Campbell SR50A Instruction Manual
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Campbell SR50A Instruction Manual

Sonic ranging sensors
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SR50A and SR50AT
Sonic Ranging Sensors
2016
Copyright © 20 16
Campbell Scientific (Canada) Corp.

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  • Page 1 SR50A and SR50AT Sonic Ranging Sensors 2016 Copyright © 20 16 Campbell Scientific (Canada) Corp.
  • Page 2 SR50A Sonic Ranging Sensor Warning! Always disconnect the sensor before opening. Avertissement! Toujours débrancher le capteur avant de l'ouvrir. This Device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) This device must accept any interference received, including interference that may cause undesirable operation.
  • Page 3 WARRANTY AND ASSISTANCE This equipment is warranted by CAMPBELL SCIENTIFIC (CANADA) CORP. ("CSC") to be free from defects in materials and workmanship under normal use and service for ***** twenty-four (24) months from date of shipment unless specified otherwise. ***** Batteries are not warranted.

  • Page 4: Table Of Contents

    TABLE OF CONTENTS Specifications ........................4 Introduction ........................6 Operation .......................... 7 Quality Numbers ......................7 Temperature Compensation for SR50A version ............8 Temperature Compensation for SR50AT version ............9 SDI-12 Operation ..................... 10 3.4.1 SDI-12 Wiring ....................10 3.4.2 SDI-12 Addresses .....................
  • Page 5 Figure 5 SR50A Mount - mounted parallel to pipe ..............30 Figure 6 SR50A Mount - mounted perpendicular to pipe ............30 Figure 7 SR50A - mounted using Nurail and C2151 mounting stem ........31 Figure 8 Disconnect cable from sensor ................... 33 Figure 9 Remove 6 screws from the transducer housing ............

  • Page 6: Specifications

    SR50A Sonic Ranging Sensor 1 Specifications Power Requirements: 9-18 VOLTS D.C. Power Consumption: Quiescent SDI-12 Mode < 1.0mA Note1 RS-232/RS485 Mode < 2.25mA Peak Measurement Current 250 mA typical Measurement Time: Less than 1.0 second Selectable Outputs: SDI-12 (version 1.3)
  • Page 7 SR50A Sonic Ranging Sensor Weight: Aluminum chassis: 375g (13.2oz) Stainless steel chassis: 795g (28oz) Cable (SR50A) 15 feet: 0.25kg (0.55lbs) Temperature Measurement (SR50AT): 0°C to +50°C ±0.2°C -45°C to 0°C ±0.75°C IP Rating Electrical Housing IP67 Transducer IP64 Note 1: The quiescent current draw is less than 1.25mA if the BAUD rate is 9600 BAUD or less.

  • Page 8: Introduction

    SR50AT to output temperature compensated values. The SR50A is capable of picking up small targets or targets that are highly absorptive to sound, such as low density snow. The SR50A makes use of a unique echo processing algorithm to help ensure measurement reliability.

  • Page 9: Operation

    Unwanted objects must be outside the field of view. If a target is in motion, the SR50A may reject a reading if the target distance changes at a rate of 4 centimetres per second or more.

  • Page 10: Temperature Compensation For Sr50A Version

    3.2 Temperature Compensation for SR50A version The SR50A version of the sensor does not include a temperature sensor to compensate the speed of sound for variations in air temperature. Temperature corrections for the speed of sound will need to be applied to the readings in either post processing or by the measurement/monitoring device.

  • Page 11: Temperature Compensation For Sr50At Version

    SR50A Sonic Ranging Sensor formula is not applied, the distance values will not be accurate for temperatures other than 0°C. 3.3 Temperature Compensation for SR50AT version The SR50AT version of the sensor includes a temperature sensor to compensate the speed of sound for variations in air temperature.

  • Page 12: Sdi-12 Operation

    3.4.1 SDI-12 Wiring It is recommended to power down your system before wiring the SR50A. Never operate the sensor with the shield wire disconnected. The shield wire plays an important role in noise emissions and susceptibility as well as transient protection.

