Model 6497 Present Weather and Visibility Sensor User`s Manual
Contents
1. the 4 bytes of CRC Table 1 AWOS Output Data Format AWOS Output Data Format Segment Length bytes Description Example Extinction coefficient 3 extinction coefficient 1 16 blank Status Word 0 4 Not used 0048 h blank Status Word 1 4 Not used 0000 h blank Status Word 2 4 Not used 0004 h blank ALS value up to 5 digits ALS data 245 blank padetcomer re blank 8365 flag 1 1 if 8365 0 if another visibility sensor model 1 blank ending sequence 3 always 0 lt sp gt 0 lt sp gt 0 000 CRC 2 CRC MSB ASCII byte XX CRC 2 CRC LSB ASCII byte XX Termination 1 2 CR LF x h signifies that the number shown is a hexadecimal number 25 Model 6497 Present Weather and Visibility Sensor User s Manual 6 MAINTENANCE AND TROUBLESHOOTING Equipment Required e Clean Cotton Cloth or Lens Tissue e Common Household Glass Cleaner 6 1 MONTHLY MAINTENANCE 1 Check Lens Heaters With a clean finger touch the lenses in front of the disc shaped heaters which are bonded to the upper and lower inside surface of lenses The lens surfaces should be slightly warmer to the touch than the ambient temperature 2 Clean Lenses Cleaning the lenses should be done with lint free cloth and cleaning solution Clean the lenses by first spraying the lens cleaner on the lens and then wipe gently to prevent scratching the glass optics In actual practice moderate dust buildup2. e Online support is available by filling out a request at www allweatherinc com customer support html e E mail your support request to support allweatherinc com Model 6497 Present Weather and Visibility Sensor Revision A Date 2012 J un 30 Initial release Revision History Summary of Changes User s Manual Model 6497 Present Weather and Visibility Sensor User s Manual TABLE OF CONTENTS Ve VE RMI sedi cots vac a OA odias 1 GPS URE S771 10 a eee a e RI PORE TANT O NA EAE OR OER AERIS 1 T2 Nidia AN A ELSA ANS asd Se SO Reha 2 PA O oat Mamieciisecets oe 2 A O AO LEN DESSRIPTION ta tac n 3 2 Maor Components ara Ea E E E ee BS alee enn Re R 3 Zlat Sensor A O 3 2 152 Electromes Enclo UT iii lala las 4 213 AC Titerface Board id 4 3 THEORY OF OPERATION aaa aia 5 3 Sensor A ai uk Sid sa Buc Dae ie en DA A Sas Bag NN 5 3 2 Digital Signal Processing DSP Al gorithm cceececcceesseceseceseceeeeeeseecsaeceseeneeeeeaeecaeeneeeeees 6 3 2 DSP Algorithm MOdules AA aseaaatucssatey a a Aa RST 6 A INSTALLATION A 8 4 1 Siting and Installation Guidelines 0 ccccecccesecsseeseesseeeeceecesecseecseesseeeeesaeceaecsaecaeenseeeeeseeeesees 8 4 2 Mechanical Installation sica 10 42k A 10 4 2 2 Mountithe Sensor Heads ernia das dect devise 11 4 2 3 Install the Electronics EncloSUTE ccconoonoocnnnnoncconanonanannnonncnononnnnonononconononnnn no nnncnccnonnnns 13
3. TOWER LEG REF A 2X 40 UNISTRUT SS M009032 00 as 8X WASHER FLAT 1 4 20 58 40 UNISTRUT SS 1144 20 REF 4X 1 UNISTRUT CLAMP SS M009041 00 M408149 01 umm H i w TOWER LEG HARDWAREIINCLUDEDWITH 8X NUT UNISTRUT 1 4 20 8S REF CLAMP M408149 01 M408506 00 B 40 UNISTRUT SS ENCLOSURE REF B B ENCLOSURE A ABBY REP SECTION D ASSEMBLY REF section A A Figure 8 Mounting Hardware Details Figure 8 shows the details of securing the mounting hardware These additional steps will help keep the mounting secure and corrosion resistant e Apply anti seize compound to all external threaded connections e Once the installation of the enclosure has been completed apply a light spray of corrosion block to all metallic connectors and threaded fasteners 14 Model 6497 Present Weather and Visibility Sensor User s Manual 4 3 ELECTRICAL CONNECTIONS Figure 9 shows the external connections at the bottom of the enclosure e AC power conduit e Battery backup cable optional e Signal cable from sensor head e Signal cable to Data Collection Platform DCP A user supplied ground wire should also be connected to the ground lug to ground the Model Model 6497 Present Weather and Visibility Sensor to earth potential per local electrical codes AC POWER CONDUIT FROM SERIAL CABLE SENSOR HEAD TO DCP Figure 9 External Connections at Enclosure Bottom Route the cable from the sensor head to the bottom of the electronics enclos
4. 4 3 Electrical COMES AAA AAA A did 15 4 3 1 RS 485 Connections to the AWOS Data Collection Platform occononnoononnnonccnnnnnn 18 4 3 2 Connecting the Sensor to the AC Power Line coooococnnocccnoncccnoncnononcnononccnonnccnonnc cono ncnnnnos 18 5 OPERATION WITH AN AWOS DATA COLLECTION PLATFORM 20cccceeeeeeeeeees 19 SN Sensor Reports AS II AE TO ATA a a E AA 19 51 10 Present Weather Polls cian aida ii 19 5 1 2 Present Weather Data Interpreta Oi acnecaseqaayasevcsdceceseeucienceaiseteqnasaasacessanseee 20 51 3 Visibilty Pol cos 25 6 MAINTENANCE AND TROUBLESHOOTING occocccccnncncnnnccnnncccnonacononanoconacononacanonacinonaninns 26 6 1 Monthly Maintenance ii 26 6 2 Tiann al Maintenance AAA A A A 27 Lo PECIFICGA TON Soros 28 8 WARRANTY ecards 30 Model 6497 Present Weather and Visibility Sensor User s Manual 1 OVERVIEW The Model 6497 Present Weather and Visibility Sensor is the most advanced sensor of its kind ever made The fully automated instrument provides accurate visibility present weather and precipitation measurement capabilities in a single sensor This next generation intelligent sensor uses all digital signal processing for no drift high accuracy results The Model 6497 Present Weather and Visibility Sensor measures visibility and detects and quantifies rain snow drizzle freezing and mixed precipitation conditions The sensor is designed for year round continuous operation in all clim
