last stopped Model 720 User Manual 6 7 05 Functions Lmax The maximum SPL or is the largest sampled SPL for the overall mea surement period displayed with the date and time of its occurrence Two addi tional screens accessed by pressing the left or right arrows show the number of times the SPL exceeded two fixed levels Luin The minimum SPL or Lmin is the lowest sampled SPL for the overall mea surement K PEAK The highest weighted Peak Detec tor output level Lok Date and time of t
83. eedances were 27 total Intervals were 3 and 1 Daily Histo ries Should any of four let ters OVLD flash in the place of the figure in the upper right this would indicate there was an Over load during the reading see chapter 7 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 num ber of RUN STOP s made and CL is the number of calibration check records Step 1 Press SHIFT and 8 A screen similar to the following will appear Step 2 Press the b key to access the next screen Step 3 The third screen gives additional information Press the gt key to examine this screen Stopping the Measurement Press to stop the measurement The stick figure will resume the resting position To view any of the previous measurement data simply press the appro priate key and the information will appear 6 7 05 Performing a Measurement Reading the Data 5 13 5 14 Model 720 User Manual 6 7 05 CHAPTER Timed Measurement The ability to take a measurement at a specific time and date is one of the unique qualities of the Model 720 This feature allows you to take unattended mea surements Accessed through the TIMER key this flex ible system has modes to permit 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 ch
84. emory reset Cur All 33 Lock ON Key No Yes 34 Lock I O No Yes 40 Model 720 User Marval 065 Calibration 35 36 UC No Prompt Entry Comment 35 CAL Level 114 00 Enter the sound pressure level of 0 255 dB your calibrator 36 Calibrator S N to 8 char Calibrator serial no will be printed Sound Level Meter 39 50 c These parameters define the sound level meter charac teristics Most changes will require a SHIFT if memory holds previous data No Prompt Entry Comment 39 Detector Slow Fast Impl Slow exponential avg 1 second constant Fast exponential avg 1 8 second constant Impl impulse response 40 Frequency Weight A A16 C C16 A and C weightings meet Type 2 ing specifications Note A16 and C16 not applicable to the Model 720 41 AC Out Weighting Flat Wght F 20 20 Flat Level with 20 dB gain W 420 W 20 Weighted with 20 dB gain 42 Unweighted Peak Flat C 44 Reference Level 0 to 255 dB measured level reference level relative level used in some func tions 45 Current 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 inte Threshold 1 grated into currant TWA or Dose readings For OSHA use 80 dB 6 7 05 Parameters 8 11 47 Current
85. ensity 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 is 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 emotional overtones associated with the word noise Some sound metrics 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 spe cific time period It is expressed in Pascals squared seconds SE T where pa is the sound pressure and T Ty is the Measure ment 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 1 25 Sound Exposure Level SEL Lgr The total sound energy in a specific time period The C 14 equation for it is Model 720
86. ents the sound pressure 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 expo nential 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 multiplied by 10 When the value is not a even multiple of ten the exponent is more com plicated 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 10 Exponent Ration of Value to Reference of Ratio 1 10 0 10 10 10 100 10 20 200 107 23 1000 10 30 10000 10 40 100000 10 50 1000000 10 60 The definition of decibel is intended for power like quanti ties W Sometimes power is represented by the square of a measured quantity and this results in a different form of the equation See Sound Pressure Level Ls l0Log y wW Wo 0 The value of the item in the table is not the value of the quan tity itself but the ratio of that quantity to a reference quan tity So for every level in decibels there must be a reference quantity When the quantity equals the reference quantity Model 720 User Manual 6 7 05 the level is zero To keep the values above
87. ep 1 Press SHIFT Step2 The x keys will scroll through the two RAM registers For example press v twice The RAM register 1 is empty Step 3 To store the current setup to the displayed RAM 1 register press Enter Parameters 8 5 Recalling a Setup registers 0 and 1 and EEPROM register will recall previ ously stored calibration data STORE saves the CAL data so that the calibration for may be stored and recalled as desired Memory must be reset before a recall of setup parame ters can be accomplished Step 1 Inthe stop mode press SHIFD C Enter to reset memory Then press SHIFT Step 2 The EEPROM is again the default Use r and d to scroll through the two RAM registers or u to recall the programmed ROM setups Note that the first ROM is the default Model 720 Setup Parameters 8 6 Setup parameters of the Model 720 are listed below Modifying 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 corrup tion of the overall noise data Parameters are listed below in logical groups with their number 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 720 s big brother Model 720 User Manual
88. ep 2 With the instrument in RUN mode press 5 The current sound pressure level is dis played Step 3 An additional six screens are available from this display Pressthe v key to access the first These values may be checked at any time while the measurement is being taken or final readings after the measurement has been completed Be careful not to bump or drop the instrument as the results of the read ing will be affected Model 720 User Manual 6 7 05 The Peak and Unweighted Peak are displayed here Note that the Model 720 is still taking a measurement here however in the stop or pause mode the Model 720 continues to display the detected values on the upper right hand side of the screen The numbers on the left are the high est during the measurement and the numbers on the right are the current Peak and Unweighted Peak The L4 values are shown here to be 85 5 dB C weighted the measure ment ran for 3 minutes plus Should an Overload occur one of four letters OVLD would flash alternately with the stick figure in the upper right corner see Chapter 7 The SEL level using 3 dB exchange rate is 109 1 dB and the duration of the measurement is given The Alarm can be set to begin a mea surement at a designated time The 22 22 here indicates the next mea surement has not been chosen The current internal temperature as mea sured by the Model 720 is shown in the lower port
89. er Run Date is now 26 Sep 1996 Step 6 To access Timer Stop press the x A Previ ously entered date will appear Step 7 To change the date press and enter the 5 day ending date i e October 1 i e 01 10 96 and the following display will appear Model 720 User Manual 6 7 05 8 Notice that military time is used 0 01 24 00 to avoid confusion with A M to P M Step 11 Step 12 6 7 05 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 Our start up time is 8 30 A M so press 08 30 Enter and the display should look like this Press the x to Stop Time 1 Press to enter the numbers 12 00 and then press Step 10 Press the v to Run Time 2 Press to enter 13 00 our afternoon start time Press Enter Press the x to Stop Time 2 Press to enter 16 30 Enter To check your Timer setup press Cancel This will return you to the main screen Press SHIFT and the following screen should appear Timed Measurement 6 3 Step 13 If you press amp key it will give you the morning time run If you press the 0 again it will give you the afternoon time run settings The Model 720 can now be turned off by pressing and placed in the test area Make sure to check the bat tery Chapter 2 or connect to externa
90. erial Port Line Noisy 161 Serial Port Over Run 162 Wait for Stabilization 163 Power Turned Off 6 7 05 B 33 164 Time Date Not Set 165 Printer Already BUSY 166 Lithium Battery Low 167 Timer ON Pending 168 External Power Fail 169 Calibration Changed 170 I O Stack Overflow B 34 Model 720 User Manual 6 7 05 Glossary This appendix contains technical definitions of key acoustical and vibration terms commonly used with Larsone Davis instruments The reader is referred to American National Standards Institute document S1 1 1994 for additional definitions Specific use of the terms defined are in the main body of the text Allowed Exposure Time T 8 It is the allowed time of exposure to sound of a constant A weighted sound level given a chosen Criterion Level Crite rion Duration and Exchange Rate The equation for it is T T T Z c P OUO E Ey where L is the Criterion Level T is the Criterion Duration Q is the Exchange Rate K is the Exchange Rate Factor and Lavg is the Average Sound Level Example If L 90 T 8 3 and L 95 then C ES 5 656 5 hours and 39 minutes Tom zu o 100959007109 2095 90 3 Average Sound Level Layg 6 7 05 This means that if a person is in this area for 5 hours and 39 minutes he will have accumulated a Noise Dose of 100 Standard ANSI 12 1
