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VPF-710- User Manual

1. Command Function Response 710 730 750 Send precipitation matrix accumulated over last measurement periods M nnn nnn This is a matrix of 16 rows with up to 21 3 1 3 readings Zeros to right not displayed OP Check Option Word configuration See 1 4 1 V y y Set configuration options See para 1 4 1 OK OSAM Check automatic message setting See para 1 47 V OSAMx Set automatic message setting para 1 4 7 OK y y OSCM Check message type setting See para 1 4 8 OSCMx Set message type setting See para 1 4 8 OK y y y OSHH Check hood heater setting See para 1 4 9 OSHHx Set hood heater setting See para 1 4 9 OK OSWH Check window heater setting See para 1 4 10 V y y OSWHx Set window heater setting See para 1 4 10 OK Send program version message SI xxxx yy y y y R Send remote self test and monitoring message RST Restart instrument OK Send instrument times message See 3 1 2 SN Send instrument serial number JXXXX XX Set auxiliary measurement sample period y Range x 2 20 seconds Default 5 Set measurement interval IM Vo fv fv Range x 10 300 seconds Default 60 Send current date and time See paragraph F
2. If you need to return the sensor ener nnne vii CE Certification Safety cA teet re teen 56 1 1 1 STEP 1 Unpacking the sensor eee 2 1 2 STEP 2 Electrical Connections 2 4 1 3 STEP 3 Equipment Test sse ener 8 1 4 STEP 4 Configuration Options 10 1 5 STEP 5 Installation ee eere tere 21 1 6 STEP 6 Test and Commissioning essere 28 STANDARD OPERATING DATA nas s ens aa 31 2 1 Data Output Message 10 32 2 2 Data Output Message 730 0 0 34 2 3 Data Message Variations For ALS WSM VPF710 and VPF730 38 2 4 Data Output Message 750 39 COMMANDS AND RESPONSE G ccssccssssssccsssssccesscrsccsscsscsesssrsesesssrsesessonees 48 3 1 Sensor Commands eerte a Le deese een reale dvo apa 48 3 2 Sensor Responses ences etnies ce re Dir a i Ree er 53 MAINTENANCE 1 sesenta ses eese ses 54 4 1 General Checks 5 Ve ett tens 54 4 2 Self Test Codes tt ee TE eletti rores a 55 4 3 User Confidence Checks e
3. Sensor Set up 1 5 STEP 5 Installation Please consider the following factors when installing the sensor 1 Siting considerations 2 Height of the sensor above ground 3 Orientation of the sensor 4 Mounting the sensor 5 Electrical grounding Each of these factors is covered in more detail below 1 5 1 Siting Considerations Pollutants Care should be taken to ensure that the sensor 15 situated away from any possible sources of pollutants for example car exhausts air conditioning outlets etc Particulates entering the sensor s sample volume will cause errors in the reported visibility measurements and precipitation reports Reflected Light Care should be taken to ensure that the sensor is situated away from any causes of reflected light for example walls trees and people etc Reflected light entering the sensor s optics will cause errors in the reported visibility measurements Air flow Care should be taken to ensure that the sensor is situated away from objects that disrupt the normal flow of air to and through the sensor sampling volume for example walls trees and other equipment etc RFI Interference In addition to the above mentioned natural effects that may influence the performance of the sensor due regard should also be given to radiated electrical interference Sources of potential interference include radio antennas and radi
4. Section 2 Message Meaning hh Transmitter window contamination 00 to 99 iii Forward scatter receiver gain 80 to 120 jj Receiver window contamination 00 to 99 kkkk AC interrupts per second Temperature C mmmm Not used es If selected this will be the checksum character The checksum is off by default Table 2 2 VPF710 Expanded Data Message Two typical expanded data messages from a VPF710 are as follows vs01 000 55 xX00 100000 2 510 00 82 100 00 100 00 4040 002 5 0000 Vs01 000 56 xX00 100000 2 509 00 82 100 00 100 00 4040 003 0 0000 2 2 Data Output Message VPF730 2 2 1 VPF730 Compressed Data Message The data message format is lt Date gt lt Time gt CPaa bb ccc cc dd dddd eee e fff lt cs gt lt crlf gt Message Meaning lt Date gt Optional Date string in the form DD MM YY lt Time gt Optional Time string in the form HH MM SS CP Compressed message header aa Instrument identification number set by the user Present weather codes From WMO Table 4680 Automatic Weather Station bb 00 No significant weather observed or sensor starting 04 Haze or Smoke or Dust 30 Fog 40 Indeterminate precipitation type 34 Data Output Message VPF730 Section Standard Operating Data Messag
5. Message Meaning lt Date gt Optional Date string in the form DD MM YY lt Time gt Optional Time string in the form HH MM SS VPF750 Model number nnn Instrument identification number set by the user XXXX Averaging time period in seconds aa aa KM Meteorological Optical Range KM This is the averaged value Present weather codes From WMO Table 4680 Automatic Weather Station XX Not Ready first 5 minutes from restart 00 No significant weather observed 04 Haze or Smoke or Dust 10 Mist 20 Fog in last hour but not at time of observation 21 Precipitation in last hour but not at time of observation 22 Drizzle in last hour but not at time of observation 23 Rain in last hour but not at time of observation 24 Snow in last hour but not at time of observation 25 Freezing Drizzle or Freezing Rain in last hour but not at time of observation 30 Fog 31 Fog in patches 32 Fog become thinner in last hour 33 Fog no appreciable change in last hour 34 Fog begun or become thicker in last hour 35 Freezing Fog 40 Indeterminate Precipitation Type 51 Slight Drizzle 52 Moderate Drizzle 53 Heavy Drizzle 54 Freezing Slight Drizzle 55 Freezing Moderate Drizzle 56 Freezing Heavy Drizzle 57 Slight Drizzle and Rain 58 Moderate or Heavy Drizzle and Rain 61 Slight Rain 42 Data Output Message VPF750 Section 2 Standard Operating Data Message Meaning 62
6. Sensor Set up VPF710 Orientation The VPF710 receiver optics should be aligned with true North true South in the Southern Hemisphere as shown in Figure 1 4 VPF710 Orientation N e 068 North 0 5 p Instrument Front Figure 1 4 VPF710 Orientation VPF730 and VPF750 Orientation The VPF730 and VPF750 alignment should be such that neither the forward nor the backscatter receiver optics is aligned with the rising or setting sun For the Northern Hemisphere the best mounting orientation is shown in Figure 1 5 VPF730 and VPF750 Orientation for the Southern Hemisphere the bearings should be increased by 180 V 034 Instrument Front Figure 1 5 VPF730 and VPF750 Orientation STEP 5 Installation 23 Biral Sensor Set up Section 1 1 5 4 Mounting the Sensor Models The sensor head should be attached at the very top of the mounting pedestal with a U bolt The mast should be made from galvanised steel pipe or heavy walled aluminium tube whose outer diameter is in the range from 40 to 64 mm NOTE The maximum diameter for the VPF750 temperature and humidity radiation shield is 50mm Pipe or tubing with an outer diameter greater than 66 mm will not permit use of the U bolt provided with the instrument Pipe diameters less than 40 mm
7. Section Standard Operating Data 2 1 2 VPF710 Expanded Data Message The data message format is lt Date gt lt Time gt VSaa bbb bb ccc dddddd e eee ff ff gg g hh iii jj kKkkk 1 1 mmmm lt cs gt lt crlf gt Message Meaning lt Date gt Optional Date string in the form DD MM YY lt Time gt Optional Time string in the form HH MM SS VS Expanded visibility sensor message header aa Instrument identification number set by the user bbb bb Total EXCO in km Self Test and Monitoring see paragraph 4 2 O Other self test values OK X Other self test fault exists O Windows not contaminated X Windows contaminated cleaning recommended required F Windows contaminated fault O Sensor not reset since last R command X Sensor reset since last R command dddddd Error Status Bit 1 Transmitter Sync Signal Missing Bit 2 A D control signal error Bit 3 RAM Error Detected Bit 4 EPROM check sum error Bit 5 Non volatile memory check sum error Bit 6 Sensor reset has occurred e eee A D reference channel measured voltage 2 450 to 2 550 ff ff Forward scatter receiver background illumination 00 00 to 10 00 ggg Infra red optical power 85 to 110 2 Data Output Message VPF710 33 Biral Standard Operating Data
8. 89 Table 7 5 US Precipitation Intensity Definitions 90 Table 7 6 Sensor ene 94 Table 7 7 Instrument Characteristics eese 96 Table 7 8 Digital Communication Interface Specifications sss 97 iii General Information The sensors covered in this manual Sensor Model Capability VPF710 Visibility VPF730 Visibility Precipitation type identification This model has an extra backscatter receiver for Rain rate Snowfall rate Precipitation accumulation VPF750 Visibility Precipitation type identification This model has an extra precipitation sensor and an extra high accuracy temperature and humidity sensor for 50 weather codes from WMO Code Table 4680 including Past Weather Freezing Rain Ice Pellets iv Biral PATENT COVERAGE The Present Weather Measurement Techniques are protected by the following Patents U S Patent No 4 613 938 Canadian Patent No 1 229 240 German Patent No 3 590 723 RoHS Compliant Thank you for choosing Biral as your supplier of Present Weather Sensors A great deal of time has been invested at Biral to offer the best combination of sensor performance and value and almost three decades of experience and knowledge have been incorporated into the HSS Sensors We are confident that they will provide you wit
9. ats as fates an ars eaters mde a e a M D I VN SAVM 5 2 1 VN c v y V 1 I I I H3171I4 SSVdONVE l H311V2S I I 1 1 1 1 1 i H3AIJO3H 1 i HSILIMSNVHL ______________11____________ 11 26 1 1 I l i I eee I 1 HEALING 32unos veges L aaae L 1 aded H0123130 I IWYS Figure 6 4 VPF730 Sensor Functional Block Diagram 81 Precipitation Measurements Biral Product Overview Section 7 7 PRODUCT OVERVIEW 7 1 VPF700 Series of Present Weather Sensors 7 1 1 Available Sensor Models There are three models in the VPF700 series of present weather sensors the VPF710 the VPF730 and the VPF750 They use the same basic opto mechanical and electronic components and have an optical transmitter and forward scatter receiver The VPF730 and VPF750 also have a
10. Sensor Set up Data This is a variable length ASCII character string as defined in section 2 for each of the models in this range The master has a defined range of commands available for the HSS sensor The HSS sensor has a range of defined data messages These messages can either be sent as a response to a request for data by the master unit or sent without any request on a timed basis according to the instrument user settable configuration However it is recommended that a polled system is used in a multi sensor application as this can avoid most data contention issues through the design of a suitable system operating schedule LRC Checksum This enables error checking allowing the master to request a re send if errors are detected For RS485 a Longitudinal Redundancy Check LRC Checksum is generated on the data NOTE This checksum is different from the standard HSS Checksum The LRC is one byte containing an 8 bit binary value The LRC value is calculated by the transmitting device which appends the LRC to the message The receiving device calculates an LRC during receipt of the message and compares the calculated value to the actual value it received in the LRC field If the two values are not equal an error is implied The LRC is calculated by adding together successive 8 bit bytes of the message discarding any carries and then two s complementing the result It is performed on the ASCII message field contents ex
11. ren e i b 1200 9600 on VPF750 Data Bits ons reU 8 Stop tin aedes 1 te nete e Nets None Flow tnde 8 STEP 3 Equipment Test Biral Section 1 Sensor Set up If using Hyper Terminal the options Send line ends with line feeds and Echo typed characters locally in ASCII set up should be checked Turn the local power source ON If communications are working the sensor will respond with Biral Sensor Startup Check Data Transmission To Sensor Send the command R from the PC terminal to the sensor The sensor will respond with its Remote Self Test amp Monitoring Message For example 100 2 509 24 1 12 3 5 01 12 5 00 00 00 00 100 105 107 00 00 00 021 0 4063 Check Data Transmission From Sensor If the sensor is NOT in polled mode Wait for the sensor to transmit a Data Message approx 80 seconds from power up If the sensor is in polled mode Send the command D from the PC terminal to the sensor A Data Message will be transmitted immediately EXCO Calibration check THIS PROCEDURE CAN ONLY BE COMPLETED IF A SUITABLE VPF700 SERIES CALIBRATION KIT AND PC ARE AVAILABLE Biral Carry out the calibration check procedure in paragraph 5 1 page 61 to ensure that the EXCO value changes i e the sensor responds to changes in visibility NOTE As this calibration check is being carried out indoor
12. 5 1 d eee ind edi cd er tt eite le sehe 21 XPETS0 ASSembly zer e RR ER ER XU EE EU D Un E eee 26 RATNG desorden D ERRORES ERES DS aye KI SR EIER TRE e EISE P E Yer Ee E PERENNE TER Euren 96 M MAINS ADAPTER 3 MAINTENANCE PROCEDURES EE Deko 54 60 General CHECKS rrt re i e tete beta eiie peter adde 54 54 Mindow Cleanme De oo Dd Do D edic rete oe e py 55 Window Heaters eee eee de tie date 54 Sel Test Codes ded cene bg ee ce e b bed eo E Ee 55 UserContidence Checks edere ter eru PER re Ee SUE 58 EXCO Calibration Check gite e ete he unb 58 Receiver Background Brightness esses eene enne eene enne enne 60 Temperature Calibration Ch ck eH Dette ede eb e de 58 WmdowMotnitor SUL Ep Eee 58 MEASUREMENT PRINCIPLES 5 259 VAASASSA EMEA NEEN SANS AEKA EA AESA rea 68 EXCO Primary Calibrati n e a erp e ed eene aO n 71 Meteorological Optical 1 21 2 1 0 2 2010000000000000000000000000 0000 00 0 5 0 70 Precipitation Identificationi a be el e tet TT Precipitation Measurements nente nennen ntn enne tsentre tsenter 76 Precipitation Recognition 77 80
13. Biral OPERATION and MAINTENANCE MANUAL VPF Present Weather Sensors VPF710 VPF730 VPF750 PROPRIETARY NOTICE The information contained in this manual including all illustrations drawings schematics and parts lists is proprietary to BIRAL It is provided for the sole purpose of aiding the buyer or user in operating and maintaining the instrument This information is not to be used for the manufacture or sale of similar items without written permission COPYRIGHT NOTICE No part of this manual may be reproduced without the express permission of BIRAL 2014 Bristol Industrial and Research Associates Limited BIRAL Biral Biral P O Box 2 Portishead Bristol BS20 7JB UK Tel 44 0 1275 847787 Fax 44 0 1275 847303 Email info biral com www biral com Manual Number 102186 Revision 06C Biral CONTENTS ii GENERAL INFORMATION 10 1 BOUE 11 b tbt ale Ra ei iii 2 ea iii The sensors covered in this iv Features of the HSS Customer satisfaction and After Sales 2 vi Contacting dt tae eerie Gath coll staat vi
14. Table 7 2 Additional Measurement Capabilities of the VPF730 and VPF750 Additional Precipitation Obstruction to Vision Measurements VPF750 Function Details Drizzle and Rain Slight Moderate Heavy Non Freezing Freezing Fog Freezing Drizzle Slight Moderate Heavy Freezing Rain Slight Moderate Heavy Identification Intensity Rain Drizzle and Snow Slight Moderate Heavy Freezing Ice Pellets Slight Moderate Heavy Snow Grains Ice Crystals Hail Smoke HZ Obstruction to Vision Dust DU Mist BR Table 7 3 Additional Precipitation Obstruction to Vision VPF750 88 Present Weather Measurements Biral Section 7 gt gt gt Product Overview Past Weather Determination VPF750 Function Time Constraints Fog In last hour but not at time of observation Precipitation In last hour but not at time of observation Drizzle In last hour but not at time of observation Rain In last hour but not at time of observation Snow In last hour but not at time of observation Freezing Drizzle or Rain In last hour but not at time of observation In patches Fog Becoming thinner in tast hour No appreciable change in last hour Begun or becomming thicker in last hour Rain showers Slight Moderate Heavy Snow Showers Slight Moderate Heavy Table 7 4 Past Weather determination Types 750 In the presence of prec
15. command or any combination of these 1 e if both the window and hood heaters are ON the first character A would be 3 The normal running value for this is 100 which is widow heaters ON and no fault condition Field3 2 450 2 550 Internal reference voltage Field 4 9 00 36 00 Supply voltage for DC sensors only Field5 11 15 0 Internal operating voltage B 8 C 2 4 Field6 4 5 5 5 Internal operating voltage Field 7 11 15 0 Internal operating voltage Field 8 0 00 6 00 Forward scatter background brightness Field 9 0 00 6 00 Backscatter background brightness Not VPF710 Field 10 85 105 Transmitter power monitor Field 11 80 120 Forward receiver monitor Advanced self test only Field 12 80 120 Back receiver monitor Advanced self test only Not VPF710 Field 13 00 99 Transmitter window contamination Field 14 00 99 Forward receiver window contamination Optional Advanced self test only Field 15 00 99 Back scatter receiver window contamination Optional Advanced self test only Not VPF710 Field 16 Temperature C Field 17 3300 4200 ADC interrupts per second Table 3 2 Command R Response 51 Sensor Commands Biral Commands and Responses 5 Section 3 1 2 Command Send Instrument Times Message Response aaaa bbbb cccec dddd Measurement interval for each operational data message 10 to 300 seconds default 60 Aux
16. illustrated in the matrix are also borne out in practice 6 5 3 Signal Processing A functional block diagram of the VPF700 series of sensors is shown in Figure 6 4 VPF730 Sensor Functional Block Diagram Those components of the sensor housed in the transmitter and receivers are shown enclosed in one dashed line Those components housed in the power control system are shown enclosed in the other dashed line When a particle of precipitation passes through the sample volume light from the LED source which is housed in the transmitter section of the sensor head is scattered into the receiver section where it is sensed by the photo detector Because the LED source is modulated at a 2 kHz frequency the detector and amplifier chain generates an AC signal whose amplitude is proportionally to the size of the particle and whose duration is inversely proportional to its velocity 78 Precipitation Measurements Biral 6 Measurement Principles 6 5 4 Quantity and Intensity Typically a sampling time interval of one minute is employed in automated present weather sensors When rain is identified the quantity of water falling in the one minute sampling time interval is determined from the number and size of the raindrops passing through the sample volume The intensity is established by a comparison of the quantity of rainfall in one minute with the rate of fall intensity scale published in t