5. 1 SENSOR HEAD The sensor head is a self contained unit consisting of electro optical components heaters a digital signal processor and integral cabling to connect with the electronics enclosure The sensor measures precipitation by detecting the optical irregularities induced by particles falling through a beam of partially coherent infrared light in the sample volume These irregularities are known as scintillation The twinkling of stars is a familiar example of scintillation The precipitation rate is determined by detecting the intensity of the scintillations that are characteristic of precipitation The precipitation type rain snow etc is determined by analyzing the frequency spectrum of the induced scintillation Precipitation is measured using the sensor head in beam optics The sensor measures visibility by determining the amount of forward scattered light received at the off axis detector Light is scattered by precipitation dust smoke fog and other obstructions to visibility in the sample volume This signal known as the scatter coefficient is converted to visibility using a proprietary algorithm Visibility is measured using the sensor head off axis optics A precision thermistor type temperature probe is attached to the bottom of the receiver box It is used for automatic temperature compensation in the algorithm The temperature measured by the probe is not meant for meteorological reporting purposes T
6. The full aperture is used on the off axis optics Sea po POOTO fx Ae SAMPLE VOLUME aa sais DIODE A a o o PREAMP o o a O OFF AXIS PREAMP RX LENS TO VIS MODULE FROM TX MODULE TO AGC MODULE Figure 2 Sensor Operation Block Diagram Signals from the sensor head are carried in a cable to the electronics enclosure 3 2 DIGITAL SIGNAL PROCESSING DSP ALGORITHM The electronics supporting the 6497 are integrated inside the sensor head This section describes the modules that make up the functionality for the DSP algorithm The Present Weather Sensor digital signal processor contains several components for power distribution analog signal processing and digital processing 3 2 1 DSP Algorithm Modules AGC Module Automatically adjusts the signal level received from the sensor front end and demodulates the precipitation induced modulation signal from the carrier frequency SP1 Channel Contains two elements the carrier X channel and the low L channel The carrier channel is used to diagnose the carrier signal strength The low channel detects precipitation induced frequencies in the range of 25 to 250 Hz that are associated with snow SP2 Channel Contains two elements the particle counting K channel and the high H channel The particle channel detects the occurrence of falling precipitation The high channel detects precipitation induced frequencies in the range of 1 to 4 kHz that are
7. and scratches on the lenses will not have any discernible effect on the instrument 26 Model 6497 Present Weather and Visibility Sensor User s Manual 6 2 TRIANNUAL MAINTENANCE Check the strength of the carrier signal by displaying the present weather status display on the DCP s LCD display screen Press the or keys until the screen is displayed The data fields in bold shown below are the channels of interest W__ P0000S0000VvvvvccXnnnzzzLInnnbbbKnnnbbbHnnnbbbEnnngggTttt 1 Quick Check on Data Fields The following checks are general in nature and should be used as a general indication that the sensor is working properly This test should be performed when there is no precipitation and after the sensor has stabilized for at least 30 minutes Display the present weather data screen on the DCP s LCD display screen using the and keys Present Weather Data W__P0000S0000 W The present weather field should not contain any data two underscores if there is no precipitation falling S0000 The status fields should all read zero if the 6497 has been operating and not reset by a power interruption for at least 5 minutes If the status fields are not all zeros refer to Section 5 4 2 for an interpretation of the possible problem Hint If the Quick Check values do not appear to be correct record at least 10 minutes of the complete status string and fax them to the All Weather Inc Customer Service department 916 9
8. in Figure 8 Feed the power cable through the conduit fitting A 3 wire 16 to 18 AWG cable is recommended Crimp fork type terminals to the ends of the wires Connect the three power cable wires to the AC Interface Board terminal blockTB1 pins 1 LINE 2 NEUTRAL and 3 GND Model 6497 Present Weather and Visibility Sensor User s Manual 5 OPERATION WITH AN AWOS DATA COLLECTION PLATFORM 5 1 SENSOR REPORTS The Model 6497 Present Weather and Visibility Sensor is a polled sensor and the sensor responds when the sensor is polled by the Data Collection Platform Either a present weather or a visibility poll command will be sent The serial interface consists of a three wire RS 485 connection 5 1 1 Present Weather Polls Data transfer across the serial interface is implemented via a serial ASCII encoded half duplex 4800 bps asynchronous transfer link Data transfer in the DCP to sensor direction is limited to a eight character poll PRWX00 lt CR gt lt LF gt Data transfers in the sensor to DCP direction are fixed format ASCII strings starting with an equals sign and terminated with a carriage return and line feed lt CR gt lt LF gt The carrier return and line feed allow the use of printers or terminals in monitoring the data The sensor is polled once a second and the current wind information is updated The present weather information is formulated into the poll response once a poll command is received The param