  • Page 13: Sdi-12 Addresses

    SR50A Sonic Ranging Sensor 3.4.2 SDI-12 Addresses The SR50A can be set to one of ten addresses (0 to 9) which allows up to ten sensors to be connected to a single digital I/O channel (control port) of an SDI-12 datalogger.
  • Page 14 SR50A Sonic Ranging Sensor command in SDI-12 mode or by using the setup menu in RS- 232 or RS-485 modes. - 12 -...
  • Page 15 Address Query aAb! Change Address command b is the new address aXM;D.DDD! Set the distance to ground parameter in the SR50A. The distance Extended must be in meters with no more than 3 decimal places. Address is returned command aXI;DDD.DD! Set the distance to ground parameter in the SR50A.

  • Page 16: Rs-232 Operation

    3.5 RS-232 Operation The SR50A sensor comes from the factory with the internal jumpers set to SDI-12 mode. To use the SR50A in the RS-232 mode of operation the jumpers will need to be set as outlined in Section 7.

  • Page 17: Rs-485 Operation

    3.6 RS-485 Operation The SR50A sensor comes from the factory with the internal jumpers set to SDI-12 mode. To use the SR50A in the RS-485 mode of operation the jumpers will need to be set as outlined in Section 7.

  • Page 18: Rs-232 And Rs-485 Settings

    BAUD rate is changed the new BAUD rate must be used for further communications to the SR50A. It is important to keep track of the BAUD rate setting on the SR50A. If the BAUD rate setting is unknown, we recommend trying the default value of 9600 BAUD.
  • Page 19 SR50A Sonic Ranging Sensor When the hyperterminal session is started the command “SETUP” needs to be entered. Hitting the Enter will transmit the CR LF characters which are required after the text “SETUP”. The text “SETUP” is not case sensitive so any combination of upper and lower case letters will work.

  • Page 20: Baud Rate Setting

    SR50A Sonic Ranging Sensor The following is a summary of settings that can be changed on the SR50A RS-232 or RS-485 operating modes. Setting Description Options Default Value BAUD Rate 1200 9600 BAUD 4800 9600 19200 38400 Address RS-232/RS-485 Any 2 Alphanumeric...

  • Page 21: Address

    1.5 and 2.25 mA for the BAUD rates of 19200 or 38400 respectively. It is possible to download a firmware update to the SR50A via the RS-232 or RS-485 communication interface. Higher BAUD rates may be desirable to speed up this process.

  • Page 22: Auto Measure Auto Output Mode

    SR50A Sonic Ranging Sensor 3.7.3.2 Auto Measure Auto Output Mode In this mode the SR50A will automatically exit its low power mode, initiate a measurement and output the data. The frequency by which the SR50A will perform this is set by adjusting the Measurement Interval Units and the Measurement Interval Value parameters.

  • Page 23: Distance To Ground

    SR50A Sonic Ranging Sensor Do not use this option on the SR50A sensor unless the SR50A is sent valid temperature reading via the Temperature Input command. 3.7.5 Distance to Ground A valid distance to ground must be entered when the SR50A is configured to output snow depth values.

  • Page 24: Output Unit

    SR50A Sonic Ranging Sensor 3.7.8 Output Unit The SR50A always outputs the distance to the target. The units for the distance value can be set to any of the following values: Meters Centimeters Millimeters Feet Inches 3.7.9 Quality Output The SR50A quality numbers can be optionally included in the data output string.

  • Page 25: Poll Command

    “i33<CR>” – information command with factory address of 33 3.8.4 Temperature Input command The temperature input command is used to send the SR50A version of the sensor a temperature value that is to be used for temperature compensation. The value sent must be in degrees Celsius and should not exceed 8 characters.