17. Light Source Function Details Type IRED Central Wavelength 0 85um Bandwidth 0 04um Lifetime gt 10 years Modulation Frequency 2000 Hz Detector Function Details Type Photovoltaic Silicon Response Silicon Filter Bandwidth 0 08um at 0 85um Power Requirements Function Details Basic Sensor 3 5 W De Icing Heaters Optional VPF710 30W 17W for 12V DC Version VPF730 45W 25W for 12V DC Version VPF750 45W No Dew Window Heaters VPF710 1 7 W VPF730 and VPF750 2 5 W VPF750 Additional Sensors Precipitation Sensor Temperature and Humidity Sensor Ambient Light Sensor 17W 0 2W 2 0W 17W with optional hood heater Sensor Specifications 95 Product Overview Section 7 Environmental Function Details Operating Temperature Range 50 C to 60 C Altitude 0 to 20 000 ft Precipitation weather Humidity 0 to 100 Protection Rating IP66 CE Certified y EMC Compliant EN61326 1997 1998 2001 RoHS and WEE Compliance Table 7 7 Instrument Characteristics 7 42 Digital Communication Interface Communication Protocols Function Details Interface Type RS232C Full Duplex Optional RS422 or RS485 Parameters Function Details Baud Rates 1200 Baud to 57K6 Baud selectable Data Bits 8 Parity None Stop Bits 1 Flow Contro
18. The type of precipitation is established by one of two independent techniques In one of the techniques the ratio of the back scatter atmospheric extinction coefficient BACK SCATTER EXCO to the forward scatter atmospheric extinction coefficient FORWARD SCATTER EXCO is determined A ratio greater than a specific value indicates snow while a ratio lower than a specific value indicates rain In the second the size and velocity distributions of the precipitation particle are used to determine the type of precipitation These two techniques are intended to complement one another However under some circumstances one of the techniques is programmed to override the other The particular circumstance under which the one is programmed to veto the other has been established by several years of empirical observations 6 5 2 Precipitation Recognition Matrix The VPF 700 series of sensors measure the amplitude and duration of the light pulse created by each precipitation particle as it falls through the sample volume From the amplitude and duration it then determines the particle size and velocity The size and velocity information is collected in a data matrix by the microcomputer and is stored for a time interval the measurement time period usually one minute adequate to provide a statistically significant and representative sample of particle sizes and velocities The size and velocity distributions of particles in the matrix are available to determine
19. Theory of Forward Scatter Meters 71 Visual Range Determination 68 METAR CODE eit etr E DP re ast ctae UITAE ET D NES 43 47 ooo e RERO OD 46 METEOROLOGICAL OPTICAL RANGE eee ite tp tore e pee I eo HE Sora eL de 64 87 MOUNTING THE SENSOR V BE730 ede apte ere tdt ne 24 VIBE FO ss os cared Cte e d ORI 25 OPTIONAL ACCESSORIES 11 3 84 Ambient Light Sensor de eate e e i tl tales 3 External High Accuracy Temperature and Humidity Sensor seen 3 Manis Adaptor ene cp eate rei edd ela e Red Ea 3 Transi EE 3 102 Index Section 7 Product Overview Weather Station Modules ensi ee 3 eerie bet ee o e a ipei des SEE INSTALLATION P PAST WEATHER VPE750 2 eR RAE be ate eed eas 89 POWER CONNEC NONS tcm 5 7 PRECIPITATION AMOUNT CALIBRATION sinian in raaa aa aia ia E e EE a a a aiai 66 PRECIPITATION IDENTIFICATION isc E Use eo RES 77 PRECIPITATION MEASUREMENTS 205 etre be prece i 8
20. e e e EE NR e p ed re DEED 4 NV PETI O PE 4 MPE eor ele wrk AE 4 MERE TSO E E E A EE 5 2 VPF700 Dimensions 103 Biral Index Section 8 SENSOR DIMENSI NS 5 5 ene en eed 99 SENSOR PEA TURES d reti e e eb tee pter bir ebat fere a Ree saa epi eee ea todas 85 SENSOR RESPONSES Date eure ote ERU S Fe lr e e PAESE ERES OF AE 53 Niaskiedigrelidie Wue EE S S 93 99 2520 bed de te 6 TEMPERATURE AND HUMIDITY SENSOR EXTERNAL HIGH 3 36 57 66 TEST AND COMMISSIONING c sscccccsessssscecesceseesecececsessesececececcessececececseseceeceesenssaeeecececsesssseeeces senssaseeeeeeeees 8 28 TIMESTAMP D 11 TRANSIT CASE c re entere 3 WROUBEESHOOTING TE epe d EINE 28 Calibration Checker crm tret bases y HER 30 Checking Data link
21. than 90 degrees by small particulates suspended in or large particles passing through its sample volume In the case of the VPF700 Series of Sensors the sample volume is defined by the intersection of the transmitted beam of light and the ray cone which defines the field of view of the forward scatter receiver as shown in Figure 6 1 Sensor Sample Volume Receiver Transmitter Figure 6 1 Sensor Sample Volume Suspended particles such as fog haze and smoke aerosols and precipitating particles such as rain snow ice pellets drizzle and mist account for essentially all of the atmospheric extinction of visible and near visible optical radiation for horizontal visual ranges up to approximately 100 kilometres Beyond that range scattering by the molecular constituents of the atmosphere begin to play a role In the visible and near visible spectral regions the dominant aerosol attenuation process is Mie scattering Aerosol absorption plays a negligible role in most natural environments thus the atmosphere scattering coefficient and extinction coefficient are synonymous Visual Range Determination Nearly all instrumental methods of determining visual range start with a quantitative measurement of the atmospheric extinction coefficient Because is measured in the vicinity of the instrument an assumption must be made that the prevailing environmental conditions are uniform over the scale of visual ranges of interest The extinction co
22. 1 2 DC Power Connections Section 1 1 2 5 Data Connections not combined power data cable see para 1 2 6 RS232 Signal Connections When operating in the RS232 interface mode the output signal cable furnished with the sensor has the following pin and conductor assignments The cable consists of 3 sets of twisted pairs The Function data refers to the SENSOR function Pin Pair Conductor Function Number Number Colour A 1 Red Tx Data B 1 White Not Used 2 Brown Rx Data D 2 White Not Used E 3 Grey Signal Ground F 3 White Sensor Chassis Ground Table 1 3 RS232 Signal Connections RS422 485 Signal Connections When operating with the RS422 or RS485 interface protocols the output signal cable furnished with the sensor has the following pin and conductor assignments The cable consists of 3 sets of twisted pairs The Function data refers to the SENSOR function Pin Pair Conductor Function Number Number Colour A 1 Red Tx Data B 1 White Tx Data 2 Brown Rx Data D 2 White Rx Data E 3 Grey Signal Ground F 3 White Sensor Chassis Ground Table 1 4 RS422 485 Signal Connections STEP 2 Electrical connections Biral Section Sensor Set up 1 2 6 Option Single Combined Power and Data Cable When configured for a single combined power
23. 85 Product Overview S Section 7 Ease of Maintenance and Calibration Routine maintenance including a check on calibrations is performed in a matter of a few minutes A re calibration if required takes only slightly longer and is easily performed by one person 7 2 1 Real Time Data Displays The output of the sensor is a serial digital message that is provided at the signal interface at a sample time interval selected by the operator a typical sample time interval is one minute The message is provided automatically or if the sensor is in the polled mode the data message is transmitted after the polling command is sent to the sensor A printer can be used to record the data message However a PC terminal offers much more flexibility 1 Each message can be time tagged with the date and time 2 Data processing can occur such as the application of Allard s Law for visibility of point light sources 3 Precipitation accumulation for selected intervals of time e g every hour every six hours every 24 hours etc can be obtained not VPF710 4 or selected parts of the data message can be archived 7 3 Present Weather Measurements 86 7 31 Present Weather Definition The term Present Weather is generally employed to define a large class of atmospheric phenomena that includes tornado activity thunderstorm activity precipitation obstructions to vision and other atmospheric phenomena such as
24. Drizzle and Rain slight 46 Data Output Message VPF750 Biral Section 2 Standard Operating Data Code METAR Number Code 58 RADZ Drizzle and Rain moderate 58 RADZ Drizzle and Rain heavy 61 RA Rain not freezing slight 62 RA Rain not freezing moderate 63 RA Rain not freezing heavy 64 FZRA Rain freezing slight 65 FZRA Rain freezing moderate 66 FZRA Rain freezing heavy 67 RASN Rain or Drizzle and Snow slight 68 RASN Rain or Drizzle and Snow moderate 68 RASN Rain or Drizzle and Snow heavy 71 SN Snow slight 72 SN Snow moderate 73 SN Snow heavy 74 PL Ice Pellets slight 75 PL Ice Pellets moderate 76 PL Ice Pellets heavy 77 SG Snow Grains 78 IC Ice Crystals 81 SHRA Rain Showers slight 82 SHRA Rain Showers moderate 83 SHRA Rain Showers heavy 85 SHSN Snow Showers slight 86 SHSN Snow Showers moderate 87 SHSN Snow Showers heavy 89 GS Small Hail 89 GR Hail Biral Table 2 9 METAR Codes Data Output Message VPF750 47 Commands and Responses Section 3 COMMANDS AND RESPONSES 3 1 Sensor Commands commands should be terminated with Carriage Return and Line Feed crlf see Paragraph 1 3 Command Function Response 710 730 750 Send accumulated precipitation message XXX XX XXXX X A Accumulat
25. Moderate Rain 63 Heavy Rain 64 Freezing Slight Rain 65 Freezing Moderate Rain 66 Freezing Heavy Rain 67 Slight Rain and Snow 68 Moderate or Heavy Rain and Snow 71 Slight Snow 72 Moderate Snow 73 Heavy Snow 74 Slight Ice Pellets 75 Moderate Ice Pellets 76 Heavy Ice Pellets 77 Snow Grains 78 Ice Crystals 81 Slight Rain Showers 82 Moderate Rain Showers 83 Heavy Rain Showers 85 Slight Snow Showers 86 Moderate Snow Showers 87 Heavy Snow Showers 89 Hail Past Weather Typel SYNOP Code i No past weather code 4 Fog or Thick Haze 5 Drizzle 6 Rain 7 Snow or Mixed rain amp snow 8 Showers Past Weather Type2 SYNOP Code No past weather code 4 Fog or Thick Haze 5 Drizzle 6 Rain 7 Snow or Mixed rain amp snow 8 Showers Obstruction to Vision Message dd Blank No obstruction HZ Haze FG Fog DU Dust FU Smoke BR Mist eeeee METAR Reporting Code See Table 2 9 METAR Codes paragraph 2 4 3 Biral Data Output Message VPF750 43 Standard Operating Data Section 2 Message Meaning fff fff Precipitation Rate mm hr gg gg Meteorological Optical Range KM This is the instantaneous value hhh hh Total Exco KM This is the averaged value Back Scatter Channel Exco KM This is averaged value Temperature Relative Humidity Precipitation Indication xmmmmm ALS signal minute average value nnn Self Test and Moni
26. Section 4 60 Step 7 Step 8 Step 9 Step 10 Send the command R Verify that the Forward Scatter Receiver Window Contamination field value in the sensor response is much greater than 10 ie 99 Remove the white card For the VPF730 and VPF750 repeat steps 1 to 9 but applying to the back scatter head and the Back Scatter Receiver Window Contamination field value in the sensor response 4 3 4 Receiver Background Brightness Measurement Checks The receiver background brightness value measures the optical signal detected by the receiver caused by the intensity of the ambient background This value is used to set the threshold values for precipitation particle detection and interpretation The following procedure will check this function this procedure is used for both the forward scatter and backscatter receivers For the VPF710 sensor only carry out the forward scatter test Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Insert a zero plug part of the VPF 700 sensor calibration kit in the receiver hoods blocking all light from the window Send the command R Verify that the value in the Forward Scatter Receiver Background Brightness field in the sensor response see paragraph 3 1 1 is less than 00 06 Remove the zero plugs from the Sensor Head receiver hood While shining a flashlight directly into the receiver window send the command R NOTE This test r
27. Space Message starts with a space Field 2 100 or 108 Heater state and error flags Field 3 2 450 2 550 Internal Reference voltage Field 4 9 00 36 00 Supply Voltage Field 5 11 15 Internal operating voltage Field 6 4 5 5 5 Internal operating voltage Field 7 11 15 Internal operating voltage Field 8 00 00 Not applicable in this check Field 9 00 00 Not applicable in this check Field 10 85 105 Transmitter power monitor Field 11 80 120 Forward Receiver monitor optional Field 12 80 120 Back Receiver monitor Not VPF710 Optional Field 13 00 99 Transmitter Window Contamination Field 14 00 99 Forward Receiver Window Contamination Optional Field 15 00 99 Back Receiver Window Contamination Optional Field 16 Temperature Field 17 3300 4200 ADC Interrupts per second Table 1 9 Remote Self Test and Monitoring Message Fields STEP 6 Test and Commissioning 29 Biral Sensor Set up L Section 1 30 Check that the values in the remote Self Test amp Monitoring message from the previous Data Transmission To Sensor Check are within the ranges indicated in Table 1 9 Remote Self Test and Monitoring Message Fields 1 6 Calibration Check The sensor is fully calibrated before it leaves Biral However if you would like to carry out a user confidence calibration check please follow the calibration check procedure in paragraph 5 1 page 61 to ensure that the MOR value changes i e the sensor responds
28. ati i rene nere Rte ri t dee 28 Checking Power Supply deed does eie ae Fade eeu uae 28 Remote Selt T st Check Bg de echte be Enea es 29 Deli Pest Codes est ERI e ERN ARRAS 55 sensor RESPONSES oce e eoe Petite e I Sec ert E dye re M i te 53 Sensor Self Test Capabilities ecrit tete tette tfe ratae to enn dote einn 97 V VISIBILITY MEASUREMENT SPECIFICATION eese nennen tenete ener nennen enn 87 89 XPETIO DATA MESSAGES Reed ds cab i o e a old 32 MPP730 DATA MESSAGES e ERE rt RESP E RERO UE RN EAE REM ER S RE EFI 34 VPE750 DE 39 W WARRANTY dr eben et d vir 28 WEATHER STATION MODULE 3 38 WINDOW CLEANING E ERR ER RENE e D ERO ERR TENER REO TREAT 55 WINDOW HEATERS 5 54 WINDOW MONITOR CHECKS be eden ree ee d e ton der ee ue RU ERN EOM SERE 58 WMOQO FPABLE A ote LO EE E e erue ie d re 34 39 42 91 104 Index Biral Section 9 Notes 9 NOTES 105 2 N Biral Ts
29. before site installation This is to ensure that you are comfortable with the functionality of the sensor and to pre empt any queries that arise before attempting site installation Note this procedure assumes a default configuration for the sensor please check the Calibration Certificate supplied with your sensor for specific configuration details NOTE In this test and in all subsequent sections of this manual the following convention MUST be observed ALL COMMANDS SHOULD BE TERMINATED WITH lt CARRIAGE RETURN gt AND lt LINE FEED gt ASCH CHARACTERS 13 AND 10 In this manual this is normally abbreviated to lt CRLF gt Equipment Test Procedure 1 Connect the power input cable to a local power source do not turn power source on Connect sensor earth lug to earth this may not be necessary but can help prevent communication errors with certain PCs 2 Connect the signal cable to a PC running Sensor Interface Software If this is not available use a terminal program for example Windows Hyper Terminal For RS422 485 sensors a RS422 to RS232 converter must be used Note Biral recommends testing to be done with RS232 or RS422 as applicable When you are confident that the sensor is working it can then be set up for RS485 if required 3 Configure the terminal program either Biral Sensor Interface Software or Hyper Terminal as follows Default Interface Parameters Baud Roles
30. can only be supplied configured for RS232 data communication option and only in the 12V DC or 24V DC models Note For RS232 data configuration cable lengths above 6m will not work reliably at high baud rates It is strongly recommended that baud rates no higher than 4800 are used for cable lengths up to 25m All the cables are supplied terminated at one end with the applicable military style connectors with metal coupling nuts Contacts in the plugs and receptacles are gold over nickel plated copper for maximum corrosion resistance Internal gaskets assure watertight performance The cables are terminated with tinned tails at the other end for user connections Each connector configuration is specific to its sensor function so that each can only be mated to the correct cable An option for the cables to be permanently connected to the sensor via cable glands is available see paragraph 1 2 7 1 2 22 Sensor Connections VPF710 and VPF730 Temperature Sensor 3 Socket Data Cable RS232 RS422 or RS485 Signal 6 Pin Power Input 3 Pin Figure 1 2 Example of VPF710 and VPF730 Connectors STEP 2 Electrical connections Biral Sectional Sensor Set up Figure 1 2 Example of VPF710 and VPF730 Connectors shows the base of a typical sensor The sensor will only be fitted with the required connectors so the actual number and position of the connectors may not be as shown The cables suppl
31. cleaning recommended required F Windows contaminated fault O Sensor not reset since last R command X Sensor reset since last R command 444 44 Total EXCO km lt es gt If selected this will be the checksum character The checksum is off by default Table 2 4 VPF730 Expanded Data Message Two typical expanded data messages from a VPF730 are as follows PW01 0060 0000 000 42 KM NP FG 00 41 00 0000 013 0 C 0000 007 12 007 12 026 17 0001 000 000 007 12 PW01 0060 0000 000 42 KM NP FG 00 45 00 0000 012 5 C 0000 007 12 007 12 026 18 0001 000 000 007 12 Data Output Message VPF730 37 Biral Standard Operating Data 8 2 2 3 Data Message Variations For ALS WSM VPF710 and VPF730 For sensors fitted with an Ambient Light Sensor or Weather Station Module data output strings are identical to the standard message with the following appended to the message prior to the optional check sum lt cs gt and the carriage return and line feed lt crlf gt 2 3 1 Weather Station Module EXT aaaa bbbb cccc dddd Message Maning EXT Optional external inputs aaaa WSM Channel 1 0000 0 00V 1000 10 00 bbbb WSM Channel 2 0000 0 00 1000 10 00 WSM Channel 3 0000 0 00V 1000 10 00 dddd Not used Table 2 5 Message Extension for WSM 2 3 2 Ambient Light Sensor ALS t aaaaa bbb Mes
32. controlled by the Options Word setting see Table 1 6 Options Word lower byte To enable Date and Time stamp The sensor can be configured to generate messages with the date and time string by setting the least significant bit in the options word Step 1 Send the command CO Step 2 Send the command Note to enable checksum and time date stamp send OP100001 PLEASE BE EXTREMELY CAREFUL IN SETTING THE CORRECT BIT IN STEP 2 AS SETTING THE WRONG BIT WILL RESULT IN THE SENSOR FUNCTIONING INCORRECTLY To check the setting of the options word send the command OP The sensor should respond 00000000 00000001 To disable Date and Time stamp To disable the date and time stamp send the command in step 2 above To read the current Date and Time Send the command TR The sensor will respond with the date time message e g 2 STEP 4 Configuration Options Sensor Set up 1 section 1 12 FRIDAY 23103112 13 15 25 000 To set the current Date and Time There are two commands required to set the current date and time SD sets the real time clock date The format of the command is SDWDDMMYY where W is the day of the week 1 7 with Sunday being 7 DD is the date 01 31 MM isthe month 01 12 YY is the year 00 99 The sensor will respond with ST sets the real time clock time The format of the command 1 STHHMMSS where HH is the hours