9. the sensor head and the mounting bracket with the 4 20 hex locking nuts as shown in Figure 2 To mount the head to a vertical mast or tower section install the U bolts and mounting bracket horizontally To mount to a horizontal tower section or boom arm install them vertically using the same holes Note that the metallurgy of the stainless U bolts will cause the nuts to seize to the U bolts and twist them off Lubricate the threads with anti seize compound before assembling Do not tighten the nuts completely until the sensor head is installed on the mast or tower and is oriented on the north south axis as shown in Figure 3 11 Model 6497 Present Weather and Visibility Sensor User s Manual 2 Rotate the sensor head until the receive lens is facing north NN i L Figure 4 Sensor Head Orientation When mounting the sensor head on a tower choose the tower leg that gives the larger head an unobstructed view to the North without rotating the head assembly into the tower The head assembly should be completely outside the tower as much as possible 3 Tighten the U bolt nuts when the orientation is correct Do not overtighten such that the mounting plate is bent 4 Route the cables along the mast or tower to the electronics enclosure and secure them to the mast or tower every meter using tie wraps or other straps 5 Connect the ground cable to a ground rod TIE WRAP AS NEEDED paa MOUNTING Po POLE GREEN GR
10. the warranty Model 6497 Present Weather and Visibility Sensor User s Manual 2 1 2 Electronics Enclosure The electronics enclosure contains the processing electronics power supplies and surge protection circuits The electronics enclosure is a fiberglass NEMA 4X type box with a hinged access door One power supply and AC and RS 485 interface modules with surge protection are mounted to the base plate of the enclosure Figure 9 shows the locations of these components inside the enclosure All of the units in the enclosure are field replaceable The electronics enclosure is mounted with the supplied fastener hardware using the four 4 mounting holes on the enclosure If a 6497 is purchased by itself there no mounting hardware is provided Note Exercise care to avoid drilling or otherwise puncturing the electronics enclosure 2 1 3 AC Interface Board Two fuses are located on the AC Interface Board see Figure 1 Though installed fuse F2 is only used for the 6497 Replace the fuses only with fuses of the same rating as shown below Fl 10 A 250 V 5x20 mm slow blow F2 5 A 250 V 5x20 mm slow blow not used 2 115 230 V F2_5A SELECTION 230 V F1 10 A MAIN ON OFF SWITCH Figure 1 AC Interface Board Note that there is a plastic safety shield over the AC Interface Board The fuse holders protrude through the cover Model 6497 Present Weather and Visibility Sensor User s Manual 3 THEORY OF OPERATION 3
11. 0 m 3 Sensor Height Rigidity Verticality and Orientation The OFCM recommends that the Present Weather Sensor be mounted at a height of 10 ft 3 m This height is not always possible because of constraints imposed by the site Mounting the sensor head lower than 2 m or higher than 5 m is not generally recommended For AWOS installations All Weather Inc recommends that the sensor head be mounted on a pipe If the pipe mast is more than 5 cm 2 in diameter a mast coupling with a diameter of 5 cm 2 or less should be placed on top of the pipe The 6497 may also be installed on the sensor tower at a height of 10 ft above the tower base Install the controller box on the tower close to the AWOS Data Collection Processor box When installing on the Model 8518 A Foldover Tower mount the Present Weather Sensor to the hinged side of the tower The installation must be rigid so that wind induced vibration does not cause false alarms This can be accomplished by mounting the sensor to a thick wall pipe such as Schedule 40 type or to a rigid boom arm 1 m in length or shorter The Present Weather Sensor may be mounted on the top of a building is acceptable if it located near the center of the building away from the wind turbulence that may occur near the edges Model 6497 Present Weather and Visibility Sensor User s Manual The sensor head must be mounted vertical within 2 degrees so that the line aperture on the in beam lens is hori