  • Page 26: Rs-232/Rs-485 Data Output Format

    33 and a temperature value in Celsius. 3.9 RS-232/RS-485 Data Output Format 3.9.1 Measurement Output The measurement output string for the SR50A is as follows: <STX>aa;D.DDD;QQQ;TT.TT;VVVVV;CC<CR><LF><ETX> <STX> is the hex character 0x02 (2 in decimal) These two characters are the serial address of the sensor. The default is 33.
  • Page 27 SR50AT sensor. This value is optionally output by setting the Temperature Output option to ON. Only the SR50AT sensor will output a valid temperature. The SR50A will output a – 999.00 if the Temperature Output option is set to ON. The temperature is displayed with 2 decimal points of precision.

  • Page 28: Information Message Output

    End of transmission character. 0x03 in hexadecimal or 3 in decimal 3.9.2 Information Message Output The measurement output string for the SR50A is as follows: <STX>aa;SSSSS;H.H;F.F;BBBBB;WWWWW<CR><LF><ETX> <STX> is the hex character 0x02 (2 in decimal) These two characters are the serial address of the sensor. The default is 33.
  • Page 29 SR50A Sonic Ranging Sensor WWWWW This is the checksum of the firmware. This is a 2 character checksum of the data packet. The checksum is the two’s complement of the data packet sum including control characters. The least significant byte is used resulting in a 2 character checksum.

  • Page 30: Sensor Mounting And Installation

    Figure 3 Beam Angle Clearance 4.2 Mounting Height Any target to the SR50A should be at least 50cm or more from the face of the transducer. An attempt should also be made to not mount the sensor too far from the target surface. The...

  • Page 31: Reference Point

    There are two standard mounting options supplied for the SR50A sensor. The first is the SR50A Mount. This bracket is designed to mount the SR50A parallel or perpendicular to a pipe. Figure 5 demonstrates the parallel mounting method uses 2 band clamps to secure the bracket to the pipe.

  • Page 32: Figure 5 Sr50A Mount - Mounted Parallel To Pipe

    (part# C2151) and a Nurail. The mounting stem is sized to fit a 1” Nurail (L1049). This mounting method was used for the SR50 (predecessor to the SR50A) and the stem can be used to fit the SR50A into existing SR50 mounts.

  • Page 33: Figure 7 Sr50A - Mounted Using Nurail And C2151 Mounting Stem

    SR50A Sonic Ranging Sensor Figure 7 SR50A - mounted using Nurail and C2151 mounting stem SR50A with 6-plate gill radiation shield – the picture below shows the SR50A stem attachment - 31 -...

  • Page 34: Maintenance

    Once the desiccant becomes saturated the color will change from blue to pink. If the SR50A is used in humid environments, the desiccant should be replaced more frequently.

  • Page 35: Disassembly/Assembly Procedures

    It is also recommended that the datalogger program be saved. If the sensor is in operation, always disconnect the SR50A from the datalogger or the connector before disassembling. Refer to Section 3.4.1 or Section 3.5.1, Wiring for further information on your specific wiring connection and disconnection.

  • Page 36: Figure 9 Remove 6 Screws From The Transducer Housing

    SR50A Sonic Ranging Sensor Figure 9 Remove 6 screws from the transducer housing Note: The screws used on the SR50A have changed from the slotted type to Philips. - 34 -...

  • Page 37: Figure 10 Remove Transducer Housing And Disconnect Wires

    SR50A Sonic Ranging Sensor Figure 10 Remove transducer housing and disconnect wires Figure 11 Location of Desiccant in transducer housing assembly - 35 -...

  • Page 38: Figure 12 Remove And Replace Desiccant

    SR50A Sonic Ranging Sensor Figure 12 Remove and Replace Desiccant Figure 13 Remove the 2 flat Philips screws to expose the PCB Carefully reassemble in reverse order. - 36 -...

  • Page 39: Jumper Settings

    3 jumpers and never mix the jumpers amongst the SDI-12, RS-232 or RS-485 locations. The other jumper located on the SR50A places the sensor in either the normal operation mode or in the Program update mode. The program mode is only used for updating the internal firmware of the sensor.