33. in 24 hour clock 00 23 is the minutes 00 59 SS is the seconds 00 59 The sensor will respond with 1 4 3 Checksum to verify message A check sum byte can be included with messages sent by the sensor to verify that noise in the communications link has not changed the message Generally noise is not a problem and checksum verification is not required This is controlled by the Options Word setting see Table 1 6 Options Word lower byte Note if RS485 communications are selected then this checksum is not used By default the sensor is configured at the factory with checksum DISABLED To enable checksum The sensor can be configured to generate messages with a check sum byte by setting the sixth bit in the options word STEP 4 Configuration Options I Biral Section Sensor Set up Step 1 Send the command CO Step 2 Send the command OP100000 Note to enable checksum and time date stamp send OP100001 PLEASE BE EXTREMELY CAREFUL IN SETTING THE CORRECT BIT IN STEP 2 AS SETTING THE WRONG BIT WILL RESULT IN THE SENSOR FUNCTIONING INCORRECTLY To check the setting of the options word send the command OP The sensor should respond 00000000 00100000M NB M is the checksum character To disable checksum To disable the checksum send the command in step 2 above The check sum is positioned after the
34. may not provide the U bolt with adequate bearing surface Note Pipe sizes often refer to their inside diameter some 60 mm ID pipe may be too large for the U bolts to fit around A stainless steel closed circle U bolt with hardware 1s provided for securing the sensor to the top of the mast A V block saddle is attached to the sensor head mounting plate to oppose the U bolt thus providing a secure grip on the mast The sensor head should be mounted near the very top so that the mast will not interfere with the free flow of fog or precipitation through the sample volume The flat stainless steel washers should be placed next to the anodised surface of the mounting plate to prevent gouging by the lock washers as the nuts are tightened Figure 1 6 U bolt Mounting Method 24 STEP 5 Installation Biral Section ATT Sensor Set up 1 5 5 Mounting the Sensor VPF750 Specific The VPF750 consists of a VPF 730 Present Weather Sensor combined with a Precipitation Sensor a Precision Temperature and Humidity sensor with radiation shield and an optional Ambient Light Sensor The complete system is assembled as shown in Figure 1 7 VPF750 System Precipitation Sensor VPF730 Present Weather Sensor Temperature and Humidity Sensor Ambient Light Sensor Figure 1 7 VPF750 System STEP 5 Installation 25 Sensor Set up Section 1 26 1 5 6 Assembly Instructions VPF750 On the
35. measurement of visual range in heavy haze and fog Such transmissometers prove to be accurate calibration references only over a limited range of visibilities namely 1 2B to 20B where B is the baseline of the transmissometer A typical airport transmissometer has a baseline in the neighbourhood of 100 meters Thus its range of valid measurements extends from 50 meters to 2000 meters This range encompasses only two environmental conditions fog and very heavy haze To assure that the fog calibration of HSS sensors remains valid for lighter haze conditions and clear air extensive use has been made of visual observations and televisiometer measurements Proper targets for such observations must satisfy the conditions required by daytime visual range formulae 1 e large dark objects silhouetted against the horizon sky with no cloud cover present A minor wavelength dependence effect is present for haze measurements which is discussed later 6 4 3 Visibility During Precipitation Itis highly desirous that the fog haze calibration of a FSM carries over to various forms of precipitation For this condition to be satisfied requires that the measurements of a fog haze calibrated FSM give identical results to a transmissometer in snow and rain Forward scatter meters configured for a central scattering angle of 35 degrees and calibrated against transmissometers in fog haze environments will overestimate the visibility in snow and underestimate t
36. message Send command 00D FF Recommendations When using the sensor an RS485 network it is recommended that the sensor be set up in polled mode Automatic message transmission disabled rather than transmitting a data message automatically See paragraph 1 4 7 for full instructions for setting this configuration NOTE When RS485 communications are enabled the sensor will not output the Biral Sensor Startup message on power up and reset 1 4 7 Automatic message setting The sensor can be set to send a data message automatically after each data collection period or to send a data message only when requested polled sensor The default setting 1s for automatic data transmission To check which method is programmed send the message OSAM The sensor will send the reply 00 Automatic message transmission disabled 01 Automatic message transmission enabled To set the sensor to the required automatic message setting send the message OSAMx Where x is 0 Automatic message transmission disabled 1 Automatic message transmission enabled The sensor will respond with OK STEP 4 Configuration Options 17 Biral Sensor Set up section 1 18 1 4 8 Data message type setting The sensor can be set to send a compressed data message or an expanded data message as detailed in section 2 The default setting is for expanded data message To check which message is programmed send the message OSC
37. message and before the end characters lt crlf gt The check sum value is between 0 and 127 and is the sum modulo 128 the remainder after the sum is divided by 128 of all the ASCII values of the characters in the message except the end characters The check sum value is replaced by its bit wise complement if it happens to be any of the following ASCII 8 backspace ASCII 10 linefeed ASCII 13 carriage return ASCII 17 through ASCII 20 through DC4 or ASCII 33 exclamation point For Message Cm lt cksum gt lt crlf gt The calculation is as follows lt cksum gt gt c MODI28 n l IF cksum 8 THEN lt cksum gt 119 IF lt cksum gt 10 THEN lt cksum gt 117 IF lt cksum gt 13 THEN lt cksum gt 114 IF lt cksum gt 17 THEN lt cksum gt 110 IF lt cksum gt 18 THEN lt cksum gt 109 IF lt cksum gt 19 THEN lt cksum gt 108 2 STEP 4 Configuration Options 13 Sensor Set up c L Section 1 14 IF lt cksum gt 20 THEN lt cksum gt 107 IF lt cksum gt 33 THEN lt cksum gt 94 1 4 4 Communications Configuration TheVPF700 series sensor can use either RS232C or RS422 RS485 signal voltage levels The configuration of the sensor is selected when ordering since the change in protocol and line drivers involves changes to internal wiring Check with the delivery paperwork to confirm the required configuration The configuration betwe
38. of VPF710 and VPF730 Connectors 4 Figure 1 3 VPF750 Connectors 5 Figure 1 4 VPF710 Orientation 23 Figure 1 5 VPF730 and VPF750 Orientation 23 Figure 1 6 U bolt Mounting 24 Figure 1 7 VPF750 ener a enne 25 Figure 1 8 Precipitation Sensor Mounting 26 Figure 5 1 Assembly of Calibration Reference 62 Figure 6 1 Sensor Sample Volume essere 68 Figure 6 2 Effects of Atmosphere on Perceived Brightness of Target Objects 69 Figure 6 3 Precipitation Matrix sessi 80 Figure 6 4 VPF730 Sensor Functional Block Diagram 2 2 2 81 Figure 7 1 VPF730 Model Dimensions mm essen 99 Table 1 1 AC Power Connections essent eene 5 Table 1 2 DC Power 6 Table 1 3 RS232 Signal Connections 6 Table 1 4 RS422 485 Signal Connections sese 6 Table 1 5 Combined Power and Data Connections 7 Table 1 6 Options Word lower 10 Table 1 7 Baud Rate 20 Table
39. to changes in visibility THIS PROCEDURE CAN ONLY BE COMPLETED IF A SUITABLE VPF700 SERIES CALIBRATION KIT IS AVAILABLE CONGRATULATIONS YOUR SENSOR SHOULD NOW BE FULLY CONFIGURED TESTED AND INSTALLED READY FOR USE THE REMAINDER OF THIS MANUAL COVERS STANDARD DATA MESSAGES COMMANDS AND RESPONSES OPERATIONAL AND MAINTENANCE PROCEDURES CALIBRATION CHECK AND RE CALIBRATION PROCEDURE MEASUREMENT PRINCIPLES SENSOR DETAILS AND SPECIFICATIONS STEP 6 Test and Commissioning B ira 2 Standard Operating Data 2 STANDARD OPERATING DATA When in standard mode a data message will be output from the sensor every measurement period default 60 seconds When in polled mode the same message is output only in response to the D command The operating mode is checked by sending command OSAM standard mode default is selected if the response is 01 If the response is 00 the polled mode is selected Instructions for setting this configuration are provided in paragraph 1 4 7 page 17 For each model in the VPF700 series of sensors either a compressed data message or an expanded data message can be selected The type of message is checked by sending command OSCM The expanded data message default is selected if the response is 00 If the response is 01 the compressed data message is selected Instructions for setting
40. within this manual require the use of a PC or equivalent To achieve the two way serial communication required Biral recommends the use of a PC running the Biral Sensor Interface Software If this software is not available use a terminal program for example Windows Hyper Terminal M The Sensor Interface Software is available from our website www Biral com or contact Biral at Info Biral com Sensor Set up 1 Biral Sensor Set up Section 1 1 1 STEP 1 Unpacking the sensor Documentation Cables and Mounting Kit Calibration Kit Option Top Layer VPF730 shown Other sensors will be packed similarly Spaces for any Optional Accessories e g ALS Bottom Layer Figure 1 1 VPF730 in its packaging 2 STEP 1 Unpacking the sensor Biral Section 1 _ TTT Sensor Set up Other optional components you may have ordered Calibration Kit The calibration kit is supplied in a protective carrying case containing a calibration screen mounting arm and connector referred to as the calibration reference plaque when assembled and 3 x grey foam plugs these are the ZERO PLUGS referred to in the calibration sections Transit Case A rigid re usable transit case designed to provide full protection to the instrument for regular shipping Please note if this is not ordered the sensor is shipped in the standard rugged foam filled box as shown in Figure 1 1 VPF730 in its packaging Ma
41. 1 000 00 0102 000 0160 45 Data Output Message 750 Biral Standard Operating Data lt 2 243 METAR Codes Code METAR Number Code zoe XX Not Ready first 5 minutes from restart 00 No significant weather observed or sensor starting 04 HZ Haze visibility greater than or equal to IKM 04 FU smoke visibility greater than or equal to IKM 04 DU Dust visibility greater than or equal to 10 BR Mist only available with separate temperature and humidity sensor as analogue input 20 Fog in last hour but not at time of observation 21 Precipitation in last hour but not at time of observation 22 Drizzle in last hour but not at time of observation 23 Rain in last hour but not at time of observation 24 Snow in last hour but not at time of observation 25 Freezing Drizzle Freezing Rain in last hour but not at time of observation 30 FG Fog 31 Fog in patches 32 PRFG Fog becoming thinner in last hour 33 FG Fog no appreciable change in last hour 34 FG Fog begun or becoming thicker in last hour 35 FZFG Freezing Fog 40 UP Indeterminate precipitation type 51 DZ Drizzle not freezing slight 52 DZ Drizzle not freezing moderate 53 DZ Drizzle not freezing heavy 54 FZDZ Drizzle freezing slight 55 FZDZ Drizzle freezing moderate 56 FZDZ Drizzle freezing heavy 57 RADZ
42. 1 8 Recommended Sensor Height Above 22 Table 1 9 Remote Self Test and Monitoring Message Fields 29 Table 2 1 VPF710 Compressed Data 32 Table 2 2 VPF710 Expanded Data 34 Table 2 3 VPF730 Compressed Data 35 Table 2 4 VPF730 Expanded Data 37 Table 2 5 Message Extension for 38 Table 2 6 Message Extension for 8 4 0 4 1 38 Table 2 7 VPF750 Compressed Data 41 Table 2 8 VPF750 Expanded Data Message sse 44 Table 2 9 METAR Codes erre eere 47 Table 3 1 Commands for VPF700 Series of 50 Table 3 2 Command Response esses enne 5 Table 3 3 Command T Response esses ener 52 Table 3 4 Responses From Sensor ene 53 Table 7 1 Measurement Capabilities of the VPF700 Series of Sensors 87 Table 7 2 Additional Measurement Capabilities of the VPF730 and VPF750 88 Table 7 3 Additional Precipitation Obstruction to Vision VPF750 88 Table 7 4 Past Weather determination Types 750
43. 8 89 93 PRESENT WEATHER 2 E EE DEN UR T RR E ERR pe den sete spa 86 PRESENT WEATHER CODES MEE TAR edge e et ete e b aede dee 46 47 WMO Table4680 12 5 de Ape eee db d been ha 91 93 PRODUCT OVERVIEW d DRE reo duces ero ta eee e ER ERG RHENO 82 R REMOTE SELF TEST amp MONITORING 82 29 IBI I 9 29 RESPONSES FROM SENSOR 53 M ete et t eti to ee MH M ten 52 To Command eo nete ce OHIO HER 51 Fo Gorman 1 25 52 RS232 desecrated dese ayn 4 6 7 8 28 84 hM racine rade clea 6 8 14 28 96 A EE d 6 8 12 28 48 96 Configuration Setin ES 1 1 i 14 17 S SELF TEST amp MONITORING sese enn eee ener SEE REMOTE SELF TEST amp MONITORING TEST CODES Doi deo tne 55 SENSOR COMMANDS a er AATE aO n eere Usu edere 48 SENSOR CONNECTIONS
44. 97 Product Overview gt 2 gt gt gt Section 7 98 Forward Scatter Receiver Window Contamination Back Scatter Receiver Window Contamination Power Supply Voltages Non Volatile Memory Check Sum Test EPROM Check Sum Test Restart Occurrence Sensor Sample Interrupt Verification RAM Read Write Verification Register Read Write Verification A D Control Signal Test A D Conversion Accuracy Check Input Voltage Check Battery Check on DC Powered Sensors Only Forward Scatter Background Illumination Level Back Scatter Background Illumination Level Standard Self Test and Monitoring is a Standard Feature on the VPF700 Series of sensors Advanced Self Test and Monitoring is an Optional Accessory on the VPF700 Series of Sensor Specifications Biral Section 7 i __ Product Overview 7 5 700 Series of Sensors Dimensions The model shown is the VPF730 and VPF750 The VPF710 is identical except that the Back Scatter Head is not fitted Back Scatter Head 751 Figure 7 1 VPF730 Model Dimensions mm VPF750 is identical VPF700 Dimensions 99 Biral Section 8 8 INDEX ACCESSORIES 58 d 84 Ambient Sensors Eee d a i tee RR d 85 Calibration Kita iter etre tree 84 High Accu
45. B Back Scatter Receiver Flooded with Light T Temperature Humidity sensor Fault O Windows not contaminated X Windows contaminated cleaning recommended required F Windows contaminated fault O Sensor not reset since last R command X Sensor reset since last R command 40 Data Output Message VPF750 Section 2 Standard Operating Data Message Meaning teeeee ALS signal 1 minute average value cd m fff ALS Self Test and Monitoring see paragraph 4 2 Other self test values OK X Other self test fault exists O Window not contaminated X Window contaminated cleaning recommended required F Window contaminated fault S Sensor input saturated O Sensor not reset since last R command X Sensor reset since last R command If selected this will be the checksum character checksum is off by default Table 2 7 VP F750 Compressed Data Message Two typical compressed data messages from a VPF750 are as follows CP 001 52 09 30 KM 00 0426 008 6 000 00071 000 CP 001 62 09 87 KM 00 0612 008 6 000 00102 000 Data Output Message VPF750 41 Standard Operating Data Section 2 242 750 Expanded Data Message The data message format is lt Date gt lt Time gt VPF750 nnn xxxx aa aa KM cc w1 w dd eeeee fff fff oo oo KM
46. M The sensor will send the reply 00 Expanded data message enabled 01 Compressed data message enabled To set the sensor to the required data message setting send the message OSCMx Where x is 0 Expanded data message enabled 1 Compressed data message enabled The sensor will respond with OK 1 4 9 Optional hood heater operating setting The sensor can be set to have the hood heaters disabled or for them to work automatically The default setting for sensors with fitted hood heaters is for automatic hood heater operation To check which configuration is programmed send the message OSHH The sensor will send the reply 00 Hood heaters disabled 01 Hood heaters on automatic To set the sensor to the required hood heater configuration send the message OSHHx Where x 15 0 Hood heaters disabled 1 Hood heaters on automatic The sensor will respond with OK 1 4 10 Window heater operating setting The sensor can be set to have the window heaters disabled permanently enabled or for them to be controlled according to contamination levels The default setting 18 for window heaters enabled and on To check which configuration is programmed send the message OSWH The sensor will send the reply 00 Window heaters disabled STEP 4 Configuration Options Section 1 01 Window heaters enabled and 02 Window heaters enabled and controlled according to contamination levels
47. ONS OF SENSOR oiai ctos co suns do eaa dea aea cease dea aede eae aa e eaa 99 E BEBCTRIGAL CONNECTIONS n deo ee oto dta a eter a ks 4 ENVIRONMENTAL SPECIFICATION 96 roO RE EET EV EH E OE ERI 8 EXCO CALIBRATION CHECK i ee eee ette coc ea eee eth do eed odo sed ana do conta 58 EX CORP CALIBRATION b als ite rer vie 64 G GLANDED CABLE OUTLET Shins e 7 Eia ae 54 54 84 PE NR 48 State and Error Elags 5 6 dee eode e cider D e de keen oan Gane Aves 51 Window heaters de misters eese eerte nete enne nennen ten ene eterne eene 54 HSS idend teo abbas ad e det 3 36 57 85 IDENTIFICATION NUMBER aoeeoe eene eE EEE A EAE EE AE E PARET E AE AAA E EE EAEN Aia 48 INSTALLATION E A ERE ER ee ee Re RE Ha a 21 Electrical 27 Height Above Ground ceder m Pe t d e de p e rb terae led 21 Mounting 24 25 VPF700 Dimensions 101 Biral Index Section 8 0 C 22 Sititig
48. RIDAY TR 1 4 2 The final 000 is an internal fixed 23 03 12 v fv constant 13 15 25 000 SDWDDMM Set current date See paragraph 1 4 2 OK STHHMMSS Set current time See paragraph 1 4 2 OK y y WT Send current Window xx 4 4 threshold for warning indication 49 Sensor Commands Biral Commands and Responses Section 3 Command Function Response 710 730 750 Set window contamination threshold for a warning indication transmission WT fv Range 0 to 30 Calibration must be enabled Default 10 o Bx Set communication baud rate See para N 1 7 1 4 11 50 Table 3 1 Commands for VPF700 Series of Sensors Sensor Commands Biral Sections Commands and Responses 3 1 1 Command R Send Remote Self Test and Monitoring Message Example response 2 509 24 1 12 3 5 01 12 5 00 00 00 00 100 105 107 00 00 00 021 0 4063 The various fields in the response as follows Field 1 Space The message starts with a space Field 2 ABC Heater state and error flags 1 Window heaters ON 2 De icer hood heaters ON 4 A D Control signal error 1 EPROM checksum error 2 Non volatile memory checksum error 4 RAM error Register error Ired commanded OFF Receiver test in progress Ired OFF 8 Sensor power reset since last