91. etting PassBy eene 7 11 Overloadco NO 7 13 Parameters 8 1 Parameter Key Access 8 2 Entering and Exiting the Setup Menu 8 2 Locating Parameters ci enden eds 8 2 Changing Parameters Enter 8 3 Etror MesSage8 HON ON EH PEE P e eere 8 4 Learning to Store and Retrieve Setup Memory sss 8 4 Storing a Setups netto te en e Rete edant 8 5 Recalling Set p eese oerte RE Hee 8 6 Model 720 Setup 2 8 6 System 1 20 6 105 eee eerie det i eR e REIR erts 8 7 Tamer 21 22 U T i nti i teet tr er ii ipt indes 8 9 Lock 28 34 terme mre err 8 10 Calibration 35236 Uli ERR 8 11 Sound Level Meter 39 50 sss 8 11 Doses ESI E noia 8 12 LN Statistical Levels 55 58 B enne 8 13 Exceedance Levels 61 65 8 13 Exceedance History 66 68 162 8 14 Interval History 72 79 cnini P Re EH 8 15 Time History 80 87 eet eite ev nd eU M ideis 8 16 Print Options 89 112 s enne 8 17 Additional System Functions 159 162 8 19 Chapter 9 Memory Usage 9 1 Determine Storable Data dece 9 1 Estimating Memory Usage eene ener nne nenne nnn 9 2 Chapter 10 Printing a Report 10 1
92. f sound power It is also expressed by Sound Speed c attachment of the word decibel to the number The loga rithm is taken of the ratio of the actual sound power to a ref erence 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 ME Ilog yy W 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 20 05 4degC 273 m sec 49 03 degF 460 ft sec Spectrum Frequency Spectrum The amplitude of sound or vibration at various frequen Threshold Sound Level Lt C 18 cies It is given by a set of numbers that describe the ampli tude at each frequency 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 pro duces little or no Noise Dose accumulation and may be dis Model 720 User Manual 6 7 05 regarded It is used for hearing damage risk assessment Standard ANSI 51 25 Time Weighted Average Sound Level TWA Erwacrc It is the level of a constant sound Time Weighting Vibration Wavelength 1 6 7 05 over the Criterion Duration that wo
93. formation below You may be asked to give this information in any future communications you have with Larson Davis Inc Record of Serial Number and Purchase Date System 720 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 Lhis Manual mds 1 2 About This Chapter i ier RR enn enn 1 3 Formatting Conventions ener nennen 1 3 Eeat res accetto e n Re eon oet e bes 1 4 Model 720 Components esses eene enne nnne 1 6 Block Diagram iin sese e eec m eere er 1 9 Getting Started coa sie eee aiti I te as 1 11 Unpacking and Inspection essere 1 11 ACCESSO Siia oaia 1 12 Optional Equipment E RENS I eet 1 12 Battery Installation esee Ee des 1 15 Environmental Considerations essere 1 17 Overview to Model 720 2 1 Understanding the Model 720 Keypad sese 2 2 Getting to Know Screen Symbols sse 2 7 Understanding the M
94. g Reset B 10 An indicator has been added to the ON display on the top line of the 720 s display to show faults that were detected by Model 720 User Manual 6 7 05 the power on test procedure The R151 command will dis play the fault character to a computer R 152 _INRMS Internal RMS detector level nnn nn dB R 153 _INPEAK Internal PEAK detector level nnn nn dB R 154 _INUWPK Internal UwPk detector level nnn nn dB 155 _ Free Bytes in Keyboard Stack nnn 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 R 156 _BGTIM Background Leg Time hhhhh mm ss ss R 157 _CALSTAT Calibration Status lt lt UnStable gt gt R 158 _MEMSIZ Total number of bytes for histories nnnnnnn R 159 _MEMUSE Memory Available in percent nnn nn R 160 _O OVLD OVERALL OVERLOAD FLAG R 162 _O SE Overall Sound Exposure nnnnn n P H Sound Exposure E is calculated and displayed in pas cal 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 e 10 Leq 10 20uPa where E is the Exposure T is the elapsed time in hours and 20uPa is the reference sound pressure 20 micro pascal squared R 163 _ 3 nnn n dB
95. h the following equation 4 22 2 _ 0 A c where A is the wavelength c is the sound speed f is the fre quency in Hz and o 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 C 20 day is averaged over the entire year It is calculated as fol lows 365 1 Lyan l0log 3552 10 1 10 Model 720 User Manual 6 7 05 APPENDIX Warranty Customer Satisfaction A Total Customer Satisfaction Larson Davis Inc LD guarantees Total Customer Satisfaction If at any time you are not completely satisfied with any LD product LD will repair replace or exchange it at no charge except as otherwise provided in this Limited Warranty The employees of LD strive to provide superior unmatched customer service Should you find yourself dissatisfied with any LD product for any reason consult a LD Application engineer or local representative distributor to discuss your situation B Purchase Price Refund Limited Warranty LD warrants to the original purchaser the Buyer that unless otherwise expressly specified in writing by a LD officer all LD products shall be free of defects in material and workmanship for a period of two 2 years from date of original purchase In furtherance of LD s commitment to Total Customer Satisfaction LD will for a period of one 1 year from date of original purchase refund 100 of
96. he occurrence of the Lp is also shown The number of times the weighted peak level exceeds a programmed threshold is also counted and displayed b window The highest UnWeighted Peak Detector output level Lywpx The date and time of the occurrence of the Luwpk is also shown The number of times the weighted peak level exceeds a pro grammed threshold is also counted and displayed b window B The Ly values represent the SPL exceeded of the run time All values from 1 to 99 are available two of four are displayed at a time and can be changed even while running BATT This key gives the percentage of power remaining in the 9 V battery or external supply BATT b Gives Model 720 revision num ber and date 6 7 05 Overview to Model 720 2 5 Functions LEQ The Equivalent Level or Leg isa Time Weighted Average based on an exchange rate of 3dB true energy mea sure with no threshold TIME The date and time of last reset or measurement start are available from the Time a display The current date and time are shown with the Time b display SEL The Single Event Level or Sound Exposure 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 measure ment at a specific time and date is avail able thus permitting
97. ht 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 corner of the display indicating this panel is accessed 6 7 05 instrument s display will show the number of times the SHIFT key has been pressed by showing the let ter n and then 2 and 3 respectively for 0 to 3 presses Figure 0 3 2 Shift Level 2 Alpha Numeric Keyboard Quick Start This final panel is accessed by press ing the shift key three times The number 3 appears in the lower right corner of the display indicating this panel is accessed 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 let ters here by using the Alpha Char acter Keyboard Entry shown above The flashing n is replaced by S and will remain for five seconds At this time you may select any charac ter from the S table press that key and it will replace the letter at the cursor _ The cursor then moves to the next letter Use the gt keys to move the cursor without changing the letters The n is replaced by 2 for five sec onds Letters from the 2 panel are available for entry
98. ield the sources have all merged into one so that measurements made even further away will be no different See the defini tion 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 exten sive 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 Model 720 User Manual 6 7 05 Frequency Band Pass Filter Frequency Filter Weighted 6 7 05 in cycles per second and the value has the unit symbol Hz Hertz added and the letter f is used for a universal descrip tor 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 w 2Mf The part of certain sound level meters that divides the fre quency 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 fre quency called a cutoff frequency It is used to discrimin
99. in each field History Functions 7 9 Must be Level Passby treated later 7 10 End of Start of Exceedance Exceedance Figure 0 1 Exceedance diagram The diagram above is an example of an exceedance with markings of explanation It should be noted here that additional parameter set tings have been added out of numerical sequence to satisfy additional needs found in the field These will be treated now e 162 Excd Trigger Level PassBy Occurrence Time T if set to Start Occurrence Time T nax if set to Max T max start try 100 Symmetry Duration Lmax must be gt RMS Level 1 Only events that are longer than the minimum dura tion set and having Lmax greater than the RMS Exceed ance 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 buffer is used to create this Model 720 User Manual 6 7 05 Five screens are available Time and Date and the Exceedance number as seen in the screen to the left Duration Le comparisons Lingy Symmetry Peak and UWPK Setting PassBy Functions When the Exceedance History and Passby parameter 66 and 162 is enabled a Passby record will be cre ated whenever a delta 10dB event is detected See Figure 7 2 6 7 05 function The max duration of a passby event is 128 samples which is