  • Page 40: Sr50A Firmware Updates

    SR50A Sonic Ranging Sensor 8 SR50A Firmware Updates The firmware on the SR50A can be updated by using a terminal program such as Hyperterminal. If your SR50A is configured for RS-232 communications, the SR50A can be programmed from the I/O cable. The SR50A also contains an internal female DB-9 connector.
  • Page 41 SR50A Sonic Ranging Sensor Power can now be applied to the SR50A by connecting the connector and applying power to the sensor. The Green LED should remain on when powered up properly. Setup Hyperterminal or the communications program that you are using as follows:...

  • Page 42: Data Interpretation & Filtering

    9.2 Data Filtering There are scenarios where the SR50A can produce values with higher than expected errors. For example in really low density snow very little echo is returned back to the sensor. The increase in Echo quality numbers in an indication of the weak signals.
  • Page 43 (median) value is selected. 'CR1000 Series Datalogger 'This program example is written for use with an SR50A. This will require the use 'of an external Air Temperature measurement (i.e. AirTC). 'Const Dist2Gnd should be set equal to the distance between the bottom of the ' SR50A and the ground, in meters.
  • Page 44 ' Measure Battery Voltage and Internal Temperature Battery (Batt_V) PanelTemp (PTemp_C,_60Hz) 'SR50A Sonic Ranging Sensor (SDI-12 Output) measurements: 'Take snow depth measurement every hour during last minute or if manual flag is true. 'This interval can be changed to different application requirements.

  • Page 45: Datalogger Program Examples

    10.1 Programming Example 1 SR50A SDI-12 “M1!” CR10X Datalogger ;{CR10X} ;In this example, the SR50A is mounted 2.5 meters above the ground. ;The CR10X sends an SDI-12 command to the SR50A, which outputs a ;non-temperature compensated distance value (Raw_Dist) and signal quality value.
  • Page 46 Loc [ T_Kelvin ] 5: 1.0 Multiplier 6: 273.15 Offset ;This converts the value to degrees Kelvin ;Use SDI-12 command "M1!" to receive Distance and Signal Quality from the SR50A 2: SDI-12 Recorder (P105) 1: 0 SDI-12 Address 2: 1...

  • Page 47: Programming Example 2

    3: 1 Port ;Use Ports 5-8 for CR23X 4: 3 Loc [ SR50ATDIS ] 5: 1.0 Multiplier 6: 0.0 Offset ;Set the initial distance from the SR50A to the ground in meters: 2: Z=F x 10^n (P30) - 45 -...

  • Page 48: Programming Example 3

    9: Sample (P70) 1: 1 Reps 2: 5 Loc [ SR50AT_T ] *Table 2 Program 02: 0.0000 Execution Interval (seconds) *Table 3 Subroutines End Program 10.3 Programming Example 3 SR50A SDI-12 “M1!” CR1000 Datalogger 'CR1000 Series Datalogger - 46 -...

  • Page 49: Programming Example 4

    (SR50(),1,0,"M1!",1,0) 'Measure the 107 temperature sensor: Therm107 (Air_Temp,1,1,Vx1,0,250,1.0,0) 'Use Air_Temp to calculate corrected distance: Temp_Corr_Distance=Raw_Dist*(SQR((Air_Temp+273.15)/273.15)) 'Subtract the corrected distance from the initial distance of the SR50A to the ground: Snow_Depth=Initial_Distance-Temp_Corr_Distance 'Call Data Table and Store Data: CallTable (Table1) NextScan EndProg 10.4 Programming Example 4...
  • Page 50 'This program is written for the SR50AT version only. For an SR50A 'sensor a valid depth can not be output unless a temperature value 'is passed from the datalogger to the SR50A via the extended SDI-12 command 'Declare Public Variables...

  • Page 51: Programming Example 5

    'Convert the floating point value to a text string for the SDI-12 command XtendedDistValStr = FormatFloat (NewDistanceToGround,"%4.3f") 'To send the Distance to ground (in meters) value to the SR50A the 'SDI-12 extended command is as follows: 'aXDM.MMM!- where D.DDD is the value such as 2.345 Meters SDI12commandstring = "XM;"...
  • Page 52 'The SR50A is used in RS-232 mode (internal jumpers are set). 'The CR1000 sends a serial string to the SR50A, which is in "Measure on Poll Mode", 'and then receives a serial string in return which is parsed into different values.