49. TED KINGDOM The customer is responsible for the shipping costs CE Certification Safety All Biral s HSS sensors comply with the requirements for CE marking Once installed it is the user s responsibility to ensure that all connections made to the sensor comply with all Local and National safety requirements In order for the mains version of any sensor to comply with the requirements of EN 61010 1 2010 Safety requirements for electrical equipment for measurement control and laboratory use the following should be observed A switch or circuit breaker must be included in the installation This switch or circuit breaker must be suitably located and easily reached It must be marked as the disconnecting device for this equipment vil Biral Sectional Sensor Set up 1 SENSOR SET UP The format of this section is such that it logically follows these recommended procedural steps Step 1 Unpack equipment and ensure that all required parts are supplied and identified Step 2 Make electrical connection as required for testing and configuration Step 3 Power up and test equipment on bench Step 4 Configure equipment as required for site installation Step 5 Installation including siting considerations height orientation mounting and electrical grounding Step 6 Carry out commissioning test procedure NOTE Many of the tests specified
50. To set the sensor to the required window heater configuration send the message OSWHx Where x is 0 Window heaters disabled 1 Window heaters enabled and on 2 Window heaters enabled and controlled according to contamination levels The sensor will respond with STEP 4 Configuration Options Sensor Set up 19 Biral Sensor Set up Section 1 1 4 11 Baud Rate Configuration Default communication parameters are 1200 Baud 9600 for VPF750 8 data bit 1 stop bit no parity and no flow control The baud rate may be changed if required as follows Send B Number Just typing B will bring up the different baud rate options SELECT REQUIRED BAUDRATE BY TYPING B NUMBER 1200 BAUD 2400 BAUD 4800 BAUD 9600 BAUD I9K2 BAUD 38K4 BAUD 57 6 BAUD Select the baud rate to use for example to select 9600 baud the user would type B4 lt CRLF gt The user then receives a prompt to send an OK to the sensor at the new baud rate setting The new setting will only be accepted if the user manages to communicate with the sensor at the new baud rate within 60 seconds Otherwise the sensor will reset and continue operation with the original baud rate settings If an OK command is received at the new baud rate the sensor will update its settings and restart Table 1 7 Baud Rate Configuration 20 STEP 4 Configuration Options Section
51. and data cable the cable furnished with the sensor has the following pin and conductor assignments The cable consists of 3 sets of twisted pairs The Function data refers to the SENSOR function Note this configuration is only available with the RS232 communication protocol used on a DC power supply sensor Pin Pair Conductor Function Number Number Colour A 1 Red ve DC B 1 White ve DC D 2 Brown Rx Data E 2 White Tx Data 3 Grey Signal Ground G 3 White Sensor Chassis Ground F Not Used Table 1 5 Combined Power and Data Connections 1 2 7 Option Glanded cable outlets Not available for the VPF750 sensor For extreme environments in particular continual salt spray even the MIL type passivated aluminium connectors can suffer serious corrosion over a few years Biral can provide a sensor with cables passing through plastic environmentally secure glands as a replacement for the standard connectors The cables in this option of the sensor are permanently connected to the sensor during manufacture The cables fitted will be as specified above See Table 1 1 AC Power Connections to Table 1 5 Combined Power and Data Connections for the connection details for the free end of the glanded cables STEP 2 Electrical connections Biral Sensor Set up Section 1 1 3 STEP 3 Equipment Test Biral recommends that the equipment is powered and checked on the bench
52. ated transients from high voltage plant located near to the sensor installation 1 5 2 Height Above Ground The optimum height at which to mount the sensor depends on the application The table below shows some recommended heights STEP 5 Installation 21 Biral Sensor Set up section 1 Application Typical height Comment Highway fog warning systems 1 5 to 2 meters Recommended height for the 4 9 to 6 6 feet sensor sample volume is the average distance of a vehicle driver s eyes above the roadway Airport applications 4 3 meters 14 feet This is the standard height for above the runway visibility sensors in the U S This height may differ in other countries General meteorological 1 8 meters 6 feet This is a suitable height unless the particular application dictates otherwise Table 1 8 Recommended Sensor Height Above Ground 1 5 3 Orientation of Sensor Head The orientation of the sensor head should be such that the rising or setting sun does not appear in the field of view of the receiver lens es It is desirable to avoid sunlight from flooding the receiver optics and to avoid sunlight induced noise spikes from creating false precipitation counts although false alarm algorithms in the sensors invariably eliminate such false counts 22 STEP 5 Installation Biral Section 1
53. aurora For purposes of Automated Present Weather Sensors the term present weather is restricted to those atmospheric phenomena that are local to the sensor These phenomena include 1 forms of liquid and frozen precipitation e g rain drizzle snow snow pellets snow grains ice pellets formerly sleet and hail 2 Those suspended particles that are classed as obstructions to vision namely mist fog haze dust and smoke Present Weather Measurements Biral Section 7 gt gt 5 Product Overview 7 3 0 Overview These sensors utilise microprocessor technology to perform automatic visibility precipitation not VPF710 and temperature measurements Both DC versions and mains driven versions of each sensor are available Patented techniques are employed to identify precipitation and to determine the presence of fog during episodes of precipitation 7 3 3 Visibility Related Measurements The measurement capabilities of the sensor are summarised in the table below Determination of visual range is based on measurements of the atmospheric extinction coefficient EXCO Note that EXCO includes the attenuating effects of both suspended particles and precipitating particles Meteorological optical range MOR is determined by application of the standard relation MOR 3 00 EXCO Haze and fog are the two most common forms of obstructions to vision In the absence o
54. backscatter receiver to aid in precipitation identification All models have the same time proven software for measuring visibility and precipitation type and performing remote self test diagnostics The measurement capabilities of these models are as follows Sensor Model Capability VPF710 Visibility VPF730 Visibility Precipitation type identification This model has an extra backscatter receiver for Rain rate Snowfall rate Precipitation accumulation 82 VPF700 Series of Present Weather Sensors Biral Section 7 TTT Product Overview VPF750 Visibility Precipitation type identification This model has an extra precipitation sensor and an extra high accuracy temperature and humidity sensor for 50 weather codes from WMO Code Table 4680 including Past Weather Freezing Rain Ice Pellets 7 12 Instrument Components Each sensor has been engineered and manufactured with high reliability components to provide accurate measurements under all weather conditions Its rugged anodised salt brazed aluminium construction is intended to serve you in the severest of environmental conditions throughout the long life of the instrument A VPF700 series sensor system consists of the major components listed below Item QUANTITY Basic Sensor assembly incorporating transmitter receiver and electronics housing 1 Stainless steel mounting U bolt kit for fixing to a pole 1 Cable Assemblies As Required Operat
55. cluding the colon character that begins the message and excluding the lt crlf gt pair at the end of the message The LRC byte is converted to 2 ASCII characters and appended to the message For example the message 42D Checksum is calculated as ASCII string 42D BYTE Values in HEX 3443244443F Sum is E9 One s compliment 0xFF OxE9 0x16 Two s compliment 0x16 1 0x17 Checksum is 0x17 Hex Checksum ASCII characters are 17 Transmitted string will therefore be 42D 17 lt CRLF gt e STEP 4 Configuration Options 15 Biral Sensor Set up section 1 16 End communications will end with the standard 2 characters carriage return line feed lt CRLF gt pair ASCII values of 0D amp hex 1 4 6 Sensor Addressing To use addressable RS485 communication each sensor must have a unique address in the range 0 99 By default the sensor address is set to 0 Querying the sensor address To query the sensor address send the command ADR The sensor should respond with the address e g 00 Changing the sensor address To change the sensor address send the command ADRxx where xx is a number between 00 and 99 e g ADRO2 sets the sensor address to 02 The sensor should respond with OK Enabling the addressable RS485 Communications The sensor can be configured to use addressable RS485 communications by setting the eighth bit in the options word see Table 1 6 O
56. demonstrated that this wavelength variation of extinction in haze is due to aerosol scattering and has a wavelength dependence of 1 o A const Others have shown this variation to be generally applicable for the spectral range from visible to near infrared wavelengths of 1 0 micron and for visibilities extending to 100 kilometres BIRAL FSMs operate at a wavelength of 0 88 microns because of the high powered IREDs available at that wavelength compared with LED s operating in the visible spectral region at the peak of the eye response 0 55 microns The variation with wavelength in haze implies that if two FSMS one operating at 0 88 micron and one at 0 55 micron are calibrated against a visible light transmissometer in fog then their measurement in haze will differ by the amount 2 Theory of Forward Scatter Meters 75 Biral Measurement Principles Section 6 6 5 76 13 o 0 88 oss 0 55 0 54 0 55 In fog and haze the visible light transmissometer will measure the total scattering coefficient 55 A visible light FSM might also give o 55 in haze but it does not because it measures the angular scattering coefficient not the total scattering coefficient Atmospheric aerosol models show in addition to the wavelength dependence a slight wavelength dependence of the phase functions as well For the two wavelengths of interest in the above example the phase func
57. distinguish between un scattered light and diffracted light and treats both as un scattered radiation As a result transmissometer measurements underestimate the total extinction coefficient There are two schools of thought regarding which sensor type gives the more valid visibility measurement in rain FSMs or transmissometers One school believes the eye performs the same function as the transmissometer receiver hence the transmissometer readings give the correct extinction coefficient The second school counters with the opinion that while the first argument may be valid for point light sources it is certainly not valid for non self Iuminous objects especially for the theoretical black target used in the definition of daytime visual range In the second case the target contrast is reduced by the air light that results from light scattered by the raindrop at all angles There is no light emanating from a black target to be diffracted toward the eye 6 4 4 Transmissometer Equivalent EXCO A BIRAL present weather sensor can satisfy either school of opinion using its unique measurement techniques For those that believe that the FSM measurements characterise the true extinction coefficient in rain the total EXCO value normally provided by the sensors is always available For the other school who believe that the true extinction coefficient in rain is that measured by transmissometers the BIRAL present weather sensors can provide the Transmiss
58. e Meaning 5 Slight Drizzle 52 Moderate Drizzle 53 Heavy Drizzle 61 Slight Rain 62 Moderate Rain 63 Heavy Rain 71 Slight Snow 72 Moderate Snow 73 Heavy Snow 89 Hail Transmissometer equivalent EXCO km dd dddd Amount of water in precipitation in last measurement period mm Temperature fff Self Test and Monitoring see paragraph 4 2 O Other self test values OK X Other self test fault exists O Windows not contaminated X Windows contaminated cleaning recommended required F Windows contaminated fault O Sensor not reset since last R command X Sensor reset since last R command lt cs gt If selected this will be the checksum character The checksum is off by default Table 2 3 VP F730 Compressed Data Message Two typical compressed data messages from a VPF730 are as follows 01 71 000 96 00 0048 005 4 000 01 71 000 11 00 0005 005 3 000 Data Output Message 730 35 Biral Standard Operating Data Section 2 2 2 2 VPF730 Expanded Data Message The data message format is lt Date gt lt Time gt P Waa bbbb cccc ddd dd KM eee ff gg gg hh hhhh ziii i C jjjj KKK kk IlI 1 2mmm mm nnnn ooo ppp qqq qq lt cs gt lt crlif gt Message Meaning lt Date gt Optional Date string in the form DD MM YY lt Time gt Optional Time string in the form HH MM SS PW Pre
59. eather sensors All these sensors have the necessary optimum configuration for accurate measurement of visibility in the densest of fogs to very clear air conditions They can detect the onset of precipitation not VPF710 as readily as a human observer and can measure the size and velocity of precipitation particles Unique patented techniques utilising precipitation size velocity distributions and backscatter forward scatter ratios provide high reliability identification of the type of precipitation False alarms and false identifications are kept to a minimum by the application of empirically derived algorithms sensitive to the characteristic of electronic noise and insects Also unique is the sensor s capability of separating the contribution of extinction due to precipitation from the total atmospheric extinction coefficient thus giving the sensor the capability to identify fog whenever it is simultaneously present during a precipitation episode In addition to its optimal and unique measurement capabilities the VPF700 sensors have a number of distinctive physical features Compactness Each sensor is a single package small in size and weight It can be readily installed by one person and can be used in portable or fixed installations Proven Software The basic software incorporated into the sensor has evolved over a long period of time and has been tested and proven in hundreds of sensors VPF700 Series of Present Weather Sensors
60. ed precipitation in mm EHE XXXX Accumulation time in minutes AC Clear accumulated precipitation OK y y ADR Send RS485 address See para 1 4 6 Set RS485 address ADRxx address oi J J d Range 00 99 See paragraph 1 4 6 BB Send instantaneous value of backscatter d EXCO Send instantaneous value of Total EXCO BL Vire y y less precipitation particle component BT Send instantaneous value of Total EXCO XXX XX y y Perform precipitation amount calibration A M Calibration must be enabled See para 5 4 Perform both forward scatter and CE backscatter Not 710 EXCO calibration Calibration must be enabled See para 5 2 N Y N Enable calibration OK Disable calibration OK Send latest data message See section 2 Turn hood heaters on temporarily If off at DHO time of command the heaters will turn off OK after 2 minutes for maintenance only Turn hood heaters off temporarily If on at DHX time of command the heaters will turn on OK after 2 minutes for maintenance only Set instrument identification number displayed in data message ID OK 710 730 Range x 1 to 99 Default 1 750 Range x 1 to 999 Default 1 48 Sensor Commands Biral Section 3 Commands Responses
61. efficient is converted to visual range by application of Visual Range Determination Biral 6 A Measurement Principles 1 Koschmieder s Law for daytime visual range 2 Allard s Law for night time visual range or 3 Variations on Koschmieder and Allard s Laws When an observer looks at a distant target the light from the target that reaches the observer is diminished by absorption and scattering the two components of extinction In addition to the light that originates at the target and ultimately reaches the observer extraneous light scattered into the line of sight by the intervening atmosphere is also seen by the observer It is this air light which we recognise as haze or fog The effect of extinction and added air light on the perceived brightness of visual targets is shown graphically below in Figure 6 2 Effects of Atmosphere on Perceived Brightness of Target Objects From this illustration we note that the apparent contrast between object and horizon sky decreases with increasing distance from the target This is true for both bright and dark objects BRIGHT OBJECT BRIGHTNESS OF HORIZON ei BLACK OBJECT RELATIVE BRIGHTNESS OBJECT OBSERVER DISTANCE Figure 6 2 Effects of Atmosphere on Perceived Brightness of Target Objects 6 2 Daytime Visual Range The origina
62. efinitions of precipitation intensity differ from the U S definitions it is possible for the sensor to be produced with the appropriate definitions installed BIRAL must be informed of this requirement at the time of order Drizzle Slight A trace to 0 01 inches 0 3 mm hour Moderate 0 01 inches 0 3 to 0 02 inches 0 5 mm hour Heavy More than 0 02 inches 0 5 mm hour Rain Slight A trace of 0 10 inches 2 5 mm hour Moderate 0 10 to 0 30 inches 2 6 to 7 6 mm hour Heavy More than 0 30 inches 7 6 mm hour Snow Slieht Visibility equal to or greater than 5 8 statute miles 0 55 nautical miles 1 000 meters Visibility 5 16 to 1 2 statute miles 0 25 to 0 5 nautical miles Moderate 500 to 900 meters Heav Visibility equal to or less than 1 4 statute miles 0 2 nautical miles y or 400 meters Frozen Precipitation other than snow Slight A trace to 0 10 inches 2 5 mm water equivalent hour Moderate 0 10 to 0 30 inches 2 6 to 7 6 mm water equivalent hour Heavy More than 0 30 inches 7 6 mm water equivalent hour 90 Table 7 5 US Precipitation Intensity Definitions Based on Federal Meteorological Handbook No 1 Part B 1 Present Weather Measurements Biral Section 7 Product Overview The following present weather codes from WMO Table 4680 are used on the VPF700 series of sensors Biral VPF710 Vis