100. in the following order Type 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 Measurements AC and DC Outputs Reference Frequency Stabilization Time Microphone Electrical Impedance Functions Measured Data Storage Reference Direction A 2 Data Communications Digital Display Digital Display Resolution Display Bargraph Real time Clock Calendar Run time Clock Typical Noise Floors e Standards Met Power Supply Dimensions Weight with Microphone Preampli fier and Battery The Larsone Davis Model 720 with attached PRM 828 preamp and Model 2541 microphone is a combination Type 2 precision integrating sound level meter and sta tistical data logger The reference direction is perpendicular to the plane of the microphone diaphragm when using a free field microphone in a free field The microphone should be pointed directly at the source When using a random incident microphone in a free field the microphone should be pointed 80 degrees off axis of the source of the sound When in a random sound field a random incident microphone may be pointed in any direction Model 720 User Manual 6 7 05 Measurement Ranges RMS Detector Dynamic Range gt 110 0 dB Prima
101. ion of the screen Step 4 Press the Y key again for the second screen In this example the measurement has been stopped Notice the figure is at rest Step 5 Pressthe v key for the third screen Step 6 Pressthe v key for the fourth screen Step 7 The next screen addresses the Alarm time and current temperature Press the Y key the fifth screen will appear 6 7 05 Performing a Measurement Reading the Data 5 3 The Model 720 has been pro grammed to save power whenever it can Each time input is made this the internal timer will start at 100 and count downward If not programmed to do otherwise the Model 720 will turn itself off when this screen reaches 0 just over two minutes Slow exponential avg 1 sec con stant 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 2 standards for accuracy A16 C16 and Flat do not apply to the Model 720 5 4 Step 8 The property controlling the final screen in this series is built into the Model 812 to con serve power Press the v
102. ions again Model 720 User Manual 6 7 05 You will notice that the scroll is quite rapid To slow it down so you can study the options use the u or d keys and the display will remain for five seconds before returning to automatic scroll A following the key name indi cates the option function will be invoked after selecting that key oth erwise the particular report will be printed immediately 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 d key will access item 89 of the Print out Parameters This option allows you to tailor your own report changing the settings of parameter items 89 112 The brackets contain the command that will produce the Exceedance Report i e EXCD 6 7 05 Step 1 Turn the Model 720 on and press Far The display will begin to scroll through the vari ous print options available Here are some of the screens Step 2 Pressthe v key until you find the Exceed ance History report screen Step 3 To generate an Exceedance Report press the key Assuming your reading has Exceed ances the report will contain all recorded occurrences during the test period Printing a Report 10 3 10 4 Model 720 User Manual 6 7 05 6 7 05 CHAPTER Specifications This Appendix contains the specifications for the Model 720
103. is prevents multiple exceedance for a single event if level fluctuates about the threshold Yes would insure 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 5 dB gives LOSHA 6 dB gives L Avg This parameter sets the minimum duration in seconds of exceedance records 6 7 05 e 65 Excd Hysteresis 0 9 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 are indicated on the printout respec tively This count has nothing to do with duration but only indicates the number of times the level went above the various exceedance levels Ihe Exceedance History parameters items 66 68 allow you to select and define what data are to be saved in memory during an exceedance Each exceedance indicates the time it started dura tions symmetry Leg SEL Lmay Peak and Time His tory if desired Press and from the previous field or press Modify 66 and Enter to access item 66 RCL SETUP Step 1 Here is a brief explanation of each parameter e 66 Excd Enable Yes No 67 Excd Exchange 3dB 4dB 5dB 6dB e 68 Ex Min Duration 0 255 Use the 3 key to scroll through the fields Use the Modify gt and keys to make any changes desired with
104. item 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 Step 3 If you wish to change this level press enter the desired dB numerically and press Enter 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 4 Press the v key item 47 Press if you wish to keep the 90 dB level or press enter the desired dB numerically and press Enter The Current Dose is often used as a second Dose mea surement The collected data is available on the print out Performing a Measurement Reading the Data 5 9 Changes can be made in any display by pressing m entering desired val ues and pressing e The overall criterion level set in item 50 and the dose hours set in item 51 determine what is 100 dose OSHA criterion is 90 dB Threshold is 80 dB Exchange Rate is 5 dB and the Full Dose hours Criterion 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 5 10 The Overall Dose parameters have the same available settings as the current settings and are accessed in the same way Step 5 To access items 48 50 Overall Exchange Rate Overall Threshold Overall Criterion press the v key Full Dose Hours item 51 has a range of 0 to 99 hours but is normally set to an 8 hou
105. kes a 1 2 inch Microphone 5012 Environmental Case I JADPO11 PRM2101 j A 720 SYSTEM 2106 7 8 PRM828 EPS013 Environmental Case w Battery Note Those items marked with are standard included accessories T Software SWW SLM UTIL SWW SLM LINK EXCXXX SWW ENV 20 Max SWW REM SWW NMS 800458 AC Out black neo DC Out red Larson SWW ACS CBLO09 020 820 OPTO1 required Davis ccsoog Soft Case Battery powers 2101 heater and EA INTOO2 12 4 Conductor CBLO34 6 Shielded 4 1 PSAoo1 Desktop Computer TonextSLM 42 Battery to CBLO35 4 power 720 PsAoo1 alligator clips CBL116 1 5 CBLO77_ 6 optional 4 PSAO05 AC DC Adaptor mi 2 I c1 Laptop Computer Battery 7 CBLO33 6 CBL116 1 5 CBLO77 6 optional Serial Printer Figure 0 4 720 System Diagram Battery Installation To insert the 9 volt battery in the Model 820 remove the battery cover at the lower left side of the instru ment by sliding it out as shown in Figure 0 5 1 14 Model 720 User Manual 6 7 05 Figure 0 5 Remove Battery Figure 0 6 Inserting Battery 6 7 05 With the battery door removed drop the battery into the opening in the case as shown in Figure 0 6
106. l nnn n dB R 26 _C TPEAK Current Date and Time ddmmmyy hh mm ss R 27 _O LUWPK OverAll UWPk Level nnn n dB R 28 _ OverAll Luwpk Date and Time ddmmmyy hh mm ss R29 _C LUWPK Current UWPk Level nnn n dB R 30 _C TUWPK Current Luwpk Date and Time ddmmmyy hh mm ss R 31 _RMSCNT OverAll RMS Exceedances 1 nnnnn R32 RMSCNT2 OverAll RMS Exceedances 2 nnnnn R 33 _ OverAll Peak Exceedances nnnnn R34 _UWPKCNT OverAll UWPk Exceedances nnnnn 35 _OVLDCNT Overloads nnnnn R 36 PSEONT Number of PAUSES nnnnn R37 PTIME PAUSE Time OFF not inc hhhhh mm ss R 38 _LN1 En 1 nnn n dB R 39 _LN2 Ln 2 nnn n dB 6 7 05 40 _LN3 Ln 3 nnn n dB R 41 _LN4 Ln 4 nnn n dB R 44 _O DOSE Overall Dose nnnnn n96 R 45 C DOSE Current Dose nnnnn n R 46 _O PROJ Overall Projected Dose nnnnn n R 47 C PROJ Current Projected Dose nnnnn n96 R 48 _LDLDOSE LDL Dose nnnnn n 49 _LDLPROJ LDL Projected Dose nnnnn n R 50 _LDLLINT LDL Lint nnn n dB R 51 _LDLSEL LDL SEL nnn n dB R 52 _LDLXR LDL Exchange Rate Text ccccc 53 _LDLVALID LDL Valid display see note below cccccc NOTE An LDL Logged Data Logic recalculation can be started with a R 53 Command When the Model 720 is RUNNING the Valid condition will remain in effect for 1 second The R 53 Com mand provides three responses LDL Valid Calculating and LDL Invalid R 54 RELLV
107. l power Also consider the safety of the instrument during the test period Finally verify that the current time and date are set correctly in the internal clock The following section covers setting the time and date The Model 720 will turn itself on and begin mea surement at the appropriate time Using the Time Key Functions Current time day and day of week are controlled by parameter 6 8 This screen displays the time and date the current or last measurement began 6 4 In Chapter 5 we learned to take a measurement and examine some of the data gathered during that read ing The TIME key functions as a record of when the last measurement started Two screens are available in this function Step 1 PressGHIFD and to access this infor mation Model 720 User Manual 6 7 05 The second display shows the cur Step2 Press the v key to access the second screen rent date day and time Step 3 Press Cancel to return to the main screen Setting the Password Lock to Protect Settings The Model 720 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 Y or from the main screen press 28 Enter You can also press A Eg Refer to Chapter 4 to review entering Step2 Press and enter your personal combi numbers or letters by using the nation of numbers or letters from 1 8 charac SHI