  • Page 53: Programming Example 6

    SR50A Sonic Ranging Sensor Therm107 (Air_Temp,1,1,Vx1,0,250,1.0,0) 'Use Air_Temp to calculate corrected distance: Temp_Corr_Distance=Raw_Distance*(SQR((Air_Temp+273.15)/273.15)) 'Subtract the corrected distance from the initial distance of the SR50A to the ground: Snow_Depth=Initial_Distance - Temp_Corr_Distance 'Call Data Table and Store Data: CallTable (Table1) NextScan EndProg Programming Example 6 10.6...
  • Page 54 SerialFlush (Com1) 'Recieve serial string from SR50A SerialIn (SR50AData,Com1,200,13,50) SplitStr (ParseVals,SR50AData,"",6,0) 'Subtract the corrected distance from the initial distance of the SR50A to the ground: Snow_Depth=Initial_Distance - Dist_To_Snow 'Call Data Table and Store Data: CallTable (Table1) NextScan EndProg - 52 -...

  • Page 55: Warnings/Cautions

    SR50A Sonic Ranging Sensor 11 Warnings/Cautions Never open the SR50A while the sensor is connected to power or any other device. Always disconnect the SR50A via the connector or disconnect the cable wires from their termination points. - 53 -...

  • Page 56: Appendix A: Sr50Ah Heater Option

    SR50A Sonic Ranging Sensor 12 APPENDIX A: SR50AH Heater Option 12.1 Heater Introduction The heater option on the SR50AH is intended for installations where rime ice is problematic. The heater will help to prevent the ice from forming on the transducer, which can impair proper operation of the sensor.

  • Page 57: Maintenance

    The procedure to disassemble the SR50AH for desiccant replacement or transducer replacement is as follows: Remove the 6 Philips screws on the outermost hole pattern. Note: The screws used on the SR50A have changed from the slotted type to Philips. - 55 -...
  • Page 58 SR50A Sonic Ranging Sensor Separate the housing from the sensor body and disconnect the connector from the transducer to the main sensor body. To replace the desiccant remove the desiccant holder plate with the Philips 4-40 screw. Cutting the tie strap and will allow the old packets to be removed for replacement.
  • Page 59 SR50A Sonic Ranging Sensor that the desiccant does not come in contact with the metal backing of the transducer. If only the desiccant is being inspected or replaced, step 4 and 5 are not required. Steps 4 to 6 are required to replace the transducer only.
  • Page 60 SR50A Sonic Ranging Sensor 6. Replace the transducer assembly and the second o-ring that seats under the transducer assembly. 7. Reassemble the sensor in the reverse order. Please observe the orientation of the parts, wiring and desiccant. - 58 -...
  • Page 61 SR50A Sonic Ranging Sensor Figure 15 Complete transducer assembly with power connection - 59 -...

  • Page 62: Appendix B: Optional Open Faced Transducer For Harsh Environments

    SR50A Sonic Ranging Sensor 13 APPENDIX B: Optional Open Faced Transducer for Harsh Environments 13.1 General Part # C2257 – Open Faced Transducer The Open Faced transducer provides extra corrosion protection (from various chemicals) to the gold coating of the foil.

  • Page 63: Appendix C: Sr50A-316Ss And Sr50At-316Ss Options

    The Stainless Steel option will help prevent damage to the chassis of the sensor. Two model options are available, either the SR50A-316SS or the SR50AT-316SS. Both models are identical in operational aspects to their aluminum chassis equivalent.
  • Page 64 Campbell Scientific (Canada) Corp. | 14532 131 Avenue NW | Edmonton AB T5L 4X4 | 780.454.2505 | www.campbellsci.ca AUSTRALIA | BRAZIL | CANADA | COSTA RICA | FRANCE | GERMANY | SOUTH AFRICA | SPAIN | UNITED KINGDOM | USA...

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