12. 0x5280 0x9241 1 0x5500 0x95c1 0x9481 0x5440 1 0x5f00 0x9fc1 0x9e81 0x5e40 0 0x9901 0x59c0 0x5880 0x9841 1 0x4b00 0x8bc1 0x8a81 0x4a40 0 0x8d01 0x4dc0 0x4c80 0x8c41 0 0x8701 0x47c0 0x4680 0x8641 0x8201 0x42c0 0x4380 0x8341 0x4100 0x81c1 0x8081 0x4040 cre ival while length cre cre_vals stringt crc amp Oxff return crc end crcl6 routine 24 A cra gt gt 8 amp Oxff Model 6497 Present Weather and Visibility Sensor User s Manual 5 1 3 Visibility Polls Data transfer across the serial interface is implemented via a serial ASCII encoded half duplex 4800 bps asynchronous transfer link Data transfer in the DCP to sensor direction is limited to a eight character poll VISIOO lt CR gt lt LF gt Data transfers in the sensor to DCP direction are fixed format ASCII strings starting with an equals sign and terminated with a carriage return and line feed lt CR gt lt LF gt The carrier return and line feed allow the use of printers or terminals in monitoring the data The sensor is polled once a second and the visibility information is updated e Poll Command VISIO0 lt CR gt lt LF gt CR a carrier return character 0xD LF a line feed character OXA e Poll Response The AWOS format data packet consists of the extinction coefficient as calculated by the 6497 and other data The cyclic redundancy code CRC16 covers all bytes up to but not including
13. 1a40 0x1e00 0xdec1 0xdf81 0x1f40 0xdd01 0x1dc0 0x1c80 0xdc41 0x1400 0xd4c1 0xd581 0x1540 0xd701 0x17c0 0x1680 0xd641 0xd201 0x12c0 0x1380 0xd341 0x1100 0xd1c1 0xd081 0x1040 0xf001 0x30c0 0x3180 0xf141 0x3300 0xf3c1 0xf281 0x3240 0x3600 0xf6c1 0xf781 0x3740 0xf501 0x35Cc0 0x3480 0xf441 0x3c00 0xfcc1 0xfd81 0x3d40 0xff01 0x3fc0 0x3e80 0xfe41l Oxfa01 0x3ac0 0x3b80 0xfb41 0x3900 0xf9c1 0xf881 0x3840 0x2800 0xe8c1 0xe981 0x2940 0xeb01 0x2bc0 0x2a80 0xea41 Oxee01 0x2ec0 0x2f80 0xef41 0x2d00 0xedc1 0xec81 0x2c40 0xe401 0x24c0 0x2580 0xe541 0x2700 0xe7c1 0xe681 0x2640 0x2200 0xe2c1 0xe381 0x2340 0xe101 0x21c0 0x2080 0xe041 0xa001 0x60c0 0x6180 0xa141 0x6300 0xa3c1 0xa281 0x6240 0x6600 0xa6c1 0xa781 0x6740 0xa501 0x65c0 0x6480 0xa441 0x6c00 Oxaccl 0xad81 0x6d40 0xaf01 0x6fc0 0x6e80 0xae4l 0Oxaa01 0x6ac0 0x6b80 0xab41 0x6900 0xa9c1 0xa881 0x6840 0x7800 0xb8c1 0xb981 0x7940 0xbb01 0x7bc0 0x7a80 0xba41 Oxbe01 0x7ec0 0x7f80 0xbf41 0x7d00 0xbdc1 0xbc81 0x7c40 0xb401 0x74c0 0x7580 0xb541 0x7700 0xb7c1 0xb681 0x7640 0x7200 0xb2c1 0xb381 0x7340 0xb101 0x71c0 0x7080 0xb041 23 Model 6497 Present Weather and Visibility Se 0x5000 0x90c1 0x5a00 0x9acl 0x4e00 0x8ec1 nsor 1 0x9181 0x514 0x9601 0x56c0 0x5780 0x974 0x9c01 0x5cc0 0x5d80 0x9d4 0x9b81 0x5b4 0x8801 0x48c0 0x4980 0x894 0x8f81 0x4f4 0x4400 0x84c1 1 0x8581 0x454 User s Manual 0 0x9301 0x53c0
14. 2 2 R 3 3 3 3 E 4 4 4 4 S 5 5 5 5 E 6 6 6 6 R 7 7 7 7 vV 8 8 8 RESET 8 E 9 9 9 9 D A status code of 0 in bytes 11 12 13 or 14 indicates no problem while a number or letter other than 0 indicates one or more FRUs may be defective For instance if byte 11 read 1 then FRU 2 should be checked Example Status codes read S0180 Interpret this code as follows Byte 11 0 OK Byte 12 1 FRU 1 probably bad Byte 13 8 Sensor was reset in past 5 minutes Byte 14 0 OK Solution Wait for 5 minutes to verify that the reset bit turns off The status code will now read S0100 indicating that there may be a problem with FRU 1 Replace FRU 1 Sensor Head and recheck the status code After 5 minutes when reset bit turns off again status codes should be S0000 Model 6497 Present Weather and Visibility Sensor User s Manual In normal operation excluding the first five minutes after reset or power up the status bytes will be all low 0000 A non zero character in any of the four positions indicates the suspected failure of an FRU The host system should take action to alert maintenance personnel of a possible problem In addition data from the OWI should be disregarded and a missing report issued Note that the sensor does not necessarily stop outputting data when a status bit flags an error condition The table below summarizes the active status bits and the corresponding FRUs and assembly numbers Item Description All Weath
15. 28 1165 for evaluation Include the weather conditions at the site during the period in question air temperature wind speed type of precipitation if any etc 27 Model 6497 Present Weather and Visibility Sensor 7 SPECIFICATIONS User s Manual Parameter Specification Present Weather Codes Reported gt 50 NWS and WMO codes Rain Dynamic Range 0 1 3000 mm h Rain Accumulation 0 1 999 999 mm Rain Accumulation Resolution 0 001 mm Rain Accumulation Accuracy 5 Snow Dynamic Range 0 01 300 mm h water equivalent Snow Accumulation 0 001 999 999 mm water equivalent Visibility Accuracy Snow Accumulation Resolution 0 001 mm Snow Accumulation Accuracy 10 Visibility Dynamic Range 0 001 10 km 10 up to 5 km 15 up to 10 km Visibility Time Constant 3 min harmonic Visibility Contrast Threshold 5 Ambient Light Dynamic Range Serial Data Data Update Rate 0 107 000 Im m Once per minute Serial Output RS 485 Output Format ASCII characters Baud Rate 4800 bps Serial Port Parameter Setting Power Requirements Supply Voltage 8 N 1 8 data bits no parity 1 stop bit 115 230 V AC 50 60 Hz 50 VA Transient Protection Environmental AC power and RS 485 signal lines fully protected S o Operating Temperature eee z O Storage Temperature ees Relative Humidity 0 100 nonconden