108. les The macro is executed with the GO or O ther 3 com mands which returns the list of defined read variables Use the following command syntax to program each desired read variable and its position in the macro Syntax Response B 12 Model 720 User Manual 6 7 05 G roup n var_no lt cr gt lt lf gt Example G1 4 lt cr gt assigns the current SPL to the first group option Example G2 15 lt cr gt assigns Lmin to the second option Example G3 19 lt cr gt assigns Lmax to the third option Example G4 0 lt cr gt terminates group command programming Where n is from 1 to 8 indicating the macro position and var_no is the number of the R variable associ ated with the position Use a var_no of 0 to define the last position when less than eight are desired After programming this group read list the response to is 59 5 38 6 102 2 the SPL Linin and Lmax respec tively The Group command can be programmed to automat ically send the group data at a periodic rate as set by the Auto Send Leq function If the first variable of the group is programmed to be 146 the AUTO SEND HISTORY LEQ with a G1 146 command then the entire group will be sent out automatically when the Auto Send functions sends it s Leq This function is enabled with setting 4151 AUTO SEND HISTORY No Yes or the 151 1 command Querying and Setting Parameters
109. ms and operational mode can be altered Data can also be dumped to or queried by the controlling computer The Model 720 may be connected to the computer directly or through a modem that is initialized to be operate to be operated transparently Auto answer no echo and no responce 00150 1 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 720 and the various interface commands with their syntax These commands are a subset of the Larsone Davis Model 870 commands In this chapter we will cover the following items e Model INTO02 Interface 2 Daisy Chain Addressing sss 2 SCommniands u eda nodi dae Ee FO date 3 Group Read Programming see 11 e Querying and Setting Parameters sss 12 e Parameter 16 e History Records 22 e History Data Variables sss Print Commands Error Messages and Warnings 6 7 05 B 1 Model INTOO2 Interface Cable 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 Serial Port communication is made through the 5 pin connector at the base of the Model 720 Interface signals usually need
110. nd keys Step 1 Press SHIFT and and examine these values for the current reading Step 2 For the second screen press the gt key 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 similar to the following will appear 6 7 05 Performing a Measurement Reading the Data 5 7 veg The average RMS level is 68 2 dB The average RMS level the L slow average for the 12 minute and ing BE 14 9 second measurement period eq S displayed by press Dose DOSE the noise exposure may be calculated with three different sets of parameters Current LDL Logic Data Log 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 different dose readings Parameter 51 Full Dose Period or To protect the measurement the OVERALL Dose set Criterion Time applies to Current tings parameters 48 50 may not be modified once the Overall and LDL measurement has started without a reset However OVERALL CRITERION may be changed at any time If you wish to look at dose with different exchange and threshold values LDL may be used by modifying the LDL settings parameters 52 54
111. nd held Sound Level Meter with removable nose cone Powered internally by 9 volt cell or by an external battery or AC DC adapter e WS002 3 8 inch windscreen AC DC mini phone connector with pinout shown on page 4 7 A 5 pin cable connector with the pinout shown in fig ure Figure 1 2 note that it may be used to access exter nal power Using cable CBLO38 or INT002 and related software the 5 pin connector Figure 0 2 External 5 pin Serial Communications is used both for external power and Connector Pinout for the remote interface 1 8 Model 720 User Manual 6 7 05 Block Diagram 6 7 05 Pin 2 TXD Transmitted Data from 720 Pin 3 RXD Received Data to 720 Pin 4 Ext Batt External Battery to 720 Pin 5 DTR Data Terminal Ready from 720 Pin 1 GND Digital Signal Ground All the standard functions of a precision sound level meter are provided instantaneous level Leg SEL Lmax Lmin Dose projected dose etc In addition many valuable parameters can be stored time history interval data such as L s and Leg etc Level calibration is performed in a few key strokes and every change or check is entered in a calibration log The Model 720 s large data memory frees the user from the concern of data loss caused by memory limi tations Furthermore measurements can be printed or transmitted at up to 19 2 K baud via RS 232 for archiving Despite its numerous functions the Model 720 is easy to use A
112. ng with OVERLOAD Setting and Viewing Advanced functions 6 7 05 The Model 720 has a variety of advanced functions that allow for gathering and storing great amounts of data with any given measurement In this section we will learn how to access the parameters choose the proper settings and view some of the data collected History Functions 7 1 Time History Yes With this item set to Yes the time history function is enabled Despite Model 720 s large memory ensure anticipated requirements do not exceed available memory Normally all data is taken with 0 1 dB resolution 2 bytes level To save memory this option allows storage of history in 1 0 dB resolution This option allows saving the weighted peak Peak unweighted Peak UWPK or Max RMS level Lmax with each RMS history sam ple 7 2 Time History record includes the RMS integrated level and if selected Peak Unweighted Peak or Lmax Parameters 80 87 allow you to select the period for the history and what data are to be saved Step 1 Turn the Model 720 on and access Time His tory parameters Press G amp S The follow ing screen item 80 Time history Enable appears Step 2 To enter Yes press gt to Yes and Enter Step 3 Pressthe v toitem 81 History Resolution 1 0 dB 0 1 dB Step 4 To change this setting press gt Enter Step 5 To access item 82 Hist Save Peak press 8 No Peak UWPK Lmax Step 6
113. nn 2 Percent 0 to 99 57 Lnn3 Percent 0 to 99 58 Lnn 4 Percent 0 to 99 Exceedance Levels 61 65 V These parameters define noise threshold levels to be used when counting the number of exceedances dur ing a measurement 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 Weighted peak exceedance level 64 Uwpk Excd Level 0 255 dB Unweighted peak exceedance level 6 7 05 Parameters 8 13 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 a new exceedance can occur Normally set this level to 2 or 3 dB This prevents multiple exceedances for a single event if the level flickers around the threshold Exceedance History 66 68 162 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 exceed ance conditions above are met 67 Excd Exchange 3dB 4dB 5dB 6dB Used to calculate exceedance inte grated level Normally this is set to 3
114. nnotated 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 The block diagram below shows how the Model 720 sound level meter merges state of the art analog cir cuitry a powerful microcomputer controller and a large amount of usable data memory Introduction 1 9 The signal from the microphone preamplifier is input directly to the linear peak detector and through the selected A or C weighting filter to the root mean square 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 720 s dedicated digital proces sor 712 720 Block Diagram RMS E Slow Fast Impl Microphone 5 pin Connector Indicates parameter number Figure 0 3 Block Diagram With system programming residing in PROMs pro grammable read only memory upgrade or future changes in regulations can easily be accommodated Measurement modes are selected and shown in infor mative 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
115. not cover any products manufactured by others Such products are subject to the warranty if any of their respective manufacturers and to be repaired only by a respective authorized service person for such products LD shall have no obligation to undertake repairs of products manufactured by others June 7 2005 Model 720 User Manual D 1 NO SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES LD S SOLE OBLIGATIONS UNDER THIS LIMITED WARRANTY ARE SET FORTH ABOVE IN PARAGRAPHS B AND D IN NO EVENT SHALL LD ITS CONTRACTORS OR SUPPLIERS BE LIABLE TO THE BUYER FOR ANY LOST PROFITS DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES WHETHER BASED ON CONTRACT IN TORT OR ANY OTHER LEGAL THEORY SUCH DAMAGES FOR WHICH LD SHALL NOT BE RESPONSIBLE INCLUDE BUT ARE NOT LIMITED TO LOST TIME AND CONVENIENCE LOSS OF USE OF THE PRODUCT THE COST OF A PRODUCT RENTAL COSTS OF GASOLINE TELEPHONE TRAVEL OR LODGING THE LOSS OF PERSONAL OR COMMERCIAL PROPERTY AND THE LOSS OF REVENUE Some states do not permit the limitation or disclaimer of incidental or consequential damages Therefore the above disclaimer of incidental or consequential damages may not apply to certain purchasers NO LIABILITY IN EXCESS OF PURCHASE PRICE IN NO EVENT SHALL LD S OBLIGATIONS UNDER THIS LIMITED WARRANTY EXCEED THE PURCHASE PRICE OF THE PRODUCT PLUS ANY SHIPPING CHARGES THAT LD MAY BE OBLIGATED TO PAY PURSUANT TO PARAGRAPH C ABOVE G NO EXTENSION