63. emperature Effects lt 0 02 km Long Term Drift lt 0 02 km Precipitation Measurements Not VPF710 Biral Function Details Detection Threshold Rain 0 015mm hr 0 0006 in hr Detection Threshold 5 0 001 5mm hr 0 00006 in hr 20 Equiv Rain Rate Maximum 500mm hr 20 in hr Rain Rate Accuracy 10 Sensor Specifications 93 Product Overview Section 7 Maintenance Function Details MTBF Calculated 52 500 hrs 6 years Calibration Check 6 months recommended Clean Windows 3 months recommended dependent on environment Remote Self Test Monitoring Included VPF750 Specific Temperature and Humidity Measurements Response Time Function Details Humidity Type Capacitive Range 0 to 100 Relative Humidity Accuracy 2 Relative Humidity lt 20 seconds Temperature Type Range Response Time Accuracy 10 C to 40 C Accuracy lt 10 C gt 40 C PT 100 Class B 30 C to 70 C 0 2 C 0 2 C 0 0073 C C lt 20 seconds Table 7 6 Sensor Specifications 7 41 Instrument Characteristics Physical Function Details Scattering Angle Coverage 39 to 51 Sample Volume 400 cm Weight DC Sensors 5 6Kg Mains Powered Sensors 6 8Kg Length 0 75 m 94 Sensor Specifications Biral Product Overview
64. en RS422 and RS485 is user selectable The following paragraphs provide the instructions for this adjustment and details for setting up the RS485 communication if required 145 RS485 Configuration Any of the VPF700 series of sensors purchased with RS422 485 communication protocol can be set by the user for either RS422 or addressable RS485 communication protocols The software needs to be configured to use this protocol By default the sensor is configured at the factory for RS422 protocol unless specifically requested when ordering RS485 Protocol Format The RS485 communication protocol is based on the Modbus ASCII Frame Format Each data request and transfer is configured as follows Start 7 Sensor Address 2 Character address field Data As standard HSS message format see Section 2 LRC Checksum 2 Characters Longitudinal Redundancy Check End 2 Characters Carriage return Line Feed Start The colon symbol is used as start flag which is hex Sensor Address The 2 character address is defined by the operator for the unit and programmed as specified in the set up instructions Paragraph 1 4 6 It can be any numeric value between 00 and 99 It is used by the unit to define the recipient of the message and by the slave to define the source of the message STEP 4 Configuration Options 2 Section
65. ene eene 58 CALIBRATION ee esee esent seen saa setas ases 61 5 1 Calibration tette petatur onse Penna oe 61 5 2 Sensor Re calibrati n 64 5 3 Temperature Calibration Not 750 66 5 4 Precipitation Amount Calibration esses 66 MEASUREMENT 8 1 1 1 1 1 eee aestu ses etas es esas seen 68 6 1 Visibility Measurement Terminology essere 68 6 2 Visual Range Determination sese 68 6 3 Extinction Coefficient 2 2 71 6 4 Theory of Forward Scatter Meters essen 7 6 5 Precipitation Measurement esses 76 PRODUCT OVERVIEW cccssccssssssccsssssscccsssscccsscsscccsscssccesscssccsesssececescsssesssees 82 7 1 VPF700 Series of Present Weather Sensors 82 72 Sensor Feature S acs eoe ertet rere t 85 7 3 Present Weather 86 FIGURES TABLES Biral 7 4 Sensor Specifications ioter tee ek erbe tee 93 7 5 VPF700 Series of Sensors Dimensions 99 100 IAN LC M 105 Figure 1 1 VPF730 in its packaging essere 2 Figure 1 2 Example
66. equires the use of a filament bulb flashlight There is insufficient IR radiation from a visible LED source Verify that the value in the Forward Scatter Receiver Background Brightness field in the sensor response 1s much greater than 00 06 For the VPF730 and VPF750 repeat steps 1 to 6 but applying to the back scatter head and the Back Scatter Receiver Background Brightness field value in the sensor response User Confidence Checks Biral Sections gt Calibration Procedures 5 CALIBRATION PROCEDURES 5 1 This section explains how to CHECK the calibration of the sensor and ONLY IF NECESSARY how to recalibrate it ALL THE PROCEDURES IN THIS SECTION REQUIRE A VPF700 SERIES CALIBRATION KIT The Extinction Coefficient EXCO calibration of the forward scatter channel and the backscatter channel are checked by the procedure outlined below The Calibration Reference Plaque used for the calibration check has been assigned a forward scatter value which is a simulation of an EXCO expressed in kilometres This value is shown on the label which is attached to the arm of the calibration plaque This label also states the serial number of the calibration plaque to ensure that the correct plaque is used with that arm Each calibration plaque also has a backscatter value which although it also is expressed in kilometres is an artificial value assigned only
67. erence plaque from the sensor dismantle it and return it to its protective case for storage If the results of the calibration check have agreed with the value on the label attached to the calibration reference plaque within the above limits re calibration is NOT required A re calibration is required ONLY if the EXCO values are outside those on the calibration reference plaque AND the calibration check has been carried out ACCORDING TO THE CALIBRATION CHECK NOTES on page 62 5 2 Sensor Re calibration 64 RE CALIBRATING THE EXTINCTION COEFFICIENT SHOULD ONLY BE CARRIED OUT IF THE SENSOR HAS FAILED A CORRECTLY PERFORMED USER CONFIDENCE CHECK WARNING ERRORS DURING THIS RE CALIBRATION PROCEDURE WILL CAUSE THE SENSOR TO GIVE INCORRECT DATA BEFORE CONTINUING ENSURE THAT THE SENSOR 1 IS MOUNTED OUTSIDE AND THAT VISIBILITY IS GREATER THAN 10KM 2 HAS BEEN IN CONTINUOUS OPERATION FOR AT LEAST 1 HOUR 3 WINDOWS ARE CLEAN 4 IS NOT LOCATED NEAR A WALL OR OTHER OBSTRUCTION 5 IS NOT RECEIVING OPTICAL REFLECTIONS from surfaces or clothing Sensor Re calibration Biral Section5 Calibration Procedures Note All commands should be terminated with Carriage Return gt and Line Feed gt lt crIf gt see Paragraph 1 3 Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 Step 9 Set up the sensor with the calibration reference plaque in place
68. f precipitation the sensor determines the presence of haze or fog based on the MOR If the MOR is less than 1 km then fog FG is indicated in the output message If the MOR is between 1 and 10 km then haze HZ is indicated in the output message If MOR is greater than 10 km no obstruction to vision is indicated Visibility Measurements Function Details Meteorological Optical 10 metres to 75km 30 feet to 46 miles Range Atmospheric Extinction 300km to 0 04km Coefficient EXCO 2 at 2 km Accuracy 10 at 16 km 20 16 to 30 km 1 Identifies Fog or Haze precipitation absent Obstruction to vision 2 Identifies Fog in presence of precipitation Table 7 1 Measurement Capabilities of the VPF700 Series of Sensors Present Weather Measurements 87 Biral Product Overview Section 7 Precipitation Obstruction to Vision Measurements VPF730 and VPF750 Function Details a Liquid Precipitation 0 00025 mm min 0 00001 in min 0 015 mm hr 0 00060 in hr b Snow H20 Equivalent 0 000025 mm min 0 000001 in min 0 0015 mm hr 0 000060 in hr Identification Intensity Drizzle Slight Moderate Heavy Rain Slight Moderate Heavy Snow Slight Moderate Heavy Hail Precipitation rate Rain Up to 500 mm hr 20 in hr Snow Rain Equivalent up to 500 mm hr 20 in hr Obstruction to vision Haze Fog
69. for the purpose of checking that the sensitivity of the backscatter channel is within its proper limits This is not used for the VPF710 sensors Please see Figure 5 1 Assembly of Calibration Reference Plaque for a diagram of the Calibration Reference Plaque attached to a sensor Calibration Check The following instructions show you how to check the calibration of a VPF700 series sensor This procedure can only be completed with 1 VPF700 Series Calibration Kit 2 Connection to a PC running the Biral Sensor Interface Software or if this is not available terminal emulation software such as Windows amp Hyper Terminal This will use the signal data cable as provided If you need help with this please do not hesitate to contact us contact details on page vi Calibration Check 61 Calibration Procedures S Section 5 CALIBRATION CHECK NOTES PLEASE READ THESE NOTES BEFORE CONTINUING The EXCO Extinction Coefficient values depend heavily on the location and prevailing weather conditions and should only be carried out with the sensor MOUNTED OUTSIDE AND ON A CLEAR DAY VISIBILITY gt 10KM POWERED FOR AT LEAST 1 HOUR NOT LOCATED NEAR A WALL OR OTHER OBSTRUCTION NOT RECEIVING OPTICAL REFLECTIONS FROM SURFACES OR CLOTHING Assembly of the calibration plaque to the sensor The calibration reference plaque should first be attached to the arm Confirm that the serial number marked on the calibration refe
70. ftware If this is not available use a terminal program for example Windows Hyper Terminal For RS422 485 sensors a RS422 to RS232 converter must be used Note Biral recommends testing to be done with RS232 or RS422 as applicable When you are confident that the sensor is working it can then be set up for RS485 if required 3 Configure the terminal program as follows Default Interface Parameters Baud 1200 9600 on VPF750 Data aiino cere ape etg 8 Stop BIts 1 iod tpe toe ee ides None Flow tette None 28 STEP 6 Test and Commissioning Biral Section TTT Sensor Set up 4 Turn the local power source ON If communications are working the sensor will respond with Biral Sensor Startup 5 Check Data Transmission To Sensor Send the command R from the PC terminal to the sensor The sensor will respond with its remote Self Test amp Monitoring message For example see paragraph 1 6 3 for explanation 100 2 509 24 1 12 3 5 01 12 5 00 00 00 00 100 105 107 00 00 00 021 0 4063 6 Check Data Transmission From Sensor If the sensor is NOT in polled mode Wait for the sensor to transmit a Data Message approx 80 seconds from power up If the sensor is in polled mode send the command D from the PC terminal to the sensor A Data Message will be transmitted immediately 1 6 3 Remote Self Test Check Field 1
71. h Atmosphere University of Toronto Press Much post WWII work has substantiated the existence of this phenomenon Theory of Forward Scatter Meters Biral Section 6 Measurement Principles Many FSMs employ a 35 degree scattering angle configuration since this angle provides more scattered light hence more signal than do greater Loofah angles The phase function has an inverse dependence with increasing scattering angle its value being largest at smaller angles Whatever central angle is chosen for the FSM configuration there is no simple way of providing an absolute calibration for the FSM Calibration of a FSM must be accomplished by a comparison of measurements with an instrument that measures the atmospheric extinction coefficient directly A transmissometer is such an instrument Only one FSM of a given type usually the prototype need be calibrated against a well maintained visible light transmissometer The calibration of the prototype sensor is transferred to a calibration reference standard which then serves as the primary reference standard for calibration of all other FSMs of an identical configuration The primary standard for a given FSM is not a reliable reference standard for FSMS with any other size central angle types of optics or light source Well maintained transmissometers that are available for calibration purposes are airport type transmissometers dedicated to the
72. h a bright light source such as direct view ofthe sun This will affect the visibility reading and any precipitation readings If possible the sensor should be repositioned see paragraph 1 5 3 to prevent this occurrence This indicates a fault in the external temperature and humidity sensor Arrange for the temperature and humidity sensor to be serviced at the earliest possible opportunity The VPF750 will continue to work correctly as a visibility sensor with either this fault present or the temperature and humidity sensor disconnected It will also detect the presence of precipitation correctly but may provide incorrect precipitation type indications Self Test Codes 57 Maintenance Procedures Section 4 4 3 User Confidence Checks The following user confidence checks require bi directional communications with a PC running the Biral Sensor Interface Software If this is not available use a terminal program for example Windows Hyper Terminal 4 31 EXCO Calibration Check If you wish to carry out a user confidence calibration check please follow the calibration check procedure in paragraph 5 1 page 61 to ensure that the Exco value changes i e the sensor responds to changes in visibility THIS PROCEDURE CAN ONLY BE COMPLETED IF A SUITABLE VPF700 SERIES CALIBRATION KIT AND PC ARE AVAILABLE 4 3 7 Temperature Calibration Check Note temperature is not sho
73. h a VERY bright light source such as direct view of the sun Although the reported light level will be in error it can be implied that the true ambient light level is high 56 Self Test Codes Biral Section 4 Maintenance Procedures 4 2 3 Least Significant Character Other Self Test errors A variety of operating parameters are regularly checked against normal operational figures as an early warning of possible sensor faults This character indicates whether all parameters other than window contamination are normal This Self test code can be one of two characters O or X The VPF750 has an additional three possible codes F B and T These have the following meaning eX 750 only 750 only 750 only No Fault No action required Internal error Send command to list all internally monitored parameters Check against paragraph 3 1 1 to determine the cause of this error Send command RST to restart the sensor If the fault persists arrange for the sensor to be serviced at the earliest possible opportunity This indicates that the Forward scatter receiver is saturated with a bright light source such as direct view of the sun This will affect the visibility reading and any precipitation readings If possible the sensor should be repositioned see paragraph 1 5 3 to prevent this occurrence This indicates that the Back scatter receiver is saturated wit
74. h many years of reliable accurate operation Features of the HSS Sensors Full date time stamp in data string provided by the real time on board clock Flexibility to connect to a wide range of data collection processing units with a choice of RS232 RS422 or RS485 serial outputs Easy installation due to its light weight and small footprint Identification of precipitation type as well as accumulation totals Not VPF710 Identification of 50 weather codes from WMO Code Table 4680 VPF750 only There are currently three sensors in Biral s HSS sensor range These are the VPF710 the VPF730 and the VPF750 Throughout this manual the term VPF700 Series of Sensors is used to refer to features common to all three of these sensors Biral may introduce other HSS sensors based on the original HSS designs which fulfil alternative functions but do not form part of the VPF700 series and are not covered by this User manual Biral Customer Satisfaction At Biral we set our standards high and only your complete satisfaction is acceptable to us If you believe your experience has not met these standards we would be grateful if you would contact us so we can rectify any issues you may have equally if you have any positive experiences you would like to share After Sales Support Biral offers support by telephone and email for the lifetime of these sensors even if there has been a change of ownership so please get in t
75. he Federal Meteorological Handbook see Precipitation Measurements paragraph 7 3 4 Other reporting codes and intensities may also be provided to conform to local standards to determine the system in use please consult the calibration data supplied with the sensor When snow is identified the intensity is established on the basis of the visual range For other forms of frozen precipitation the intensity is established on the basis of the equivalent water content rate of fall Precipitation Measurements 79 Biral Section 6 Measurement Principles 8 umo er 31V9S A 1 1215 Y0313W0Y0AH 113013 U0313N0H0AH Figure 6 3 Precipitation Matrix General size velocity characteristics of various types of precipitation displayed on the precipitation recognition matrix Biral Precipitation Measurements 80 Measurement Principles Section 6 AHOWSK WSLSASENS 1 i I 1 t t t t HOSS320U8d H31H3ANO5 LINW I l 1 H31ndWO23 OL 1 i l l I i HaLNNOD od 03348 HOIH 1 1 HATIOHLNODOUSINW a
76. he visibility in rain To find out if there is a common Loofah angle for fog haze snow and rain HSS FSMs with central scattering angles other than 35 degrees have been operated for several years comparing their measurements with those of transmissometers in all types of Theory of Forward Scatter Meters 73 Biral Measurement Principles Section 6 74 weather The results indicate that with a scattering angle near 45 degrees a fog haze calibration will remain valid for snow There is no common Loofah angle that allows transmissometer measurements in rain to agree with those of a FSM The best result that can be achieved is a minimisation of the difference between the readings of a FSM in rain verses those of transmissometer Since FSMs give higher EXCOs in rain than transmissometers i e the corresponding visibilities are lower the difference is a fail safe error if one accepts the transmissometer readings as the true value Disagreement between FSMs and transmissometers in rain has two root causes 1 The phase function for scattering by rain is dramatically different from that of fog haze and snow the phase function has a highly forward directed diffraction component that accounts for one half of the light energy scattered by a raindrop and 2 The receiver of a transmissometer is unable to
77. hydrometeor size 0 5mm 52 Sensor Commands Biral Section 3 3 2 Sensor Responses Commands and Responses Response Meaning BAD CMD Your command was not understood by the sensor Check the text of the command and re send An error was detected in a character in the command Re send the COMM ERR command OK Command with no quantitative response was understood and executed TIMEOUT Command was sent with more than 10 seconds between characters Re send the command TOO LONG Command message was longer than 24 characters including end characters Re send the command Table 3 4 Responses From Sensor 53 Biral Sensor Responses Maintenance Procedures Section 4 4 MAINTENANCE PROCEDURES 4 1 54 The VPF700 series of sensors require very little maintenance The following sections detail the checks that are advisable to ensure continued good operation of the sensor The frequency of these checks depends upon the location and environmental conditions under which the sensor operates It is suggested that a general check plus window cleaning should take place typically at three monthly intervals This period may be increased or decreased dependent on the contamination determined during these inspections It is also recommended that a calibration check see paragraph 5 2 is carried out at six monthly intervals to verify that the instrument is still continuing t