16. Model 6497 Present Weather and Visibility Sensor Users Manual Rev A allweatherinc All Weather Inc 1165 National Drive Sacramento CA 95834 USA 800 824 5873 www allweatherinc com Copyright 2012 All Weather Inc All Rights Reserved The information contained herein is proprietary and is provided solely for the purpose of allowing customers to operate and or service All Weather Inc manufactured equipment and is not to be released reproduced or used for any other purpose without written permission of All Weather Inc Throughout this manual trademarked names might be used Rather than put a trademark symbol in every occurrence of a trademarked name we state herein that we are using the names only in an editorial fashion and to the benefit of the trademark owner and with no intention of infringement All Weather Inc and the All Weather Inc logo are trademarks of All Weather Inc Disclaimer The information and specifications described in this manual are subject to change without notice Latest Manual Version For the latest version of this manual see the Product Manuals page under Reference on our web site at www allweatherinc com O aliweatherinc All Weather Inc 1165 National Drive Sacramento CA 95834 Tel 916 928 1000 Fax 916 928 1165 Contact Customer Service e Phone support is available from 8 00am 4 30pm PT Monday through Friday Call 916 928 1000 and ask for Service
17. OUND CABLE GROUND ROD CONCRETE FOOTER USER SUPPLIED Figure 5 Installation of Ground Cable 12 Model 6497 Present Weather and Visibility Sensor User s Manual 4 2 3 Install the Electronics Enclosure Two mounting kit options are available to mount the electronics enclosure e Standalone Mounting Kit AWI part number M488173 01 e Tandem Mounting Kit to mount Present Weather Sensor on same mast tower location as the Data Collection Platform AWI part number M488176 01 Attach the electronics enclosure to the Unistrut brackets using the hardware supplied with the sensor Figure 6 and Figure 7 show the mounting arrangements for the two mounting options _ 7 2X MOUNTING RAIL 14 M105078 01 _ 4X 250 WASHER FLAT M008041 00 17 4X 250 WASHER LOCK M008032 00 774X SCREW 7 250 20 X 1 00 MO12004 00 e SL 2x PIPE CLAMP FOR 2 1 2 PIPE 408473 MasT OZ ge A ANS A Y Figure 6 Standalone Enclosure Mounting 13 Model 6497 Present Weather and Visibility Sensor User s Manual p eS Q 4 Y NY 6497 PRESENT 1190 WEATHER DCP AND VISIBILITY SENSOR a 4a reso H W W Dobe coH E UO E oss o WSR RA v AAAS PASSA II RAR AST BX SCR 1 4 20 X 1 55 M012004 00 8X WASHER LOCK 1 4 20 58
18. V 230 V AC 1 3 ACCESSORIES The following accessories and replacement parts are available for the Model 6497 Present Weather and Visibility Sensor Part Number Description M488173 01 Standalone Mounting Kit Tandem Mounting Kit M488176 01 to mount Present Weather Sensor on same mast as Model 1190 Data Collection Platform M404806 Serial Sensor Interface Board 442071 aa V 5x20 mm slow blow fuse F1 AC Interface 5 A 250 V 5x20 mm slow blow fuse F2 AC Interface M442070 Board not used Model 6497 Present Weather and Visibility Sensor User s Manual 2 SYSTEM DESCRIPTION 2 1 MAJOR COMPONENTS 2 1 1 Sensor Head The sensor head uses a uses a compact triple aperture optical system to measure both precipitation and visibility The sensor head frame is an all aluminum welded design The small box TX is the transmitter unit and contains an infrared diode and lens with dual heaters The large box RX contains two independent receiver sections each consisting of a photo diode a lens with dual heaters and preamplifier electronics These two sections operate independently The first receiver detects present weather in beam and the second receiver detects visibility off axis A small panel is attached to the sensor arm to block stray transmitter light from entering the off axis receiver The generated signals are sent to a Digital Signal Processor board located behind the receivers Th
19. associated with rain Model 6497 Present Weather and Visibility Sensor User s Manual VIS Module Contains the amplification filtering and synchronous detection to extract the forward scattered signal related to the visibility TX Module Contains the voltage controlled oscillator and amplifier to drive the LED in the sensor head Digital Module Contains the A D sample and hold and digital control logic to sample the outputs of the signal processing cards It determines the precipitation type and intensity using algorithms The digital module also performs real time self tests to continually detect faults in the sensor and contains the serial communications port Flash ROM Module Contains an onboard programmable flash ROM and control circuit A new program can be remotely downloaded without any hardware change Ancillary Subassemblies There is one DC to DC converter that provides regulated 5 12 and 12 V DC to the analog and digital electronics The unregulated input voltage nominally 12 V DC is supplied to the lens heaters in the sensor head The 12 V DC input and serial signal line are fully protected from lightning surges by separate modules Model 6497 Present Weather and Visibility Sensor User s Manual 4 INSTALLATION 4 1 SITING AND INSTALLATION GUIDELINES The Model 6497 Present Weather and Visibility Sensor may be installed almost anywhere outdoors An area free and clear of obstructions and contamination so