116. ns of software utilize the protocol This parameter is set to the noise floor of the instru ment 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 B 23 place the Model 720 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 sensitivity 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 10dB NOTE The mode is always turned off with a CAL Change Q 210 Q CNTRLREG AUX CONTROL REG BIT Register sum the values for each bit to be set Bit Description Sum bit value Save Interval Ln Tabe Binary 1 Enable Auto Cal Check a midnight 2 Use LD Model 2400 Modem Controls 4 Take Double Cal Checks for 2202 only 8 Save Daily Ln Table Binary 16 Automatically RUN on Power On 32 Automatically Restart on Op Code Error 64 Internal flag DO NOT SET 128 211 EXCD RECORD NUMBER Q 212 Q IVREC INTV RECORD NUMBER Q 213 Q HSTREC HIST RECORD NUMBER Q214 Q LOGREC RUN LOG RECORD NUMBER Q 216 Q CALREC CALIBRATION RECORD NUMBER Q 217 Q TBLLVL LOCATE HISTOGRAM TABLE LEV
117. nter Parameters 8 3 Error Messages Parameters whose value is selected from a few possi ble choices are displayed with the current setting inside square brackets To make a selection Step 1 Press and then the M and 0 keys Step 2 Confirm change with Enter Step 3 Cancel change by pressing before Enter Entry errors will be noted by a warning message For example Verify the correct entry format Learning to Store and Retrieve Setup Memory 8 4 The current setup parameters can be stored internally in two ways for later recall In two RAM random access memory registers In one EEPROM register electronically erasable programmable read only memory Model 720 User Manual 6 7 05 Storing a Setup Remember to reset memory press U Se The EEPROM register is the default In this instance the title of the measurement 15 TECH WRITER 6 7 05 Setups stored in RAM occupy the same memory as the data 64 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 register are secure even if the batteries are disconnected for long periods of time since the EEPROM does not require bias voltage to maintain its state A minimum of 5 000 STORE opera tions are possible with the EEPROM The Model 820 must be stopped and memory reset to store to the EEPROM St
118. odel 720 Screen 2 8 Turning On the Model 720 ce eee i 2 8 Checking the Battery Voltage 2 9 Turning Off the Model 720 esce e eei te meds 2 10 Calibration 3 1 Calibrating the Model 720 ote RE RON TERES 3 2 Quick Start 4 1 Setting Parameters Using Function Keys sse 4 1 Setting Parameters Using Numbers and Other 4 2 Setting Time Date and Day 2 4 6 AC DCAOUutpUut i eite teet t x tette t e a e ea haste A 4 7 Performing a Measurement Reading the Data 5 1 Taking a Measurements ic a aea e dim hg eda Edd ele 5 1 SEM S ere e eere ERR RR e tod 5 2 Tmax TN 5 5 5 6 Chapter 6 Chapter 7 Chapter 8 Dos 5 8 BATTERY terre dei erret t rdiet te raten 5 12 MEMORY tertii defe i n ERR ainda ae 5 12 Timed Measurement 6 1 Using the Timer for Unattended Readings sssssssseeeee 6 1 Using the Time Key nene 6 4 Setting the Password Lock to Protect Settings 6 5 History Functions 7 1 Setting and Viewing Advanced functions sse 7 1 Time ee CS 7 2 Time History e eon eie 7 4 jl 7 4 Interval t tst itid oin tv ei e p ine eio 7 5 EXCeed ance zu ee on E WEN RETE N 7 8 S
119. ound of a weaker but close source can be louder than that of a more distant but stronger source Therefore measure ments 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 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 measured It is essentially the sound that interferes with a Model 720 User Manual 6 7 05 Noise Dose D Noise Exposure OSHA Level Losha Preamplifier Projected Noise Dose 6 7 05 measurement 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 spec trum White It is a random sound that contains equal energy at each frequency 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 expo s
120. pon 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 Overload These letters in succession occur alternately with the stick figure with 8 second intervals when an over load has occurred Overview to Model 720 2 7 Functionality flashing Indicates that the function keys Limin Dose etc are used for differ ent purpose in the current function Indicates that numeric key input mode is active U key active secondary function in blue lettering SrS If the Model 720 is still stabilizing upon warm up and the R S Run button is pushed will flash alternately with 5 Understanding the Model 720 Screen The operating screen for the Model 720 has several fields which vary according to the keys pressed on the keypad The most pertinent information is generally at the top and center 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 720 on and examine a variety of possible screens Turning On the Model 720 Three successive displays will appear Step 1 Press to power the Model 720 and initiate a while the meter stabilizes for 10 45 self test seconds The first display has copy right information and appears only 1 to 2 seconds 2 8 Model 720 User Manual 6 7 05 The second display
121. possible both units should be at the same temperature and stationary so that hand vibrations are not transmitted to the SLM Step 5 Press Cancel to exit calibration setup Then activate the calibrator by pressing the button on its side Model 720 User Manual 6 7 05 Pressing the will check calibra tion pressing the v will change it In this screen an error message may initially prompt for a reset The dif ference between the current and the last calibration is 0 0 db If the level is not stable enough for proper cali bration the Model 720 will exit the calibration mode without changing its calibration level The c indi cates the instrument is calibrating The Model 720 will wait until the reading is stable indicator is SsSsSs then adjust the offset for the proper reading CcCcCc An improper calibration offset for instance something greater than 34 0 dB may indicate that the cali bration tone was shut off before cali bration was completed You may repeat the previous steps or perform a Cal check The display will ask if you want to Reset ALL Data You do 6 7 05 Step 6 Press the and on the Model 720 This display indicates the current sensitivity off set and will be blinking between two set tings Step 7 Pressing key will initiate a calibra tion change Do that now Step 8 To Reset the Model 720 for re calibration press
122. pressing the or RUN STOP key In this chapter we will e Take a measurement Examine and briefly explain the function keys asso ciated with the measurement i e ive mE and W Stopping the measurement Taking a Measurement This section will address measurements and the infor mation available during and after the measurement has been taken The most basic function of the Model 720 is to measure sound pressure Follow these steps to examine the SLM function key 6 7 05 Performing a Measurement Reading the Data 5 1 SLM This instrument can store a great variety of measurements in memory depending on the current parameter setup Nevertheless current mea surements are always easily avail able from the keypad The display now reads a C weighted slow average reading of 84 5 dBC 20 uPa The level is also shown on semi analog bar graph Parame ters 39 43 affect these values and parameters 45 47 effect the Current SLM The Lmin and Lmax for the current reading at the current time are dis played in the first screen Notice that the current sound pressure level con tinues to read in the upper left cor ner and fluctuates Note that even in the stop mode the Model 720 contin ues to monitor SPL while in this window 5 2 Step 1 Turn the Model 720 on and wait for the unit to become stable Press 27 The stick figure in the upper right corner will appear to be running St
123. ps from software this truly makes the Model 720 a myriad of instruments in one In this chapter we will review the following Parameter access keys Learn to store and retrieve complete setups from the various memory registers e List all parameters with a short explanation 6 7 05 Parameters 8 1 Parameter Key Access Review Entering and Exiting the Setup Menu Master Reset If for some reason it appears that a master reset is required similar to rebooting a PC it may be accomplished with the unit off by holding down the X C and 1 key and then pushing the key Warning This is not like in that this procedure will destroy all data and setups and return the 720 to the factory default configuration You will have to re enter all your setups Locating Parameters All items in the list of parameters can be accessed by using the a and v 8 2 Some setup items may be changed while the Model 720 is running but parameters influencing data integ rity require a memory Reset ALL Step 1 Enter the setup by pressing The fol lowing will appear Step 2 exit back to the main screen press Cancel Step 3 Return to the setup menu Press When the setup menu the arrow keys allow move ment from one parameter to another One may also use a function key or directly index to the appropriate parameters Step 1 From the Setup menu press d to move down the list of parameters one