78. ibility only no weather codes VPF730 Compressed message only 00 No significant weather observed or not ready 04 Haze or Smoke or Dust 10 Mist If optional high accuracy temperature humidity sensor fitted 30 Fog 40 Indeterminate precipitation type 5 Slight Drizzle 52 Moderate Drizzle 53 Heavy Drizzle 61 Shght Rain 62 Moderate Rain 63 Heavy Rain 71 Slight Snow 72 Moderate Snow 73 Heavy Snow 89 VPF750 Sensor not ready 00 04 10 20 21 22 23 24 25 30 31 32 33 34 35 40 51 No significant weather observed Haze or Smoke or Dust Mist Fog in last hour but not at time of observation Precipitation in last hour but not at time of observation Drizzle in last hour but not at time of observation Rain in last hour but not at time of observation Snow in last hour but not at time of observation Freezing Drizzle or Freezing Rain in last hour but not at time of observation Fog Fog in patches Fog becoming thinner in last hour Fog no appreciable change in last hour Fog begun or becoming thicker in last hour Freezing Fog Indeterminate precipitation type Slight Drizzle Present Weather Measurements 91 Product Overview 92 52 53 54 55 56 57 58 61 62 63 64 65 66 67 68 71 72 73 74 75 76 77 78 81 82 83 85 86 87 89 Moderate Drizzle Heavy Drizzle Freezing Slight Drizzle Freezing Moderate Drizzle Freezing Heavy Drizzle Drizzle and Rain Sligh
79. ied will be correct for the specific sensor and can only be mated with the correct sensor socket for each function 1 2 3 Sensor Connections VPF750 Temperature Humidity Sensor 6 Socket Power Input 3 Pin Precipitation Sensor 3 Socket Data Cable RS232 RS422 or RS485 Signal 6 Pin Ambient Light Sensor 7 Socket Figure 1 3 VPF750 Connectors Figure 1 3 VPF750 Connectors shows the base of a typical VPF750 sensor It shows the option of separate power and data connection the connection for the temperature and humidity sensor the precipitation sensor connection and the ambient light sensor connection The sensor will only be fitted with the required connectors so the actual number and position of the connectors may not be as shown Each ofthe items in the system is fitted with the appropriate plug which only fits the correct connector 1 2 4 Power Input Connections not combined power data cable see para 1 2 6 The power cable furnished with the sensor has the following pin and conductor assignments 110 and 230VAC Models Pin Number Conductor Colour Function A Brown AC Live B Blue AC Neutral C Yellow Green Sensor Ground Table 1 1 AC Power Connections 12 and 24VDC Models STEP 2 Electrical connections Biral Sensor Set up Pin Number Conductor Colour Function A Brown 12V DC or 24V DC B Blue OV Yellow Green Sensor Ground Table
80. iliary measurement sample period time between measurement of peripheral signals during measurement interval 2 to 20 seconds default 5 Not used Min window heat time in seconds when Operating State bits 7 and 8 01 Default 300 seconds Table 3 3 Command T Response 3 1 3 Command Send Precipitation message This responds by sending a precipitation matrix accumulated over the last five measurement periods This is a matrix of 16 rows with up to 21 readings each being the number of precipitation particles of that specific size and velocity Zeros to right are not displayed The meaning of the matrix is graphically presented in Section 6 Figure 6 3 Precipitation Matrix An example response which was during a period of heavy rain is provided below 001 1001 001 002 001 001 000 000 000 001 009 002 006 002 001 001 009 019 020 020 010 002 000 000 001 001 1011 033 068 078 056 042 020 005 001 000 001 003 031 048 041 047 033 038 027 014 009 008 003 004 007 027 020 013 016 011 007 002 008 006 007 004 000 005 006 005 007 003 000 002 003 001 000 000 000 001 000 000 006 004 005 000 001 002 001 000 000 001 000 001 007 000 005 002 001 000 001 000 000 001 000 001 000 000 000 001 000 000 000 000 001 1000 000 000 This shows the greatest precipitation amount in rows 5 and 6 relatively slow hydrometeor velocity 3 3m sec and in columns 2 to 8 relatively small
81. in a weather station system The data from these inputs is integrated into the standard VPF700 data output message see paragraph 2 3 1 Weather Station Module 7 1 4 Accessories Calibration Kit The calibration kit containing a reference standard calibration plaque in a protective carrying case is employed only at those times that the instrument calibration is being checked Transit Case A rigid re usable transit case designed to provide full protection to the instrument for regular shipping is available VPF700 Series of Present Weather Sensors Biral Section 7 gt 5 gt Product Overview 7 2 Biral Mains Adapter A mains adapter is available if required Ambient Light Sensor An ambient light sensor can be supplied as part of the VPF700 system This provides measurements of the ambient light intensity up to 40 000 Cd m with its output integrated into the standard VPF700 data output string See paragraph 2 3 2 Ambient Light Sensor for models VPF710 and 730 and paragraph 2 4 Data Output Message VPF750 External High Accuracy Temperature and Humidity Sensor Supplied as standard on the VPF750 Not applicable to the VPF710 When fitted to the VPF730 it enables Dust Smoke and Mist to be identified distinguishing these from Haze and Fog Sensor Features The VPF710 sensor is a visibility sensor The VPF730 and VPF750 are both visibility and present w
82. in the visibility Extinction Coefficient Calibration The calibration of the prototype sensor was carried out at the Weather Test Facility WTF of the Air Force Geophysical Laboratory which is located at the Otis Air National Guard Base ANGB on Cape Cod Massachusetts USA The calibration was made by comparison of atmospheric extinction coefficient measurements with those of standard FAA approved transmissometers Comparisons were made over an extremely wide range of fog and haze situations The calibration of each duplicate Present Weather Sensor is traceable back to the measurements made with the prototype instrument at the AFGL Weather Facility This primary calibration is transferred to other instruments of the same type using a primary reference standard whose equivalent extinction coefficient was established at the time of the primary calibration A secondary reference standard similar in construction to the primary standard can be furnished with each instrument so that the sensor calibration can be periodically checked The secondary reference standard has received its value of equivalent extinction coefficient by a comparison with the primary reference standard This determines the calibration constant for the secondary reference standard Theory of Forward Scatter Meters 6 4 11 Optical Sensor Configuration The visibility measurement capability of the VPF 700 series of sensors derives from its forward scatter meter FSM co
83. ins Adapter A mains adapter to operate a 12V or 24V sensor using mains power Ambient Light Sensor A very wide range greater than four decades background light meter that measures from 2 to 40 000 cd m This sensor connects via 1m cable to factory installed input on any of the VPF700 series of sensors Light levels are appended to the sensor data string as a 5 digit ASCII character string giving the luminance value in cd m see section 2 Weather Station Module 3 off 0 10V analogue inputs supplied with 1m interface cable Input levels are displayed in the data message see paragraph 2 3 1 External High Accuracy Temperature and Humidity Sensor Supplied as standard on the VPF750 Not applicable to the VPF710 When fitted to the VPF730 it enables Dust Smoke and Mist to be identified distinguishing these from Haze and Fog Bir al STEP 1 Unpacking the sensor 3 Sensor Set up Section 1 1 2 STEP 2 Electrical Connections All electrical connections should be completed before applying power to the sensor 1 2 1 Cables The VPF700 series of sensors are supplied with all necessary cables Generally two cables are required one for power and one for data These two cables are supplied in a standard length of 6m Any other length up to 25m can be supplied as an option if specified at time of order A single power and data cable can be supplied as an option if specified at time of order This single cable version
84. ion has caused the processor to reset This is generally of no importance but may assist in the diagnosis of any other problem which may have occurred previously 4 2 2 Central Character Window Contamination 700 series sensors have monitoring of contamination on the transmitter window Monitoring of the receiver window s is an option available at time of purchase The processor compensates the visibility reading to allow for this contamination and also checks each of the contamination figures against a value of either 10 default value or 30 This Self test code can be one of three characters O X or F dependent on the contamination reading s received These have the following meaning Window contamination is less than 10 Default value be adjusted by the user see command WTx paragraph 3 1 No action required X Window contamination warning The window contamination is between 10 and 30 The visibility reading provided is corrected utilising this contamination figure but it is recommended that the windows are cleaned at the earliest possible opportunity P Window contamination fault The window contamination is above 30 Although the visibility reading is still corrected using this contamination figure the accuracy may deteriorate as the contamination increases The windows require cleaning NOTE The ALS has an additional code of S This indicates that the sensor is saturated wit
85. ion and Maintenance Manual 1 The VPF750 has in addition Item QUANTITY Precipitation Sensor 1 High quality temperature and humidity sensors within a radiation shield 1 VPF700 Series of Present Weather Sensors 83 Biral Product Overview J __ Section 7 84 7 1 3 Optional Items Hood Heaters Heaters for the transmitter and receiver hoods These are to minimise any build up of ice within the optical paths They consist of 15W heaters per hood on all versions Advanced Self Test and Monitoring In addition to the standard self test transmitter window monitoring the sensors can have the optional receiver window monitoring to provide warning of additional contamination build up This option includes monitoring of the receiver sensitivities Single Cable for both Power and Data The sensor can be supplied with a single cable connector to carry both the power and data This can only be supplied for DC sensors with RS232 data configuration Customer Specified Cable Lengths The data and power cables can be supplied at any length up to 25m as specified by the customer Note For RS232 data configuration cable lengths above 6m will not work reliably at high baud rates It is strongly recommended that baud rates no higher than 4800 are used for cable lengths up to 25m Analog Inputs for Weather Station Integration The sensors can be supplied with three analog inputs designed for connection to other instruments
86. ipitation the sensor software measures the fraction of the atmospheric extinction coefficient due to precipitation and subtracts it from the total extinction coefficient to obtain a quantity we have named EXCO EVENTS If the value of EXCO EVENTS is greater than 3 00 then fog is declared to be present in addition to the precipitation as an obstruction to vision 7 3 4 Precipitation Measurements VPF730 VPF750 sensors identify three forms of precipitation namely drizzle rain and snow together with a wide variety of frozen forms of these VPF750 only Detection of the onset of precipitation is extremely sensitive being 0 00025 mm per minute for rain and approximately 0 000025 water equivalent mm per minute for snow Intensity of precipitation may be defined differently from one country to another In the United States the intensity of precipitation is defined differently for drizzle and rain than for snow For drizzle and rain the intensity slight moderate and heavy is based on the rate of fall of precipitation For snow the intensity is based on visual range unless fog is present In Present Weather Measurements 89 Biral Product Overview Section 7 classifying precipitation intensity the sensor utilises the precise definitions given in the Federal Meteorological Handbook These definitions are given in the tables below Table 7 5 Note If a sensor is intended for installation in a country where the d
87. itation in the hoods The operation of these heaters is dependent on the ambient temperature by default they are only switched on when the temperature is below 2 C They will then switch off when the temperature rises above 4 C When switched on it is easy to detect the heat from these heaters by placing a finger on the end of the hood When the temperature is above the switching temperature the heaters will be switched off but may be controlled using a PC running a terminal program such as the Biral Sensor Interface Software or Windows Hyper Terminal see page 1 The heaters may be switched on temporarily using the command DHO and off again using the command DHX The default setting is ON with automatic control These can be switched OFF permanently to save power if required See paragraph 1 4 9 for details 4 1 3 Window Cleaning A VPF700 series sensor is an optical instrument and is therefore susceptible to accumulation of contaminants on the windows in the hoods The windows should be cleaned by gently wiping the windows using a pure alcohol propanol and a soft cloth appropriate safety precautions must be taken when using pure alcohol All VPF700 series of sensors are fitted with a Transmitter Window monitoring system An equivalent Receiver Window monitoring system may be fitted as an option if required This monitoring system measures the optical contamination of the window and corrects the measured EXCO or MOR to compensate fo
88. ize distribution and the Gunn Kinzer measured velocities for raindrops in stagnant air were used to construct the matrix scales If rainfall behaved in the exact manner of the Marshall Palmer and Gunn Kinzer models all raindrop measurements would fall in the data bins along the diagonal of the Precipitation Recognition Matrix In practice several factors tend to disperse the size velocity relationship from the idealised characterisations 1 The Marshall Palmer size distribution for raindrops is only a best fit approximation 2 Winds and wind gusts can perturb the velocity size relationship 3 The shape of the sample volume can significantly influence the velocity size characteristics of particles 1 e Particles falling through a portion of the sample volume other than the centre or falling in other than a vertical direction because of wind will exhibit slightly different velocity size characteristics depending upon the shape of the sample volume and the direction of the wind For the foregoing reasons one expects raindrop counts to show up in some off diagonal bins of the Precipitation Recognition Matrix as shown in the schematic illustration given in Figure 6 3 Precipitation Matrix Indeed this conjecture is substantiated in practice This diagram shows a schematic portrayal of the use of the Precipitation Matrix to identify different kinds of precipitation The locations of various forms of precipitation which are schematically
89. l None Message Termination CR LF Message Check Sum Selectable 96 Sensor Specifications Biral Section 7 Product Overview Function Details Programmable Response to poll or Automatic at programmable intervals e g 30 seconds to several minutes 1 minute typical Instrument Identification Number Programmable Reporting Interval seconds Meteorological Optical Range Kilometres Precipitation Type Message Content Obstruction to Vision Fog Haze None Precipitation Amount One Minute Interval Temperature Remote Self Test amp Monitoring Flags Date and time tags Table 7 8 Digital Communication Interface Specifications 7 4 3 Sensor Remote Self Test Capabilities Standard Self Test and Monitoring Optical Source Power Transmitter Window Contamination Power Supply Voltages Non Volatile Memory Check Sum Test EPROM Check Sum Test Restart Occurrence Sensor Sample Interrupt Verification RAM Read Write Verification Register Read Write Verification A D Control Signal Test A D Conversion Accuracy Check Input Voltage Check Battery Check on DC Powered Sensors Only Forward Scatter Background Illumination Level Back Scatter Background Illumination Level Advanced Self Test and Monitoring Biral Optical Source Power Forward Scatter Receiver Sensitivity Back Scatter Receiver Sensitivity Transmitter Window Contamination Sensor Specifications
90. l formula for calculating daytime visual range VR that was formulated by Koschmieder in 1924 15 3 912 Va Where is the atmospheric extinction coefficient Visibility Measurement Terminology Visual Range Determination 69 Biral Measurement Principles Section 6 70 Subsequent investigations concluded that Koschmieder used too optimistic a value 0 02 for the liminal contrast threshold value of the human eye A liminal value of 0 05 is believed to be more realistic For the latter contrast threshold Koschmieder s Law is modified to become 3 00 Va Um This simple law accounts for both the extinction of light by the atmosphere and the addition of air light by the same atmosphere for a black target viewed against the horizon sky Thus the strict definition of daytime visual range implies the limiting distance at which a black target can be discerned against the horizon sky 6 2 2 Night time Visual Range Night time visual range refers to the distance at which an observer can see lights through the atmosphere at night Allard gave the formula for the distance at which lights of intensity I can be seen at night in 1876 Allard s Law is expressed as Where Et is the observer s illuminance threshold and is the atmospheric extinction coefficient In addition to the extincti
91. nfiguration Unlike a transmissometer which measures the total atmospheric extinction coefficient a FSM measures only an angular portion of the atmospheric scattering coefficient that is the scattering in a narrow range of angles around a central forward scatter angle The application of the standard universally accepted formulae for the calculation of daytime and night time visibility requires that the total atmospheric extinction coefficient be measured not the angular scattering coefficient Thus it is necessary to show that a measurement of the angular Visual Range Determination 71 Measurement Principles amp ection 6 72 scattering coefficient under certain strict conditions can be related to the total atmospheric extinction coefficient EXCO Where EXCO includes both scattering and absorption of radiation at all angles from 0 to 180 degrees and by all atmospheric constituents be they suspended aerosols precipitation or molecules of air The first step in that conversion process is to demonstrate that the total atmospheric scattering coefficient and total atmospheric extinction coefficient are synonymous for all practical purposes Assumption 1 The visibility measurements are restricted to less than 100 kilometers Rayleigh scattering by air molecules does not contribute significantly to atmospheric attenuation of visible light for visibility less than 100 kilometres Assumption 2 Absor