20. ate types ranging from extreme arctic to deserts and tropical rain forests A major advantage of the Model 6497 Present Weather and Visibility Sensor is that the measurements are not affected by the buildup of dust dirt or ice on the lenses The weather processing software includes an artificial intelligence and fuss logic based algorithm that makes the baselines self adaptive This corrects the scintillation and forward scattering coefficient changes caused by the gradual obscuration of the light path The need for frequent lens cleaning is eliminated enabling the Model 6497 Present Weather and Visibility Sensor to operate for long periods of time completely unattended 1 1 FEATURES e Combines present weather identification precipitation measurement and visibility into a single rugged package e Outstanding performance yet low cost e No field calibration required e Used advanced scintillation technology e Intelligent algorithms based on over 100 million hours of sensor field data e Rugged design field proven from tropical to arctic environments e Easy installation and integration e Long term reliability designed for unattended operation year round e Unaffected by dust or buildup on lenses e Reports over 50 NWS WMO codes e Virtually no maintenance required e Built in self diagnostics and testing Model 6497 Present Weather and Visibility Sensor User s Manual 1 2 MODELS One 6497 model is available Model Description 6497 115
21. e dual lens heaters prevent dew frost and snow from building up on the lenses and are self regulating devices They are on continuously drawing more current when the outside temperature is cold and less current when the temperature is warm All wiring between the transmit and the receive heads is within the welded head frame The sensor head is completely sealed from water intrusion at the factory Exercise care should to avoid drilling or otherwise puncturing the frame The connecting cable for power and data is found at the bottom of the receiver box along with the temperature probe The 7 6 m 25 ft cable is supplied as part of the sensor to connect the Model 6497 Present Weather and Visibility Sensor to the electronics inside the electronics enclosure A 20 threaded hard point and screw are provided on the side of the receiver for electrical grounding A green ground cable is included to connect the sensor to earth ground The terms ground electrical ground and earth ground are defined by the National Electric Code or governing local authority A mounting plate an integral part of the sensor head cross arm is provided to install the head to a user supplied mast Two sets of holes in the mounting plate allow the U bolts supplied with the head to clamp the head to either a vertical or horizontal pipe up to 50 mm in diameter Note The sensor head frame contains no user serviceable parts opening the head will void
22. er Inc P N Sensor Head Assembly M482228 00 Electronics Power Supply M403510 00 The FRUs are available for maintenance and repair of the sensor in the field or depot The sensor head contains no user replaceable parts and can not be repaired except at the factory 22 Model 6497 Present Weather and Visibility Sensor User s Manual Check Sum Calculation The CRC is calculated using a standard cre 16 formula The algorithm is as follows CRC routine used with AWOS remote sensors USE cre crcl6 buffer length initial_value where cre is the returned value buffer is the data buffer to compute a crc length is the number of bytes in buffer to process initial_value is the results of previous cre calculations that will allow the buffer crc to be computed in stages if necessary If this is not necessary then set initial_value to 0 xj unsigned int crcl char string unsigned int length unsigned int ival buffer address to compute a cre number of characters to process initial value of crc ai static unsigned int crc 1E CRC values for crcl6 routine static unsigned int crc_vals 0x0000 0xc0c1 0xc181 0x0140 0xc301 0x03c0 0x0280 0xc241 0xc601 0x06c0 0x0780 0xc741 0x0500 0xc5c1 0xc481 0x0440 Oxcc01 0x0cc0 0x0d80 0xcd41 0x0f00 0xcfc1 0xce81 0x0e40 0x0a00 Oxcacl 0xcb81 0x0b40 0xc901 0x09c0 0x0880 0xc841 0xd801 0x18c0 0x1980 0xd941 0x1b00 Oxdbcl1 0xda81 0x
23. eters inside lt gt are detailed below each message e Poll Command PRWX00 lt CR gt lt LF gt CR a carrier return character 0xD LF a line feed character OxA e Poll Response W lt Present Weather chars gt P lt precipitation rate gt S lt error and status code gt X lt carrier 1 min avg raw data gt L lt low 1 min avg raw data gt K lt particle 1 min avg raw data gt H lt high 1m in avg raw data gt T lt temperature gt lt CRC16 gt lt CR gt lt LF gt Present Weather chars value copied form sensor response for present weather chars Error and Status code value copied form sensor response for error and status code Carrier 1 min avg raw data value copied from sensor response for carrier 1 min avg raw data Low 1 min avg raw data value copied from sensor response for low 1 min avg raw data Particle 1 min avg raw data value copied from sensor response for particle 1 min avg raw data High 1m in avg raw data value copied from sensor response for high 1m in avg raw data Temperature value copied from sensor response for temperature CRC16 a cyclic redundancy check CR a carriage return character OxD LF a line feed character OxA 19 Model 6497 Present Weather and Visibility Sensor User s Manual 5 1 2 Present Weather Data Interpretation Weather Codes The poll response contains weather codes formatted in NWS type format The latest one minute weather code ww is found in bytes 3 and 4 immediately following the W p