124. r press SHIFT t Remember press to change or correct the field and press Enter Step 2 To access parameters using numeric values press Step 3 To access the Current Time press 0 and then 6 The number 6 is assigned to the Current Time parameter Step4 Press to prepare the screen for changes in the Current Time Notice the flashing f changes to n Step 5 Using numeric keys make changes and press Enter or if the time is correct just press Enter Step 6 To exit the setup mode press Setting Parameters Using Numbers and Other Characters 4 2 The Model 720 has the ability to show 3 lines for your Company 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 punctu ation characters There are three levels of func tions when in the Alpha Parameter Modify Mode The charts below Figures 4 1 to 4 4 show the charac ters that are available They are listed according to the number of times you consecutively press the SHIFT key The shift indicator in the lower right corner of the Model 720 User Manual 6 7 05 This panel is available without pressing the shift key or the equiva lent of 0 presses This panel is accessed by pressing the shift key one time The S will appear in the lower rig
125. r minimal error use Model 720 User Manual 6 7 05 AC Output DC Output Reference Frequency Stabilization Time 6 7 05 instruments with 100 k34 input impedance when making AC or DC output readings Output Impedance 600 34 e 0 dB or 20 dB User Selectable Measurement Range 88 0 dB Output Impedance 600 34 Scale 20 mV dB Measurement Range 105 0 dB Voltage Range 0 to 3 volts e Temperature Coefficient 936 nV C The reference frequency is 1000 Hz The Model 720 will not proceed to a running condition until it is allowed to stabilize At power on the stabili zation time is approximately 10 seconds A shorter sta bilization time is also invoked when certain settings Weighting Detector etc are changed Microphone Electrical Impedance Functions Measured Data Storage Data Communications 8 The LarsoneDavis ADP018 should be substituted for the 3 8 microphone when performing electrical tests on the Model 720 Leg L eq max Lmin TWA SEL min Dose Projected Dose Ln 1 99 Sound Exposure in pascal squared hours SE in Pa H Time History Histograms Measurement Time Date Duration Taktmaximal 3 and 5 Exceedance Events 64k byte Memory Typically 3 month memory retention with fresh bat tery Memory protected during battery change 2 minutes minimum Serial interface for computer printer and modem communications Data Rate 19
126. r workday Step 6 To access Full Dose Hours press the v key Parameters 52 54 are a second set used to calculate overall dose from the overall data Data already in memory is recalculated with new parameters using LDL log Data Logic Step 7 Tolookat DOSE press 8 Step 8 To look at Projected Dose press gt to the PROJ b screen Step 9 If you wish to alter the LDL Exchange Threshold or Criterion settings press enter the desired values and press Enter Step 10 To look at LDL press SHIFD and 28 Dose readings are usually read and have more mean ing after the measurement is completed Return to the recent measurement and examine the values recorded there Model 720 User Manual 6 7 05 Step 1 Press the key where two screens are available Press the gt key to access the second screen 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 LDL readings are displayed on four screens View these screens using the following steps Notice in the reading the LDL Step1 Press the and keys Threshold is set at 80 parameter 49 The Overall Exchange Rate is set at 3 dB parameter 48 The overall cri terion has been set at 90 parameter 50 Any of these 3 parameters can be modified and a new dose pro jected dose and SEL will be computed eq
127. rackets in the syntax indicate optional characters and operands Syntax Response L og var_no log_var Example L1 Run Stop number L 1 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 101 Run Log Variables 11 14 all variable values Calibration History Variables Brackets in the syntax indicate optional characters Syntax Response C alibration var_no cal var Example C1 114 0 checked level Time History Variables Brackets in the syntax indicate optional characters and operands Syntax Response H istory var_no time_var 6 7 05 B 29 2 123 4 Peak level in current record H 1 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 in the syntax indicate optional characters and operands Table Number 1 RMS 2 Peak 3 Unweighted Peak If the table number is omitted then the last previously used table is selected If no table has been used then RMS is used by default Syntax Response T able var no table table var Example T
128. reased resolution I O is possi ble by using the M9 1 command All sound levels are then sent with an addi tional fractional character nnn nn giving 1 100th dB resolution The Model 720 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 9 0 Restores 1 10th dB resolution M 10 Lock 720 leave 720 s power on M 11 Lock 720 and Power Off To unlock the unit and send the lock combination to the unlock param eter with the S230 cccccccc command where is the correct combination entered before locking M 1000 Non destructive memory test walking bit M 1001 Destructive memory test pattern test M 2222 Store current settings and calibration to EEPROM 6 7 05 B 5 Read Variables Syntax Variable Description Response R1 _DEVTYPE Device manf and model String R2 _DT TM 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 5 character response e The first is an s when stabilizing or a space when ready The second is the current mode S for Stopped R for Running P Paused C for Calibrat ing V for View mode O for stopped with over all dat
129. rrent Date is the next field Press the incorrect press m to access the field v to the next display enter the correct date using the cor responding number keys and press Enter If the day is incorrect press Step4 The Day of the Week is in the next field Press and r or 1 to the correct day Press v toaccess that field Enter Step 5 To exit the setup mode press E 4 6 Model 720 User Manual 6 7 05 AC DC Output DC Output ring AC Output tip 0 Ground sleeve 6 7 05 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 the input signal to the Model 720 see Appendix A for more details CBLO42 AC Output black DC Output red Figure 0 5 AC DC Output Connector Quick Start 4 7 4 8 Model 720 User Manual 6 7 05 Performing a Measurement Reading the Data With the basic parameters set and the instrument cali brated as discussed in Chapters 3 and 4 you are ready to take a measurement and examine the read ings from the data collected Taking an actual measurement with the Model 720 only requires
130. rresponds to 1 8th dB resolution for RMS and 1dB resolution for the peak tables Q 92 RMS HISTOGRAM TABLE x Q 93 RMS HISTOGRAM TABLE LOW VALUE n Q94 RMS HISTOGRAM TABLE HI VALUE n Q95 RMS HISTOGRAM TABLE RESOLUTION x Q 96 PEAK HISTOGRAM TABLE x Q97 PEAK HISTOGRAM TABLE LOW VALUE n Q 98 PEAK HISTOGRAM TABLE HI VALUE n Q99 PEAK HISTOGRAM TABLE RESOL x Q 100 UWPK HISTOGRAM TABLE x Q 101 UWPK HISTOGRAM TABLE LOW VALUE 102 UWPK HISTOGRAM TABLE HI VALUE n Q 103 UWPK HISTOGRAM TABLE RESOL x Tailored Report Q 104 EXCD REPORT x Q 105 EXCD REPORT LOW RECORD n Q 106 EXCD REPORT HIGH RECORD n Q 107 INTV REPORT x Q 108 INTV REPORT LOW RECORD n Q 109 INTV REPORT HIGH RECORD n 6 7 05 21 Q 110 HIST REPORT Q 111 HIST REPORT LOW RECORD Q 112 HIST REPORT HIGH RECORD Miscellaneous Q 159 Q PWRMD POWER MODE Normal Ext CO Special Functions Advanced use only Remaining commands are not available on SETUP menu Q 162 Q EXTrig EXCD Passby Trigger Mode x Q 163 Q ExTime EXCD Occurrence Time x Q174 Q RTFRMT UNFORMATTED REPORTS x Q175 Q RPTBEG Begin Printing x Q176 Q PTYPE PRINTER TYPE x Q177 DATA REPORT x Q 178 R S AND CAL LOG x Q179 SETUP REPORT x Q 180 RMS HISTOGRAM TABLE x Q 181 Q RMS
131. ry 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 microphone used Some typical val ues for 2 different LarsoneDavis microphones are listed in the table below Max Level for A Weight C Weight Overload Pulses of Noise Floor Noise Floor Level cite Crest Factor dBSPL dBSPL dBSPL 10 dBSPL 30 5 30 0 35 5 142 0 145 0 124 0 Other Detectors Reference Level 6 7 05 The data in the above table was obtained by electri cally testing a number of instruments For all electrical tests the microphone was replaced with an equivalent electrical impedance LarsoneDavis ADP018 micro phone adapter Weighted Peak Detector 85 0 dB Unweighted Peak Detector 38 0 dB AC Output 85 0 dB DC Output 105 0 dB The reference level is 114 0 dB SPL Frequency Weightings The available frequency weightings for the Models 720 are described in the table below Detector A Weight C Weight Flat RMS y y Weighted Peak y Unweighted Peak AC Output 2 lt 2 e DC Output NOTES 1 The RMS frequency weighting is selected via param eter 40 Frequency Weighting The Weighted Peak Detector and DC Output frequency weighting always matches the RMS Detector frequency weighting 2 The Unweighted Peak Detector frequency weighting is sel
132. s A 10 Power Save siente einen 8 9 Preamplifier eee tes C 13 Pr Escalas 8 17 commands seen B 31 R RAM registers 8 5 Reference Direction specifications 2 Reference 8 11 specifications sss 4 Register RAM a a 8 5 Register 8 5 RESET ALL 2 gre nies 8 2 R5 232 stain etes mie binds 1 6 data communications A 8 RS 232 Address ees 8 7 RS 232 interface sse B 1 Run Log Variables 29 5 serial number eee 1 11 Setup Parameters no eei 8 6 SIOTIn gia cue cune d ee e 8 5 Setup Memory sse 8 4 SLM Sound Level Meter 8 11 Sound average level 1 C 1 day night average level C 3 energy average Leq C 17 EXPOSTO esee diede eene C 14 exposure level sss C 14 fixed average C 16 i nit nete ine C 14 PUSE C 17 instantaneous esee C 16 intensity l 17 moving average C 15 pressure eie eei C 15 sound pressure level SPL Lp C 16 unweighted peak C 17
