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Campbell SR50 Instruction Manual
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Campbell SR50 Instruction Manual

Sonic ranging sensor
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SR50
Sonic Ranging Sensor
April 2013
Copyright © 2009 - 2013
Campbell Scientific (Canada) Corp.

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Summary of Contents for Campbell SR50

  • Page 1 SR50 Sonic Ranging Sensor April 2013 Copyright © 2009 - 2013 Campbell Scientific (Canada) Corp.

  • Page 3: Table Of Contents

    SR50 Sonic Ranging Sensor Table of Contents 1. SR50 Specifications ............. 3 2. Introduction ..............4 3. Operation (General) ............. 4 C4A  5AB &(* %$44444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444F C4B  5AB A@<= (%(# .#&"444444444444444444444444444444444444444444444444444444444444444444444I C4C +") ( $ +*&+*44444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444 AB C4D -% BA (%(# .#&") %( +") ( $ +*&+* 444444444444444444444444444444 AD +*&+*44444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444 B@...
  • Page 4 SR50 Sonic Ranging Sensor Tables A4 E@  5AB %##$ )*44444444444444444444444444444444444444444444444444444444444444444444444444444444444AA ()) +#&( ** $) %( +") ( $ $  +*&+*) 444444444444444444BA Appendices A. Making Concurrent Measurements with the SR50 ..32...

  • Page 5: Sr50 Specifications

    SR50 Sonic Ranging Sensor SR50 Sonic Ranging Sensor 1. SR50 Specifications Power Requirements: 9-16 VOLTS D.C. Power Consumption: 2 mA (Quiescent) 250 mA (Measurement Peak) Measurement Time: 0.6 seconds typical 3.0 seconds max. Output: SDI-12 (version 1.2) Serial ASCII - 300 and 1200 Baud TTL or RS232...

  • Page 6: Introduction

    A simple calculation is applied to initial readings for this purpose. The SR50 is capable of picking up small targets or targets that are highly absorptive to sound--such as low density snow. The SR50 can measure multiple targets and it makes use of a unique echo processing algorithm to help ensure measurement reliability.
  • Page 7 The SR50 bases every measurement on several readings and applies an algorithm to improve measurement reliability. When using SDI-12 or ASCII output, up to 3 targets can be detected with the SR50 provided the difference between their height is > 0.4 meters.
  • Page 8 CR500, CR510, CR23X, CR1000 and BDR320 have the capability to read SDI-12 sensors (CR10’s with the correct PROM can do SDI-12). The SR50 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 9 The SDI-12 protocol has the ability to support various measurement commands. The SR50 supports the commands that are listed in Table 1. Depending on the application, different measurement commands may be selected. The different commands are entered as options in Parameter 2 of instruction 105.
  • Page 10 If the SR50 is unable to detect a proper echo for a measurement, the sensor will return a zero value for the distance to target value. When...
  • Page 11 6: 273.15 Offset ; This converts the value to degrees Kelvin. ; Measure the SR50 using code ‘1’ for parameter 2. This will cause the SR50 to measure the distance to target (in meters) and provide a measurement quality number.
  • Page 12 SR50 Sonic Ranging Sensor 7: Z=X+F (P34) 1: 2 X Loc [ DEPTH 2: 2.0 <<<<<< Insert the distance from sensor to bare ground 3: 2 Z Loc [ DEPTH ] ; This is actual snow depth. ; Hourly data output…...
  • Page 13 Start Verification calculates NUMERIC SIGNATURE ROM Signature Send Identification 012CAMPBELLSR50 1.1 NOTE: There are 2 spaces between SR50 and 1.1 Concurrent Measurement* Concurrent Measurements* Same as M – M8 Where a = address of SDI-12 device. Where n = numbers 1 to 8.
  • Page 14 Enable Line is pulsed high to +5 Volts. The pulse width should be a minimum of 5 ms and a maximum of 250 ms in width. When the SR50 detects that the Sensor Enable Line is high, it makes a measurement.
  • Page 15 SR50 Sonic Ranging Sensor 3.3.1 Pulse Train Wiring *"%( %"%( +$* %$ %$$* %$ "! (%+$ (%+$ < = JAB JAB ($ * +) +") $$"  * $)%( $" %$*(%" %(* "(  " (%+$ < = FIGURE 3. Pulse Train Wiring CAUTION The order in which the connections are made is critical.
  • Page 16 The programming examples assume that the sensor is mounted 2 meters above the ground and the desired output is snow depth in meters. In these examples a 21X micrologger is used to read the SR50 with the pulse train option. The number of pulses are counted on Pulse channel 1.
  • Page 17 SR50 Sonic Ranging Sensor The following instructions set the sensor enable line high long enough for the SR50 to detect it, then set it low. 1: Set Port (P20) 1: 1 Set High 2: 1 Port Number 2: Excitation with Delay (P22)
  • Page 18 SR50 Sonic Ranging Sensor 8: Z=SQRT(X) (P39) 1: 24 X Loc [ ATempComp ] 2: 24 Z Loc [ ATempComp ] 9: Z=X*Y (P36) 1: 21 X Loc [ Dis2Surf ] 2: 24 Y Loc [ ATempComp ] 3: 21...
  • Page 19 3.4.2 Pulse Train Programming Example 2 Example 2 will measure every execution interval. This program will measure the SR50 when Flag 1 is set high, which can be done manually and/or at a specified interval. All instructions above those that define the Output Interval must remain together. Note that in this example the datalogger program executes every 10 seconds, but the SR50 measures and processes only every 15 minutes.
  • Page 20 SR50 Sonic Ranging Sensor If Flag 2 is high, compute the air temperature compensation factor and correct the distance-to-surface measurement for air temperature (see Formula 1). 3: If Flag/Port (P91) 1: 12 Do if Flag 2 is High 2: 30...
  • Page 21 SR50 Sonic Ranging Sensor Parameter 2 of P92 determines how often to measure. 12: If time is (P92) 1: 0 Minutes into a 2: 15 Minute Interval 3: 11 Set Flag 1 High 13: If Flag/Port (P91) 1: 11 Do if Flag 1 is High...
  • Page 22 Sensor Enable Line high to +5 Volts. The pulse width should be a minimum of 5 ms and a maximum of 250 ms. Once the SR50 detects the Sensor Enable Line has gone high, it makes a measurement. When the measurement is finished, the SR50 outputs the appropriate serial data.