24. he AWOS Data Collection Platform RS 485 connections are made to the Serial Sensor Interface located in the upper right side of the electronics enclosure A 3 wire connection to the AWOS Data Collection Platform DCP is used Before proceeding verify that the sensor electrical power is turned OFF 1 Y N If the shielded RS 485 cable is not already connected to the DIN rail connector and the Serial Interface Processor connect the WHITE RS 485 signal cable to terminal 6 connect the BLACK RS 485 signal cable to terminal 7 and connect the RED GND signal cable to terminal 8 of the DIN rail terminal block Feed the free end of the shielded RS 485 cable through the serial cable gland shown in Figure 9 Strip and tin the ends of the wires 4 Route the cable through a cable gland on the DCP and connect the three wires inside the DCP 4 3 2 to TB4 pins 1 WHITE 2 BLACK and 7 RED Ensure that none of the wires are stressed then hand tighten the gland seals on the DCP enclosure and on the electronics enclosure Connecting the Sensor to the AC Power Line Connections are made to the AC interface module inside the electronics enclosure AC power connections are made to the AC Interface Board located in the lower center of the electronics enclosure A 3 wire single phase AC source is required consisting of hot neutral and earth ground connections Ea LP Install a conduit fitting at the location shown
25. hese components make up the sensor head e Transmitter gt Infrared LED gt Heated transmitter optical lens assembly e Receiver gt Heated receiver optical lens assembly gt Photo detector and preamplifier assembly e Integral Cables gt One external cable for connection to electronics enclosure gt Ground lug for electrical grounding The transmitter portion of the sensor head uses an infrared LED as a light source that is modulated to eliminate interference in the system caused by background light The LED has a very long life time has a relatively low power draw is invisible to the eye and presents no radiation hazard to the user The LED is housed in the smaller of the sensor head boxes A lens is used to collimate the LED s carrier wave modulated light into a slightly diverged beam The transmit and receive lenses are heated by dual self regulating positive temperature coefficient thermistors to a temperature just above the ambient temperature to reduce dew frost and snow on the lenses The larger sensor rectangular box houses the in beam receive optics for present weather sensing the off axis receive optics for visibility sensing and associated photo diodes and preamplifier electronics As shown in Figure 3 1 1 the in beam light passes through a horizontal line aperture to increase the 5 Model 6497 Present Weather and Visibility Sensor User s Manual precipitation detection sensitivity to particles falling vertically
26. lace marker NWS WX Code Description WX Code NWS WX Code Description Light Drizzle I Light Ice Pellet Moderate Drizzle I Moderate Ice Pellet Heavy Drizzle I Heavy Ice Pellet Light Rain A Light Hail Moderate Rain A_ Moderate Hail Heavy Rain A Heavy Hail Light Precipitation E No Precipitation Moderate Precipitation Start up code Heavy Precipitation ER Error Condition Light Snow CL Lenses need to be cleaned Moderate Snow only reported when no Heavy Snow precip Freezing Drizzle Freezing Rain The _ underline character above represents an ASCII underline character The code will be output in this and other data fields during the first 60 seconds or so after reset or power up of the sensor Note AWOS installations with a Present Weather Sensor will also report fog freezing fog haze and mist This information does not originate with the 6497 sensor but is derived from inputs from other sensors 20 Model 6497 Present Weather and Visibility Sensor User s Manual Status Codes The status codes are a convenient way for the sensor to report sensor condition and identify faulty subassemblies The status field denoted by s s s s four bytes in the data output format is a four byte field of sensor status bytes The codes can be interpreted as shown in the table below S ss ss BYTE 10 11 12 13 14 BIT STATUS BIT STATUS BIT STATUS BIT STATUS 0 OK 0 OK 0 OK 0 OK 1 FRU2 1 FRU1 1 1 2 2
27. ntamination sources as possible The Model 6497 Present Weather and Visibility Sensor is packed in two heavy walled corrugated cartons One carton contains the electronics enclosure and the larger narrow carton contains the sensor head and cables Also packed in this carton are the sensor head U bolt mounting hardware and electronics enclosure mounting hardware When opening the cartons be careful to avoid spilling the contents CAUTION Exercise care when removing the sensor head from its packing carton The temperature probe at the bottom of the sensor head extends out a short distance and can break easily Report any shortages or shipping damage to All Weather Inc within 3 days CAUTION Do NOT drill holes in any portion of the sensor head or electronics enclosure Doing so will void the warranty and may allow water to enter the enclosure Site Preparation 1 Choose the site using the guidelines in Section 4 2 1 2 Following applicable electrical and building codes install a concrete mounting base mast or tower AC power cable RS 485 signal cable and ground rod 10 Model 6497 Present Weather and Visibility Sensor User s Manual 4 2 2 Mount the Sensor Head The sensor must be securely installed and correctly oriented to work properly 1 POLE CAP CABLES TO CONTROL BOX Figure 3 Mounting Present Weather Sensor Head Attach the sensor head using the two U bolts to connect the mounting plate on