133. s If yes automatically stops instru ment at the end of each interval for precise timing of series of manual measurements Use R S key to restart 6 7 05 Parameters 8 15 Time History 80 87 H This third type of history is the most conventional The rms integrated level and if selected a maximum read ing are stored in memory at the end of each time his tory period 80 Prompt HIST Enable Entry No Yes Comment Time history report will be stored if Yes is entered Despite the Model 720 s large memory ensure anticipated 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 storage of history with 1 dB resolution to conserve mem ory 1byte level 82 Hist Save Peak No Peak UWPk Lmax This option allows saving the his tory 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 below sets rate at which history samples are stored Ex 1 x 60 0s for minute by minute history 16 x 1 32s for 0 5 second history 85 Hist 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
134. s Hist Period Units to 1 0s Numeric Parameters Syntax Response S et item number parameter value lt cr gt lt lf gt Character String Parameters Example S62 120 sets RMS Excd Level 2 to 120 To include leading spaces in a character string parame ter precede the character string with a leading sin gle quote or grave accent ASCII 9610 or 6016 Syntax Response S et item number character string lt cr gt lt lf gt ABC Acoustics Example S2 sets Name to ABC Acoustics Template Parameters Date The month day and year are entered in that order and are separated by The display shows day month abbreviated and year in that order Syntax Response S et item number mm dd yy lt cr gt lt lf gt 22 05 23 89 sets Timer Run Date to 23May1989 Time 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 lt cr gt lt lf gt B 16 Model 720 User Manual 6 7 05 Example S24 14 25 33 sets Timer Run Time 1 to 14 25 33 6 7 05 Parameter List Q 1 Q RESALL
135. s parameter is the exchange rate used for each interval Set this to 3 dB for community noise and 5 dB for OSHA studies This sets the TWA threshold for the interoal time history For hearing conservation purposes 80 dB is rec ommended For most community 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 Model 720 allows synchronizing the interval report with the Daily History Report If Yes is entered the Interval Report will be started or restarted if already running 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 synchroniz ing the hourly levels and the interval reports is that all the statistics Limay L etc are available for the hourly noise levels that make up the daily report Yes This option allows the four Lys for the interval report to be stored 7 6 Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Model 720 User Manual To access the Interval History parameters press 9 You may also use numeric values i e 72 Enter The choices are Yes No Press the to access the next parameter 73 Into Exchange Rate for these choices 3dB 4 5dB 6dB Press the toitem 74 Into Threshold You may find 80 dB preset but you may enter another value 0 255
136. s the following data windows PSBY a Time and Date of maximum PassBy PSBY b Duration of maximum PassBy PSBY c Leg and SEL of maximum PassBy PSBY d Leq and Max RMS level Step 3 To return to the Exceedance PassBy data screens press GHIFT 4 It should be noted that during any measurement an OVERLOAD may occur Such an occurrence happens when input exceeds all reasonable parameters set by the Model 720 such as dropping or jarring the instru ment Should an OVERLOAD occur during a mea surement the data accumulated during the occurrence will not be accurate The Model 720 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 History Functions 7 13 retaken The Interval Report on the printout will indi cate which interval had the OVERLOAD 7 14 Model 720 User Manual 6 7 05 CHAPTER Parameters As we have seen in previous chapters the Model 720 owes its versatility in great part to a flexible setup More than 90 parameters and options can be selected to tailor the Model 720 to any measurement Four pre programmed setups for standard applications are in memory One may use these as blueprints for modifi cations Itis also possible to store up to 11 other setups in memory for later recall Along with downloadable setu
137. se 1 3 Octave 1 Octave A B C 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 6 0 0 1600 1 0 0 0 1 2000 2000 1 2 0 1 0 2 2500 1 3 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 logarith mic measure of the quantity and not the quantity itself The word decibel is often added after the number to express the same thing When frequency weighting is used the annota tion is often expressed as dB A or dB B The time period of measurement It applies to hearing dam age 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 associ ated with sound into an electrical voltage that duplicates the changes It can be composed of one of the following types C 10 Capacitor Condenser A microphone that uses the motion of a thin diaphragm caused by the sound to change the capaci t
138. ss M and scroll to each The will also work Note the scroll is a loop Step 10 Pressthe v or a keys to view the next or previous Interval respectively History Functions 7 7 Exceedance 7 8 Exceedance is defined as an acoustic event character ized by the sound level going above or exceeding a predetermined level An exceedance event requires the following to occur e 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 dura tion parameter 68 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 one of the four levels were exceeded will be given in the data report To find the Exceedance parameters items 61 65 turn the Model 720 on and press the Notice the available settings 0 to 255 dB for items 61 64 61 RMS Excd Lvl 1 First RMS detector exceed ance level e 62 RMS Excd Lvl 2 Set above Level 1 63 Peak Excd Level Weighted peak exceedance level 64 Uwpk Excd Level Unweighted peak exceed ance level Model 720 User Manual 6 7 05 After exceedance level must drop this amount below the exceedance threshold before a new exceedance is logged Th
139. ss the v to item 86 Hist Base Mode Off RMS Peak Step 12 To change the field press 0 Enter Step 13 Press the v to item 87 Histogram Resolu tion for these options 1 8 1 2 1 0 2 0 5 0 10 Step 14 Select the value you want Press Oo to the proper setting and then press Enter History Functions 7 3 Time History Data The Time History is used to view the data that was acquired with the set tings discussed in the previous sec tion In this example you will view the Leg and Peak data that was gath ered during the history period This display contains History infor mation about the measurement It was started by a key stroke Press the d key to view other read ings Log 7 4 In Chapter 5 we learned how to take a measurement To examine the History of that measurement take the following steps Step 1 access Time History press and a screen similar to the following will appear Step 2 Pressthe Y key to see the beginning of dozens of readings The Log key is a Run Stop log It indicates how many times the measurement was started and stopped and at what time Once the measurement is in progress information can be examined as follows Model 720 User Manual 6 7 05 This screen gives you information about the most current readings This measurement was started by a key stroke The Log screen shows the cause and action taking place In this
140. ter it may also be used as an envi ronmental 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 Introduction 1 1 About This Manual This manual has 10 chapters and 3 appendices cover ing the following topics Chapter 1 Introduction Overview of this user man ual and the Model 720 s functions and measure ment capabilities Chapter 2 Overview to Model 720 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 char acters 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 unattended readings setting additional parame ters and using the password lock Chapter 7 History Functions Setting parameters for exceedance levels and history settings interval and time history settings and daily history Chapter 8 Parameters A complete listing of all parameter items and an explanation of their basic functions Chapter 9 Memory Usage Sizing parameter needs to insure adequate memory for any given measure ment Chapter
141. tery removed a capacitor will retain memory for several minutes during battery change The Model 720 will instantly turn off should the voltage drop to less then about 4 4 V An error mes sage will be displayed at next power up Warning Power Failure Once the battery is installed the Model 720 is ready for use Environmental Considerations 1 16 The Model 720 sound level meter can be both used and stored in a wide range of temperature free of moisture and non condensing humidity conditions Some pre cautions should be taken For example allow the Model 720 ample time to adjust to abrupt temperature changes Condensation may form inside a cold Model 720 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 safeguard is to keep the instrument inside a sealed foam insulated case or bag with desiccant silica gel available at photographic equipment stores or from Larsone Davis Model 720 User Manual 6 7 05 Overview to Model 720 Once your Model 720 is unpacked and connected to a battery or external power supply you can turn it on and take simple measurements In this chapter we dis cuss the following Understanding the Model 720 Keypad Understanding the Model 720 Screen Getting