92. o perform within the specification Paragraph 4 2 Self Test Codes describes the meaning of the self test codes provided in all the standard data messages It specifies what actions if any are required to restore the sensor to full operational capability General Checks A general check of the physical condition of the sensor should be carried out at regular intervals Particular attention should be paid to the condition of the cables from the base of the unit 4 1 1 De mister Heaters fitted as standard to all sensors The window de misters are low powered heaters designed primarily to prevent condensation They maintain the temperature of the windows at a few degrees above ambient temperature The default setting is ON See paragraph 1 4 10 for details The warmth may be detected with the finger on the window but is easier to detect using a thermometer with surface temperature probe The windows should be between 5 and 10 C above ambient temperature after at least 10 minutes operation Ensure that windows are cleaned after coming into contact with the skin or other sources of contamination 4 1 2 Hood Heaters optional Hood heaters 1f ordered are fitted to the inside of each of the hoods 2 on the VPF710 and 3 on the VPF730 and VPF750 General Checks Biral Section gt gt gt Maintenance Procedures 4 2 The hood heaters are high power heaters to help prevent the build up of frozen precip
93. ometer Equivalent EXCO TEXCO The Transmissometer Equivalent EXCO is arrived at by the following steps Theory of Forward Scatter Meters Biral Section Measurement Principles 1 The sensor must first determine that the precipitation is rain not snow or other form of frozen precipitation 2 Separate the total EXCO into its components EVENTS EXCO and EXCO MINUS EVENTS This step is essential to remove the fog or haze component from EXCO 3 Using empirically determined relationship convert the FSM EVENTS EXCO to TRANSMISSOMETER EVENTS EXCO 4 Restore the EXCO EVENTS component i e non rain component of EXCO to arrive at TEXCO 5 Output EXCO EXCO EVENTS and TEXCO 6 4 5 Wavelength Dependence of FSM Measurements Measurements by forward scatter meters and transmissometers in fog have no wavelength dependence on the radiation employed by their light sources This fact is easily confirmed by the observation that fog is white in appearance Such is not the case with haze that has a decidedly blue cast in appearance The transition to fog from haze is not a gradual affair Middleton points to an abrupt transition in wavelength dependence at an extinction coefficient of 4 km This he takes to be the transition point from haze to fog Above 4 km there is no variation of the extinction coefficient with wavelength Below 4 km there is a distinct variation Angstrom
94. on of light by the atmosphere this formula accounts for the decrease of light from the point sources of light as the inverse square of the distance This formula for calculating night time visual range has a significant mathematical difference from the formula derived from Koschmieder s law Where the latter has a single algebraic relation between visibility and extinction coefficient the former has a transcendental relation between the two quantities Thus the solution can only be found by an iterative numerical procedure or from a prepared table of values 6 2 3 Meteorological Optical Range Meteorological Optical Range MOR is the length of the path in the atmosphere required to reduce the luminous flux in a collimated beam from an incandescent lamp at a colour temperature of 2700 K to 0 05 of its original value That is the length of the path is the atmosphere for which the regular transmittance is 0 05 Extinction Coefficient Calibration Theory of Forward Scatter Meters Biral 6 Measurement Principles 6 3 6 4 For practical purposes may calculate MOR the same manner as Daytime Visual Range MOR 15 given by the relation 3 00 MOR The use of MOR satisfies the requirements of a meteorologist since it yields a one to one correlation with atmospheric transmittance A change from day to night does not produce by itself a change
95. one end of the cable and left floating at the other end Preferably it should be attached to ground at the sensor end of the signal cable 4 Connections Use tight corrosion proof bare metal connections throughout the grounding system STEP 5 Installation 27 Biral Sensor Set up section 1 1 6 STEP 6 Test and Commissioning The following steps contain a few basic checks to provide confidence that the unit is functioning correctly after installation These checks are recommendations only and are neither essential nor exhaustive 1 6 1 Checking Power Supply Before connecting the power cable to the sensor the supply voltage being provided should be measured to ensure that the voltage present is compatible with the sensor power requirement Use a multimeter to measure AC DC voltage dependent on sensor voltage according to order For AC supplies check conformity with local and National installation requirements see CE Certification Safety page vii DANGER of electric shock Exercise caution when performing this measurement WARNING Only connect the power cable if it matches the voltage requirements of the sensor Damage caused by improper voltage connection is not covered under warranty 1 6 2 Checking Data link 1 Connect the power input cable to a local power source do not turn power source on 2 Connect the signal cable to a PC running the Biral Sensor Interface So
96. ot at time of observation 25 Freezing Drizzle or Freezing Rain in last hour but not at time of observation 30 Fog 31 Fog in patches 32 Fog becoming thinner in last hour 33 Fog no appreciable change in last hour 34 Fog begun or becoming thicker in last hour 35 Freezing Fog 40 Indeterminate precipitation type 51 Slight Drizzle 52 Moderate Drizzle 53 Heavy Drizzle 54 Freezing Slight Drizzle 55 Freezing Moderate Drizzle 56 Freezing Heavy Drizzle 57 Slight Drizzle and Rain 58 Moderate or Heavy Drizzle and Rain Biral Data Output Message VPF750 39 Standard Operating Data Section 2 Message Meaning 61 Slight Rain 62 Moderate Rain 63 Heavy Rain 64 Freezing Slight Rain 65 Freezing Moderate Rain 66 Freezing Heavy Rain 67 Slight Rain and Snow 68 Moderate or Heavy Rain and Snow 71 Slight Snow 72 Moderate Snow 73 Heavy Snow 74 Slight Ice Pellets 75 Moderate Ice Pellets 76 Heavy Ice Pellets Snow Grains 78 Ice Crystals 81 Slight Rain Showers 82 Moderate Rain Showers 83 Heavy Rain Showers 85 Slight Snow Showers 86 Moderate Snow Showers 87 Heavy Snow Showers 89 Hail aa aa KM Meteorological Optical Range KM bb bbbb Amount of water in precipitation in last minute mm Temperature Self Test and Monitoring see paragraph 4 2 O Other self test values OK X Other self test fault exists F Forward Scatter Receiver Flooded with Light
97. ouch if you require help Similarly if you have any questions about your new equipment we are only a mouse click or telephone call away Our contact details are on the following page NB For your convenience our contact details are also on the label fixed to your sensor Contacting Biral If you would like technical assistance advice or you have any queries regarding the operation of the sensor please do not hesitate to contact us For enquiries and technical support Contact us by telephone on 44 0 1275 847787 Contact us by fax on 44 0 1275 847303 Contact us by e mail at service biral com vi Biral Five year warranty The HSS Present Weather Sensors come with a Five year limited warranty against defective materials and workmanship If you have any questions about the warranty please contact Biral In order to help us to assist you please be sure to include the following information Model of equipment Serial number of equipment Nature of defect Data Output Strings Responses to R command Relevant application details Your full name address and contact details If you need to return the sensor The HSS sensors should give you many years of trouble free service but in the unlikely event that the equipment proves to be faulty and we have asked you to return the sensor to us please address the equipment to BIRAL Unit 8 Harbour Road Trading Estate Portishead Bristol BS20 7BL UNI
98. ption by fog natural aerosols and precipitation contributes a negligible amount of attenuation compared to their scattering for visible and near visible radiation Given the above reasonable assumptions the total scattering coefficient can be equated to the total extinction coefficient The next step in the process requires equating the angular scattering coefficient as measured by a FSM with the total scattering coefficient That transition requires restrictions to be placed on the physical configuration of a FSM and on the wavelengths of radiation employed 6 4 2 Visibility in Fog amp Haze The angular scattering coefficient be separated into two components a phase function 0 and the total scattering coefficient o as follows 0 0 To replace the total scattering coefficient by the angular scattering coefficient as required for valid measurements with a FSM it is obvious that the phase function must be a constant for all environmental conditions in which visibility measurements are of interest usually all weather conditions During WWII British scientists discovered a natural phenomenon that allowed substitution of the angular scattering coefficient for the total scattering coefficient In the scattering angle region between 35 to 55 degrees they found very little change in the phase function for all classes of fogs and hazes It was given the code name Loofah See W E K Middleton Vision throug
99. ptions Word lower byte Step 1 Send the command CO Step 2 Send the command OP10000000 Note to enable RS485 and time date stamp send OP10000001 PLEASE BE EXTREMELY CAREFUL IN SETTING THE CORRECT BIT IN STEP 2 AS SETTING THE WRONG BIT WILL RESULT IN THE SENSOR FUNCTIONING INCORRECTLY To check the setting of the options word send the command 000P FF The sensor should respond 0000000000 1000000073 NB 00 is the address and 73 is the LRC checksum character To disable RS485 Communications To disable the RS485 communications 1 revert to 5422 protocol send the command 000POFF in step 2 above or 00OP1FF to enable time date stamp STEP 4 Configuration Options 2 Section Sensor Set up NB 00 is the address and FF is the LRC checksum override character see below Checksum Override When using addressable RS485 communications the sensor will disregard any commands that do not have the sensor address or have an incorrect checksum When transmitting to the sensor all commands must be prefixed by where XX is the address and have the 2 character checksum on the end If the checksum character is set to FF then the sensor will accept the message without checking the checksum This is useful when using programs such as HyperTerminal for diagnostics For example A sensor with address 00 to request a data
100. r VPF710 the back scatter EXCO reported is within 5 of the Back EXCO value of the calibration plaque then the sensor is within its calibration limits The sensor can be returned to its operational configuration with confidence Remove the calibration reference plaque assembly from the sensor dismantle it and return it to its protective case for storage 5 3 Temperature Calibration Not VPF750 Note All commands should be terminated with lt Carriage Return gt and lt Line Feed gt lt crIf gt see Paragraph 1 3 Step 1 Step 2 Step 3 Step 4 Step 5 Send the command CO Sensor replies OK Send the temperature calibration command Sensor replies ENTER TEMP DEG C FORM XX X Enter the ambient temperature in C e g 19 3 Sensor replies CAL IN PROGRESS Almost immediately the sensor will send the message CAL COMPLETE The calibration process is complete 5 4 Precipitation Amount Calibration 66 Note All commands should be terminated with Carriage Return and Line Feed gt lt crlf gt see Paragraph 1 3 This process provides for adjusting the calibration factor of the sensor precipitation measurement The amount of adjustment to this factor is determined by making an independent measurement of the liquid accumulation over several rain episodes and comparing the accumulation reported by the sensor to this independently measured accumulation Precipi
101. r this contamination A warning is generated when the contamination reduces the signal by more than a pre set amount default 10 When this warning occurs the windows should be cleaned at the earliest possible opportunity If the contamination continues to increase up to a pre set limit of 30 the appropriate part of the remote maintenance and self test message in the sensor Data Output Message changes from X warning to F fault see paragraphs 2 and 4 2 2 The accuracy of the instrument if operated at greater contamination levels may begin to deteriorate The windows require cleaning as a matter of urgency Self Test Codes Self Test and Monitoring information is provided in all standard Operating Data Messages both of compressed and expanded formats This information consists of three alpha numeric characters which have the following meanings Bir al Self Test Codes 55 Maintenance Procedures 4 NOTE The command provides a response with full diagnostic information The extent of this information depends on the sensor configuration specified at time of purchase This response is detailed in paragraph 3 1 1 4 2 1 Most Significant Character Sensor Reset Flag This will be set to on start up It will only be set to following receipt of an command If it subsequently is set to X this is an indication that a fault such as a power interrupt
102. racy Temperature and Humidity Sensor sese 85 Mains Adapter sack 85 iransit asesor rer o erp dh pte deir i Uh et tee rd rt bee ge 84 AFTER SALES SUPPORT te er ede eet e VI AMBIENT LIGHT SENSOR ipn dese desee o er RE e 3 25 26 38 85 B BACKSCATTER RECEIVER es 23 59 60 61 82 85 BAUD RATE rb t piede te D dei UR E 8 20 28 BIRAL SENSOR INTERFACE 1 8 28 55 58 61 65 4 Cable 4 CALIBRATION HN e epe Ut e 61 Calibration Certificate 254i ei RE ERI RE p IR titer eee t eee 8 Calibration Check eee HR ree eb ere e ee 61 ci PR 3 84 Calibrati n Kit Assembly 5 i ed ee bein ebd eee des 62 Precipitation teer i ERE CERCA Rede ee La HE 66 Re Cali bration son dta he RR a RO nn eei eee treten 64 eaaet can Des 66 CE CERTIFICATION SAFETY sites e
103. rear of the present weather sensor unscrew the small saddle which locates the system onto the mounting pole Place the appropriate end of the Precipitation Sensor mounting bracket under this saddle and replace This will locate the Precipitation Sensor immediately behind the back scatter head as shown in Figure 1 8 Precipitation Sensor Mounting Details Precipitation Sensor Mounting Bracket Grounding Screw Two Screws For Small Saddle Figure 1 8 Precipitation Sensor Mounting Details Mount the Precipitation Sensor to the mounting bracket as shown Mount the Present weather Sensor to the mast keeping the Present Weather Sensor orientation as shown in paragraph 1 5 3 Mount both the Temperature and Humidity Sensor and the optional Ambient Light Sensor to the mast as shown in Figure 1 7 VPF750 System Align the Ambient Light Sensor if fitted at a suitable angle above horizontal as defined by local requirements The Present Weather Sensor has between three to five connectors on its lower face A typical configuration is specified in paragraph 1 2 3 but the number and position of the connectors STEP 5 Installation 2 Biral Section 1 ATT Sensor Set up may vary depending on the exact configuration purchased The cables provided will only fit the appropriate connectors on the sensor 1 5 7 Electrical Grounding Possible instrument failure can result from the damaging effects of over voltage transien
104. rence plaque matches that on the label on the calibration arm If not do NOT use this assembly as it may not give a true calibration This assembly should then be attached to the sensor as shown in Figure 5 1 Assembly of Calibration Reference Plaque Note All commands should be terminated with Carriage Return gt and Line Feed crlf see Paragraph 1 3 The figure shows the calibration plaque assembly fixed to a VPF730 but the same configuration is used for the VPF710 and VPF750 Calibration Reference Plaque Calibration arm Figure 5 1 Assembly of Calibration Reference Plaque Example of calibration plaque in situ on VPF730 62 Calibration Check Section5 Biral Calibration Procedures Step 1 Clean all windows on the sensor using pure alcohol propanol and soft cloth or tissue preferably lens tissue Check the cleanliness using a portable light if possible Step 1 may not be necessary if checking or commissioning a new sensor Step 2 X Attach the calibration reference plaque to the sensor as shown in Figure 5 1 Assembly of Calibration Reference Plaque power to the sensor need not be removed Do not stand close to the sensor during calibration as reflections may cause errors in the reported values EXCO Zero Check Step 3 Insert GREY FOAM PLUGS the front of each window blocking out all light There are 3 foam plugs top left in the calibration case you will only use 2 of
105. rmance of the monitoring circuits can be checked by the following procedures Transmitter Window Monitor Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Clean the transmitter window Send the command R Verify that the Transmitter Window Contamination field value see paragraph 3 1 1 in the sensor response is 00 to 02 Insert a piece of white card or paper in the transmitter hood that blocks and almost touches the window Send the command R Verify that the Transmitter Window Contamination field value in the sensor response is much greater than 10 eg 99 Remove the white card Receiver Window Monitor s advanced self test configured sensors only This procedure is used for the forward scatter receivers on all sensors and the additional backscatter receiver on the VPF730 and VPF750 sensors Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Clean the forward scatter receiver window Wait for operational data in message from the sensor Send the command R Verify that the Forward Scatter Receiver Window Contamination field value see paragraph 3 1 1 in the sensor response is 00 to 02 Insert a piece of white card or paper in the forward scatter receiver hood so that it blocks the window and almost touches it Wait for operational data message from the sensor User Confidence Checks 59 Biral Maintenance Procedures