  • Page 23: Sensor Mounting And Installation

    22 degrees. This means that no objects should obstruct the intended target within this 22 degree beam. If an obstruction is within this beam angle the SR50 may detect the unwanted object instead of the intended target. By inserting a height value in Formula 2, a Clearance Radius in the same measurement units as the height can be obtained.
  • Page 24 The SR50’s mounting stem (1.25” outside diameter) enables various installation options. A 3/4” x 1” pipe crossover (model L1049, 1.25” x 1” inside diameter) enables the SR50 to mount to any 3/4” pipe (1” outside diameter). The SR50’s mounting stem also has 1” pipe thread to accommodate other threaded installation options.
  • Page 25 Some errors that are associated with the measurement are a percentage of the distance to target. As a result, the closer the SR50 is to the target the lower the absolute errors will be. However, the SR50 should not be mounted closer than 0.5 meters to target.

  • Page 26: Data Interpretation

    One such example is snow of extremely low density. In this situation, the surface may not reflect enough sound for the sensor to detect. The SR50 will output zero for the distance to target or a single pulse in the pulse output mode. Zero measurements will likely cause problems in processed data output (e.g., averages, minimum) of averaging scheme...

  • Page 27: Maintenance

    The quality numbers can vary from 162 to 600. A quality number between 162 and 210 indicates that the SR50 detected a solid target. A number between 210 and 300 is an indication that the target is not definitive and a number between 300 and 600 is an indication that the target is of poor quality (see section 3.0...

  • Page 28: Assembly/Disassembly Procedures

    It is also recommended that the datalogger program be saved. If the sensor is in operation, always disconnect the SR50 from the datalogger before disassembling. Refer to Section 3.1.1 or 3.3.1, Wiring for further information on your specific wiring connection and disconnection.
  • Page 29 SR50 Sonic Ranging Sensor 2. Remove the transducer housing from the main cylinder housing and unplug the white connector, as indicated below. Pull only on the connector and not the wires. 3. Remove the dessicant packs by undoing the twist tie that holds them in place and dispose of the packs appropriately.
  • Page 30 SR50 Sonic Ranging Sensor 7. Insert the washer, the new transducer assembly and small O- ring in the reverse order of removal and re-attach the retaining bar with the 2 Phillips screws that were set aside in step 4. NOTE: Do not over tighten the screws when reassembling, as over tightening will cause the transducer to bend.

  • Page 31: Changing The Address/Option Jumpers

    SR50 Sonic Ranging Sensor 15. Insert the new large O-ring on the aluminium end plate, ensuring that it is properly seated in the SR50 housing as shown below. O-ring 16. Plug the new transducer into the white connector and attach it to the main housing with the four Phillips screws that were removed in Step 1.
  • Page 32 SR50 from the lid and slide the cylinder off, as shown below. The internal jumpers are now exposed to set the address or to change the sensor's output options. FIGURE 8: SR50 Stuffing Chart/Jumper Settings (address 15 for factory use only)
  • Page 33 2 Philips screws that were set aside in Step 2. 8. Replace the large O-ring on the aluminium end plate, ensuring that it is properly seated in the SR50 housing as shown below, and then re-attach the transducer assembly to the main housing cylinder.
  • Page 34 SR50 Sonic Ranging Sensor Appendix A. Making Concurrent Measurements with the SR50 %$+(($* )+(#$*  " */ ""%-) * *"% $ )/)*# *% $ * * #)+(#$*) $  5AB , ) $ %$* $+ &(%)) $ *) &(%(# - *%+* - * $ %(  ( $ (%# *  5AB , 4 $ * )$)%( )  ,"...
  • Page 35 X Loc [ AIR_TEMP ] 2: 273.15 F 3: 2 Z Loc [ T_KELVIN ] ; Measure the SR50 using Concurrent Measurement ability... 3: SDI-12 Recorder (P105) 1: 0 SDI-12 Address 2: 1 -- Start Measurement (aM1!) ; distance with echo quality numbers and concurrent- 3: 1 Port ;...
  • Page 36 SR50 Sonic Ranging Sensor 4: If (X<=>F) (P89) 1: 3 X Loc [ Raw_Dist ] 2: 3 >= 3: -1000 F 4: 30 Then Do 5: Z=X (P31) 1: 3 X Loc [ Raw_Dist ] 2: 8 Z Loc [ DEPTH...
  • Page 37 SR50 Sonic Ranging Sensor 2: 0 Exponent of 10 3: 6 Z Loc [ REF_TEMP ] 17: Z=X/Y (P38) 1: 2 X Loc [ T_KELVIN ] 2: 6 Y Loc [ REF_TEMP ] 3: 7 Z Loc [ MULT 18: Z=SQRT(X) (P39)
  • Page 38 SR50 Sonic Ranging Sensor This page intentionally left blank...
  • Page 39 Campbell Scientific Canada Corp. | 11564 149 Street | Edmonton AB T5M 1W7 | 780-454-2505 | www.campbellsci.ca AUSTRALIA | BRAZIL | CANADA | COSTA RICA | ENGLAND | FRANCE | GERMANY | SOUTH AFRICA | SPAIN | USA...