142. then the options function will be invoked after selecting that key otherwise the particular report will be printed immediately STR A permanent storage register for parameters and calibration data in EEPROM type memory that is not lost when all power is lost There are 2 RAM registers to store data R SETUP Enables the setting of desired 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 R S This key starts and stops measure ments RESET Restarts a measurement by eras ing the values just measured This func tion can be used whether a measurement is in the run or stop mode ENTER used to enter new parameters selected by the user U SHIFT Allows access to the blue letter functions on the keypad 6 7 05 Overview to Model 720 2 3 Functions EXCD The Exceedance History is 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 instru ment data and configuration The level of security is configured in Setup INTV The Interval History provides a history of a number of measurements values for a moderate size time interval 1 minute to larger than 99 hours in one minute or greater steps It is pro gramm
143. tiplied by a exponen tial 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 stan dardized 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 pres sures in all time intervals are equally weighted Sound Pressure Level SPL 1 The logarithmic form of sound pressure It is also expressed C 16 by attachment of the word decibel to the number The loga rithm is taken of the ratio of the actual sound pressure to a reference sound pressure which is 20 MicroPascals 1 Pa There are various descriptors attached to this level depend Model 720 User Manual 6 7 05 6 7 05 20 10 5 10 ing on how the actual sound pressure is 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
144. to Know Screen Symbols Turning on the Model 720 Checking the Battery Voltage Turning off the Model 720 6 7 05 Overview to Model 720 2 1 Understanding the Model 720 Keypad The keypad for the Model 720 has 20 keys as seen in the following figure Figure 2 1 5 LARSON DAVIS MODEL 720 Modify gt 7 8 9 TIME TIMER LDL Leo SEL TWA DOSE 4 5 6 CAL Luin UWPK BATT SLM LN 1 2 3 LOCK MEM LOG SHIFT exco Cancel Enter 0 OFF STR RCL RESE ON PRINT SETUP R S TYPE 2 INTEGRATING SOUND LEVEL METER Figure 0 1 Model 720 Keypad 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 buttons directly Blue Blue 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 2 2 Model 720 User Manual 6 7 05 Functions O ON Turns on the Model 720 CANCEL When the Model 720 is on this button serves to return to a previous menu or Cancel the present function OFF SHIFT OFF turns off the Model 720 after it has been stopped 5 Print Access to a list of reports scrolled through the display a key name is indi cated for each one If there is fol lowing the key name
145. to be converted for proper com munication with desktop computers The Model INT002 Cable Level Converter is required for this purpose Its electronic circuits provide the correct RS 232 signal levels and polarities When used with the AC DC adapter the INTOO2 also powers the units externally minimizing battery depletion during Serial Port transfers Step 1 With the instrument turned off insert the cable connector in the 5 pin port Step 2 Connect the cable to the of the computer using the supplied 9 25 pin adapter if neces sary Signal 5 Pin configurations for the INT002 follow 712 720 812 amp 820 5 pin Connector omputer DB 9 Pin 2 Red Pin3 Yellow Pin4 Blue Pin 5 White Pin 3 Red Pin 2 Yellow Pin 4 Blue Pin 6 White Pin 8 White Daisy Chain Addressing The following instruments are com patible on a common network Mod els 712 720 812 820 870 and TAC100 Future instruments may also be compatible with this network B 2 A network of instruments may be interconnected to one computer using the appropriate cabling such as the CBL040 and each may be controlled individually Each is given a unique address parameter 10 The addresses are sent as a single byte ranging in value from 129 to 255 representing address 1 to 127 respec tively address plus 128 Whenever an address byte is received only the corresponding instrument is enabled to receive commands Model 720 User Manual 6 7 05
146. two is logarith mic rms 20 L 201080 po10 0 where p is the reference sound pressure of 20 pPa 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 10 L toes P Prms 10 Sound Pressure Level can be converted to sound pressure as follows If the sound pressure is 1 Pascal then the sound pressure level is L 20108 201og 50000 20 4 699 94 04B 20 e 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 pres sure is 763 20 Z 20 10735 5 20 19755 20 0 0065 0 13 Energy Average Leq 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 C 17 Sound Power W 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 Weighted Peak The peak value of a sound with a meter that has a frequency weighting other than flat and a peak detec tor The sound power emitted by a sound source It is measured in Watts Sound Power Level PWL L The logarithmic form o
147. u bling or halving of the duration of a sound level while a con stant percentage of criterion exposure is maintained The 6 7 05 5 Far Field Free Field Frequency Hz rad sec C 6 rate and the factors are given in the table below Standard ANSI 12 19 Exchange Rate Q Exchange Rate Exposure Factor Factor q 3 01 10 1 4 13 333 75 5 16 667 60 6 02 20 50 There are two types of far fields the acoustic far field and the geometric 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 frequency See the definition of Wavelength the distance will vary with frequency To be in the far field for all frequencies measured the lowest fre quency should be chosen for determining the distance For example if the lowest frequency is 20 Hz the wavelength 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 in the far f
148. uld expose a person to the same Noise Dose as the actual unsteady sound over the same period If the Exchange Rate is 3 dB then the TWA is equal to the Leg 1 L t K T where and 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 mea surements Fast The time constant is 1 8 second 125 ms This is a less commonly used weighting but will detect changes in sound level more rapidly Impulse The time constant is 35ms for the rise and 1 5 sec onds 1500 ms for the decay The reason for the double con stant 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 descriptor of oscilla tions The distance between peaks of a propagating wave with a well defined frequency It is related to the frequency through the following equation Wavenumber where is the sound speed 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 wave length or the time delay in sound propagation It is related to wavelength throug
149. ure and 100 or more represents complete exposure It is cal culated by dividing the actual time of exposure by the allowed time of exposure 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 frequency weighting and slow exponential time weighting See Projected Noise Dose _ 100T qu 1 0 D 1005 007 0 where T is the Measurement Duration and T is the Allowed Exposure Time Standard ANSI 12 19 See Sound Exposure The Average Sound Level calculated in accordance with the Occupational Safety and Health Administration Exchange Rate and Threshold Level A part of the sound level meter that matches a particular model of microphone to the meter It must be chosen in con junction with a microphone and a cable that connects them It is the Noise Dose expected if the current rate of noise expo sure continues for the full Criterion Duration period Single Event Noise Exposure Level SENEL Lax The total sound energy over a specific Sound Sound Exposure SE period It 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 It is characterized by changes in d
150. weighted C 17 yearly average level YDNL Lydn C 20 Sound Level threshold Lt 18 Sound Level Meter JB 8 11 Sound Power seen C 17 level PWL Lw eer C 17 Sound Pressure Level see Sound C 16 Sound Speed AAA C 17 Specifications frequency weightings 4 reference direction A 2 reference 1 A 4 temperature sse A 6 A A Hae Hades A 2 Spectrum frequency eret eter C 18 Standards ANS tddi os A 10 Status command sesta B 6 Store determine strorable data 9 1 Index 3 T Temperature specifications sess 6 template nie ee eto B 16 Template Parameters B 16 Threshold 4 edes 8 12 Time allowed Exposure time Ti 1 weighting iiie eet C 19 Time History i eai oe hende eas 8 15 TWA time weighted average sound level TWA LTWA TC C 18 Type specifications sss A 2 Type2 utei ierit 1 4 U Unweight d eee tette 5 3 V Variables calibration history B 29 exceedance B 26 histogram eee tte 30 histogram table 30 interval sisse eet B 27 interval history sss 27 rundlog A B 29

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