106. rn deett ap de eee OE ei rores dpt VII CHECK DATA MESSAGE eese ere epe tete tr rd epe ERES 9 CHECKSUM PEE 51 ERE 8485 681 14 15 16 17 Normal not RS485 4 AR AGP edere m e s 12 14 COMMANDS AND RESPONSES eher tnr e Reto ep mere uu Sue nents 31 52 Sensor Commalids dtr E REN RE ER ER SCENAM 48 Sensor RESPONSES aceite ee hors de ee ea ede e e Gus cabs be nk de E dea da 53 COMMUNICATIONS enne nennen 14 CONFIGURATION OPTIONS ier Depp o 10 100 Section 7 Product Overview 20 tede bbs RR ea al eis o I 12 E AEE E EAT ere 14 CONTACT DETAIES 9 E E EE AA DATA MESSAGES E SER E EE RE ERE ERIE EP REE 31 Variations for ALS WSM 38 MPETIO s e cd et nm perite det 32 Notas ri 34 5 39 DATE AND TIMB STAMP e ere RR 11 DIMENSI
107. s the EXCO value may NOT agree with that marked on your calibration reference plaque NB The sensor is fully calibrated before it leaves Biral STEP 3 Equipment Test 9 Sensor Set up section 1 1 4 10 STEP 4 Configuration Options There are a number of configuration options available for the user to select Three options are set using a configuration byte of the Options Word detailed in sections 1 4 1 to 1 4 6 The remainder are set using a configuration byte of the Operating State word These are set directly using commands starting with OS Each of these is detailed below in sections 1 4 7 to 1 4 10 1 4 1 Options Word The options word consists of two bytes Their current values can be determined by sending the OP command The reply will be as follows aaaaaaaa bbbbbbbb The upper byte aaaaaaaa is used to set internal operating parameters and should not be changed It will in general be 000000007 For the lower byte a value is entered as a binary number 1 s and 0 Leading 0 s in the value need not be entered The value is stored in non volatile memory and the operating configuration when power is applied is that set by the last entered options word The definition of each bit of this byte is shown below Table 1 6 Each bit ofthe lower byte of the Options Word is defined as follows bbbbbbbb Bit 1 1 Add Date and Time to the start of the data message 0 No Date and Time at
108. sage Meaning ALS ALS data message prefix ALS Signal minute averaged value cd m bbb ALS Self Test and Monitoring see paragraph 4 2 O Other self test values OK X Other self test fault exists O Window not contaminated X Window contaminated cleaning recommended required F Window contaminated fault S Sensor input saturated O Sensor not reset since last R command X Sensor reset since last R command Table 2 6 Message Extension for ALS 38 DATA Message Variations for WSM and ALS Section 2 Standard Operating Data 2 4 Data Output Message VPF750 2 4 1 The data message format is VPF750 Compressed Data Message lt Date gt lt Time gt CP nnn ww aa aa KM bb bbbb ccc c ddd eeeee fff lt cs gt lt crlf gt Message Meaning lt Date gt Optional Date string in the form DD MM YY lt Time gt Optional Time string in the form HH MM SS CP Compressed message header nnn Instrument identification number set by the user Present weather codes From WMO Table 4680 Automatic Weather Station ww NotReady first 5 minute from restart 00 No significant weather observed 04 Haze or Smoke or Dust 10 Mist 20 Fog in last hour but not at time of observation 21 Precipitation in last hour but not at time of observation 22 Drizzle in last hour but not at time of observation 23 Rain in last hour but not at time of observation 24 Snow in last hour but n
109. see previous section paragraph 5 1 power to the sensor need not be removed Send command CO Sensor replies OK Send command CE Sensor replies CLEAN WINDOWS BLOCK FWD SCAT RCVR OPTICS BLOCK TRANSMITTER OPTICS BLOCK BK SCAT RCVR OPTICS not for VPF710 INSTALL REF STD ENTER FWD SCAT EXCO FORM XXX XX Ensure that the windows are clean Fit the three foam plugs supplied with the calibration kit against the windows only 2 used for the VPF710 Enter Forward scatter EXCO value as written on the calibration plaque NOT VPF710 Sensor replies ENTER BACK SCAT EXCO KM FORM XXX XX Enter back scatter EXCO value as written on the calibration plaque Sensor Replies CAL IN PROGRESS Wait for approximately 2 minutes Sensor replies REMOVE OPTICS BLOCKS ENTER OK Remove foam plugs from all windows and send text OK Sensor replies CAL CONTINUES Wait for approximately 2 minutes Sensor replies CAL COMPLETE REMOVE REF STD Note Do not remove the calibration reference plaque at this point Sensor Re calibration 65 Biral Calibration Procedures Step 10 Step 11 Step 12 Step 13 Section 5 Wait for the third data message to be received at the PC Note the Total EXCO and the back scatter EXCO NOT VPF710 value s reported by the sensor If the Total EXCO reported is within 3 of the Forward EXCO value of the calibration plaque and Not fo
110. sent Weather message header aa Instrument identification number set by the user bbbb Last measurement period seconds cece Time since this report was generated seconds ddd dd KM Meteorological optical range km eee Precipitation type message NP No precipitation DZ Slight drizzle DZ Moderate drizzle DZ Heavy drizzle RA Slight rain RA Moderate rain RA Heavyrain SN Slight snow SN Moderate snow SN Heavy snow UP Indeterminate precipitation type GR Hail XX Initial value or error Obstruction to vision message ff blank obstruction HZ Haze FG Fog DU Dust FU Smoke Only if external temperature humidity sensor fitted BR Mist gg gg Receiver background illumination 36 Data Output Message VPF730 e Biral Section Standard Operating Data Message Meaning hh hhhh Amount of water in precipitation in last measurement period mm C Temperature C jjjj Number of precipitation particles detected in last measurement period kkk kk Transmissometer equivalent EXCO km EXCO less precipitation particle component km mmm mm Backscatter EXCO Two spaces delimiter nnnn Precipitation message index 000 Precipitation indicator 2 ppp Self Test and Monitoring see paragraph 4 2 O Other self test values OK X Other self test fault exists O Windows not contaminated X Windows contaminated
111. t Drizzle and Rain Moderate or Heavy Slight Rain Moderate Rain Heavy Rain Freezing Slight Rain Freezing Moderate Rain Freezing Heavy Rain Rain and Snow Slight Rain and Snow Moderate or Heavy Slight Snow Moderate Snow Heavy Snow Ice Pellets Slight Ice Pellets Moderate Ice Pellets Heavy Snow Grains Ice Crystals Rain Showers Slight Rain Showers Moderate Rain Showers Heavy Snow Showers Slight Snow Showers Moderate Snow Showers Heavy Hail Present Weather Measurements Section 7 Biral Section 7 7 4 Sensor Specifications Product Overview The specifications for all versions of the VPF700 series of sensors are summarised in the following pages To adapt the table to a particular sensor model disregard non pertinent information For example in the case of the Model VPF710 visibility sensor disregard those portions of the specification pertaining to precipitation measurements Atmospheric Extinction Coefficient EXCO and Precipitation Measurements Function Details Meteorological Optical Range MOR 10m to 75km Atmospheric Extinction Coefficient EXCO reductions in visibility caused by fog haze M smoke sand drizzle rain snow and general precipitation Measurement Accuracy at 16 km 10 Measurement Accuracy at 2 km 2 Measurement Time Constant 30 seconds Stability of EXCO Zero Setting Function Details Ambient T
112. tation Amount Calibration Biral Section gt gt Calibration Procedures The value to be entered to adjust the precipitation amount factor is calculated as follows Value entered _ Desired precipitation accumulation 100 Sensor s reported precipitation accumulation EXAMPLE Over several rainstorms a reference sensor measures an accumulation of 225 millimetres The sensor reported an accumulation of 244 millimetres To adjust the sensor s precipitation accumulation factor the value to be entered is 225 x 100 92 2 244 The suggested procedure to be used for precipitation amount calibration is as follows Step 1 Send the parameter command CO The sensor replies OK Step 2 Send the precipitation amount calibration command CA Sensor replies ENTER PRECIP AMT ADJ FACTOR IN PERCENT 30 0 TO 300 0 FORM XXX X Step 3 Send the required adjustment factor e g 92 2 Sensor replies CAL COMPLETE Step 4 The precipitation amount calibration process is complete Temperature Calibration Precipitation Amount Calibration 67 Biral Measurement Principles ___________ Section 6 6 MEASUREMENT PRINCIPLES 6 1 6 2 68 Visibility Measurement Terminology The VPF700 Sensor of Series has all the capabilities of a forward scatter meter FSM it belongs to the class of nephelometers which measure the amount of light scattered at angles less
113. the start of the data message Bit2 Notused Bit 3 0 Use temperature sensor value in PW determination This bit should not be changed Bit4 Not used Bit5 Not used Bit 6 1 Add a check sum character to all sensor output messages 0 Don t add check sum character to all sensor output messages Bit 7 1 Don t adjust EXCO and MOR values in data messages for measured window contamination 0 Adjust EXCO and MOR values in data messages for measured window contamination Bit8 1 Use RS485 addressable Communications protocol 0 Do not use RS485 addressable Communications protocol Table 1 6 Options Word lower byte STEP 4 Configuration Options 2 Section 1 Sensor Set up To set this word send command CO to enable changes and then command OPa0b0000c to set the Option Word as required For example send OP100000 to enable the checksum with no date and time stamp and not using RS485 leading 075 are not necessary in this command Bit 1 Date and Time enable Bit6 Check Sum enable and Bit 8 RS485 enable are the only bits which may be set to 1 by the user All other bits MUST be left at 0 for correct sensor operation The functions controlled by this byte are detailed in sections 1 4 2 to 1 4 6 The Default setting 00000000 1 4 2 Date and Time Stamp in data string By default the date and time stamp is not included at the start of the data string This 15
114. the type of precipitation Small numbers of particles with distributions not indicative of rain or snow are considered not to be precipitation and are rejected by false alarm algorithms Once precipitation occurrence has been determined the particle size distribution is used to measure the intensity To measure the intensity the number of particles in each size bin of the matrix are summed and then multiplied by the equivalent volume of water and a calibration constant If the precipitation is identified as snow a density factor is applied to determine the equivalent water content Because the size velocity matrix is a convenient presentation for identifying various forms of precipitation we have termed it the Precipitation Recognition Matrix Types of precipitation are identified from their Signature in the Precipitation Recognition Matrix The Signature is the particle size velocity distribution that is characteristic of each type of precipitation phenomena An example of a precipitation recognition matrix is shown in Figure 6 3 Precipitation Matrix This figure portrays a 16 x 21 matrix array of particle sizes and velocities Sizes are arranged in columns and velocities in rows Precipitation Measurements T Biral Measurement Principles Section 6 The Marshall Palmer model for raindrop s
115. these for the VPF710 Step 4 Send the command RST Verify the response Step 5 Ifthe sensor is operating in the polled mode send the D command at 60 seconds intervals If the sensor is set to automatically output data then the sensor will output data every 60 seconds Step 6 Wait for the fifth 5 data message from the sensor Send the command Check that the response 1s between 0 00 and 0 05 Step 7 NOT for VPF710 Send the command Verify that the response is between 0 10 and 0 10 Step 8 Remove the foam plugs EXCO gain Check Step 9 Send the command RST to restart the sensor Verify the response is Step 10 Ifthe sensor is operating in the polled mode send D command at 60 seconds intervals If the sensor is set to automatically output data then the sensor will output data every 60 seconds Step 11 Wait for the fifth 5 data message from the sensor Send the command Check that the response is within 5 of the Forward EXCO value assigned to the calibration reference plaque the value on the label attached to the plaque Step 12 NOT for VPF710 Send the command BB Check that the response is within 10 of the Back EXCO value assigned to the calibration reference plaque the value on the label attached to the plaque Calibration Check 63 Calibration Procedures S Section 5 Step 13 Remove the calibration ref
116. this configuration are provided in paragraph 1 4 8 pagel8 Note All responses from the sensor are appended with carriage return and line feed characters crlf see Paragraph 1 3 The following paragraphs provide full details of the compressed and the expanded data messages for each sensor in the series 2 Standard Operating Data 31 Biral Standard Operating Data Section 2 2 1 Data Output Message VPF710 21 1 VPF710 Compressed Data Message The data message format is lt Date gt lt Time gt C Paa bbb bb cec lt cs gt lt cerlf gt Message Meaning lt Date gt Optional Date string in the form DD MM YY lt Time gt Optional Time string in the form HH MM SS CP Compressed message header aa Instrument identification number set by the user bbb bb Total EXCO in km ccc Self Test and Monitoring see paragraph 4 2 O Other self test values X Other self test fault exists Windows not contaminated X Windows contaminated cleaning recommended required Windows contaminated fault Sensor not reset since last command X Sensor reset since last R command lt cs gt If selected this will be the checksum character The checksum is off by default Table 2 1 VPF710 Compressed Data Massage Two typical compressed data messages from a VPF710 are as follows CP01 000 10 000 CP01 000 12 000 32 Data Output Message VPF710 2
117. tions in fog and haze are as follows 0 55 roc 0 88 0 13 0 55 2 0 88 0 22 Thus a FSM operating at 0 88 micron and calibrated fog will show a phase function difference in haze by the amount 0 88 0 88 1 7 0 88 For a FSM operating at 0 88 microns two wavelength dependent components of the angular scattering coefficient are in the opposite direction and nearly offset one another The net result is that a calibration made in fog will be applicable to haze situations Such is not the case for a FSM operating at 0 55 microns At that wavelength there is no spectral difference between FSM and a visible light transmissometer The total scattering coefficient portion of the angular scattering function will remain unchanged but the phase function will jump in the transition from fog to haze Larger than true extinction coefficients will result with the subsequent underestimation of the true visual range in haze Precipitation Measurements An automated present weather sensor must be capable of determining the type intensity and quantity of precipitation in addition to the visibility In the case of the VPF700 series of sensors these precipitation parameters are established by a combination of several methods Precipitation Measurements Biral 6 AM Measurement Principles 6 5 1 Identification
118. toring see paragraph 4 2 Other self test values OK X Other self test fault exists F Forward Scatter Receiver Flooded with Light B Back Scatter Receiver Flooded with Light T Temperature Humidity sensor Fault O Windows not contaminated X Windows contaminated cleaning recommended required F Windows contaminated fault O Sensor not reset since last R command X Sensor reset since last R command 00 0000 Amount of water in precipitation in last minute mm ppp ALS Self Test and Monitoring see paragraph 4 2 O Other self test values OK X Other self test fault exists O Window not contaminated X Window contaminated cleaning recommended required F Window contaminated fault S Sensor input saturated O ALS not reset since last R command X ALS reset since last R command 4444 One minute particle count lt cs gt If selected this will be the checksum character The checksum is off by default 44 Table 2 8 VPF750 Expanded Data Message Data Output Message VPF750 Section 2 Standard Operating Data Two typical expanded data messages from a VPF750 are as follows VPF750 001 0060 09 30 KM 52 DZ 000 426 08 76 KM 000 32 000 14 008 6 086 099 00125 000 00 0071 000 0148 000 612 08 35 000 30 750 001 0060 09 87 62 5 000 12 008 6 C 086 5 099 0013
119. ts induced on the power line and the signal distribution lines Destruction of sensitive components can result from unprotected lines or instrument failure may occur over a long period of time due to slow device degradation Destructive over volt transients can occur in many ways e g lightning induced transients AC power line transients and EMI RFI electromagnetic noise The power control subsystem of the sensor contains transient surge arrestors on all power and signal lines as a standard feature EMI filters are present on the power and lines entering the power control subsystem It is essential to connect the sensor to earth ground for maximum protection of the instrument The following notes are intended to provide some guidance in the design and construction of an electrical grounding system 1 Ground Rod An eight foot ground rod should be used to make contact with moist soil during even the driest periods 2 Lead Lengths No 6 AWG solid copper wire should be used to connect the instrument and thus the transient voltage suppressers to the ground rod Use the shortest and most direct paths to the ground Simply connect the ground lead to the grounding screw provided on the front of the lower mounting flange of the instrument Figure 1 8 Precipitation Sensor Mounting Details 3 System Interconnections Eliminate all isolated ground loops The shield of the signal output cable for example should be attached only at
120. wn for model VPF710 with compressed data message The temperature sensor has a long thermal lag The temperature reading can be incorrect for at least 30 minutes if the sensor is moved from one location to another of different temperature just prior to testing In operation at a fixed site this is not a problem because ambient temperature changes are slow If a very accurate check of the temperature reading 15 required the sensor should be operated for at least 60 minutes at a fairly constant temperature before making the check A verification of correct operation of the temperature sensor can be made without this warm up period The check is made as follows Step 1 Use as a reference standard a thermometer accurate to 1 degree C Ensure the standard thermometer has had time to stabilise to the ambient temperature environment Step 2 Verify that the value in the temperature field in the sensor data message matches the reference thermometer reading to within 3 C 5 for VPF710 4 3 3 Window Monitor Checks The VPF700 series of sensors monitor the transmitter window and if the option has been specified at time of order the forward and back scatter receiver windows The values measured 58 User Confidence _ B ira Section 4 Maintenance Procedures are used to adjust the EXCO value and are also used to determine when the windows should be cleaned The perfo

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