28. sing Model 6497 Present Weather and Visibility Sensor User s Manual Parameter Specification Mechanical Electronics Enclosure NEMA 4X fiberglass Sensor Assembly 1 5 3 8 cm dia mast coupling Mounting Electronics Enclosure Unistrut mounted 11 5 cm H x 26 7 cm W x 89 1 cm D Sensor Assembly 4 5 H x 10 6 W x 35 1 D Dimensions Electronics 36cmW x41 cmH x20 cm D Enclosure 14 W x16 H x8 D Sensor Assembly 4 5 kg 10 lb Weight Electronics Enclosure 10912210 Shipping Weight 2 boxes 14 5 kg 32 lb 29 Model 6497 Present Weather and Visibility Sensor User s Manual 8 WARRANTY Any defect in design materials or workmanship which may occur during proper and normal use during a period of 1 year from date of installation or a maximum of 2 years from shipment will be corrected by repair or replacement by All Weather Inc 30 allweatherinc All Weather Inc 1165 National Drive Sacramento CA 95818 Fax 916 928 1165 Phone 916 928 1000 Toll Free 800 824 5873 6497 001 Revision A June 2012
29. urces will help insure good sensor performance In general the sensor should be located on level or slightly sloping ground where the sensor site will be exposed to the same environment as the area around it Ideally the area around the site should be free of buildings trees and other obstructions All Weather Inc recommends that the siting and installation follow the general guidelines established by the Office of the Federal Coordinator for Meteorology OFCM The Federal Standard for Siting Meteorological Sensors at Airports OFCM document FSM S4 1987 makes the following recommendations 1 Distance from Obstructions The distance between the sensor and obstructions such as trees or buildings should be at least 2 times the height of the obstruction on all sides For example if a tree 20 m high is located alongside the sensor the sensor should be at least 40 m away from the tree This restriction reduces the affects of wind turbulence created by the nearby obstruc tion and makes the precipitation measurement more representative Do not locate the sensor where tree branches or wires will hang over the sensor 2 Separation from Turbulence and Contamination Sources Do not mount the sensor near building exhaust vents strobe lights or sources of smoke or steam Where possible locate the unit as far away from runways and roads as possible to reduce optics fouling from wind blown road dirt An ideal minimum distance is at least 3
30. ure Secure the cable to the mast using tie wraps or other straps 1 Route the cable from the sensor head into the electronics enclosure as shown in Figure 9 2 Connect the wires to the connector on the DIN rail shown in Figure 10 according to the wiring diagram in Figure 11 15 Model 6497 Present Weather and Visibility Sensor User s Manual Figure 10 shows the layout of the various electronics subassemblies inside the electronics enclosure SERIAL SENSOR INTERFACE EMI PPP PERISICS FILTER TE E EA IN Figure 10 Model 6497 Present Weather and Visibility Sensor Subassemblies Inside Enclosure 16 Model 6497 Presert Weather and Visibility Sensor User s Manual Figure 11 summarizes all the signal and power wiring for the Model 6497 Present Weather and Visibility Sensor Sensor pilla pd Board Function Color 4 RS 485 GREEN 5 RS 485 BROWN 6 GROUND BLACK 7 DC RED AC more ean Function Color 1 HOT BLACK 2 NEUTRAL WHITE 3 GROUND GREEN 6497 PRESENT WEATHER VISIBILITY SENSOR FITTING M404802 CONDUIT 1 POWER INTERFACE 2 BOARD SENSOR INTERFACE PROCESSOR HOO0OO0OO0OO0OO DC AND DC CONNECTIONS REFER TO DC POWER SUPPLY HEADER J2 M438210 POWER SUPPLY Figure 11 Model 6497 Present Weather and Visibility Sensor Signal and Power Wiring 17 Model 6497 Present Weather and Visibility Sensor User s Manual 4 3 1 RS 485 Connections to t
31. zontal 4 The sensor head is generally oriented with the transmitter head on the north side in the Northern hemisphere so that the receiver optics face north Align the sensor head so that the receive lens faces north If the orientation can be altered to either side of north to obtain a view with fewer or more distant obstructions it is generally acceptable to alter the orientation up to 30 degrees from north 5 General Recommendations e The sensor must be mounted vertical within 2 degrees so that the line aperture on the in beam lens is horizontal e The sensor is generally oriented with off axis lens facing away from highway or contamination sources to avoid dirt splash directly into the lenses e The sensor should be oriented to avoid direct sunlight shining into the off axis lens SUGGESTION Take a picture at the installation site in each direction north east south and west to record the topography and obstructions for future reference Model 6497 Present Weather and Visibility Sensor User s Manual 4 2 MECHANICAL INSTALLATION 4 2 1 Preparation The sensor and site should be readied prior to beginning the installation SITING GUIDELINES Sensor head mounted 2 5 m above ground Rigid mounting pole In beam lens aperture horizontal to 2 degrees No overhanging trees wires or roof lines Distance between sensor and closest obstruction at least 2 times obstruction height As far from road runway and co
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