SR50A Sonic Distance Sensor
Rugged acoustic distance sensor
Typically used for snow depth or water depth measurements
weather applications supported water applications supported energy applications supported gas flux and turbulence applications supported infrastructure applications supported soil applications supported

Overview

The SR50A Sonic Distance Sensor provides a non-contact method for determining snow or water depth. It determines depth by emitting an ultrasonic pulse and then measuring the elapsed time between the emission and return of the pulse. An air temperature measurement is required to correct for variations of the speed of sound in air. 

Note: Campbell Scientific recommends model SR50A-EE-L for operation in extreme environmental conditions where corrosion is a concern (such as coastal regions).

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Benefits and Features

  • Wide operating temperature range
  • User-selectable options for output
  • Rugged enough for harsh environments
  • Uses a multiple echo processing algorithm to help ensure measurement reliability
  • Compatible with most Campbell Scientific data loggers

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Specifications

Measurement Time < 1.0 s
Measurement Range 0.5 to 10 m (1.6 to 32.8 ft)
Output Options SDI-12 version 1.3, RS-232, RS-485 (output options selected by configuring internal jumpers)
Baud Rates 1200 to 38400 bps (RS-232, RS-485 modes)
Power Requirements 9 to 18 Vdc (typically powered by data logger’s 12 Vdc power supply)
Beam Acceptance ~30°
Resolution 0.25 mm (0.01 in.)
Accuracy ±1 cm (0.4 in.) or 0.4% of distance to target (whichever is greatest). Requires external temperature compensation.
Operating Temperature Range -45° to +50°C
Compliance CE Compliant
Length 10.1 cm (4.0 in.)
Diameter 7.5 cm (3 in.)
Cable Weight 250 g (8.2 oz) for a 4.57-m (15-ft) cable
Weight
  • 375 g (13.2 oz) without cable
  • 1.0 kg (2.2 lb)

Maximum Cable Length
-NOTE- Cable lengths greater than 60 m require a heavier gage wire if the power supply drops below 11 Vdc.
SDI-12 60 m (200 ft)
RS-232 60 m (200 ft)
Baud rates ≤ 9600 bps
RS-485 300 m (984 ft)

Power Consumption
Active 250 mA (typical)
Quiescent SDI-12 Mode < 1.0 mA
Quiescent RS-232/RS-485 Modes
  • < 1.25 mA (≤ 9600 bps)
  • < 2.0 mA (> 9600 bps)

Compatibility

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.

Data Loggers

Compatible Note
21X (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR10 (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR1000 (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR1000X SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR10X (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR200X (retired) SDI-12
CR206X (retired) SDI-12
CR23X (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR295X (retired) SDI-12
CR300 SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR3000 SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR310 SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR500 (retired) SDI-12
CR5000 (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR510 (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR6 SDI-12, RS-232, and RS-485
CR800 SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR850 SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR9000 (retired)
CR9000X (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.

Distributed Data Acquisition

Compatible Note
GRANITE 6 SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.

Additional Compatibility Information

Data Logger Considerations

One single-ended channel per probe is required; an excitation channel can be shared by several probes.

Downloads

SR50A/AT OS v.1.3 (52 KB) 22-08-2007

Current SR50A / AT firmware.
View Revision History

SR50A example programs v.1 (11 kB) 22-01-2020

CR6 and CR1000X programs that directly read each type of SR50A output (SDI-12, RS-232, RS-485), and a CR1000 program that reads the RS-485 output using an MD485 Multidrop interface. A 107 sensor provides the temperature measurement needed for temperature compensation. The programs use the data filtering method described in the manual.

FAQs for

Number of FAQs related to SR50A: 17

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  1. Can the range operation of the SR50A-L be increased?

    No.

  2. To replace the transducer heads on an SR50A-L, is there a torque specification for the screws?

    No.

  3. What is the maximum cable length available for the SR50A-L?

    Approximately 800 feet. This is a function of the limitations of the SDI-12 signal.

  4. Can an SR50A-L be connected to a data logger on an SDI-12 port?

    Yes. This sensor has an SDI-12 output.

  5. Can the SR50A-L handle a coastal environment with humidity and salt spray?

    This sensor requires regular maintenance in a marine environment. The SR50A-L functions properly if care is taken to keep the vent free of salt accumulation and the interior free of moisture by replacing the desiccant as needed. It may also be necessary to carefully clean the face of the sensor to remove salt deposits.

  6. Can an SR50A-L be used to measure stream flow depth of small ephemeral creeks?

    Yes. The accuracy of the sensor is 1 cm or 0.4% of distance to water (whichever is greater). As long as the water level is deeper than this, the water height can be confidently determined.

  7. Can an SR50A-L be used to measure the depth of a body of saltwater?

    Yes, but more routine maintenance of the sensor is needed in marine environments.

  8. What is the potential error over a range of cold and warm temperatures with the SR50A-L if no temperature compensation calculation is applied to the measurement?

    The potential error is roughly ±0.4% of distance for a ±25° Celsius variation away from 0° Celsius.

  9. Can the SR50A-L be recalibrated?

    The sensitivity can be adjusted slightly at the factory, but it cannot be recalibrated. Typically, the transducing diaphragm needs to be replaced periodically to maintain calibration. This can be done by the user or at the factory.

  10. Can the SR50A-L be used in small-diameter wells?

    No. This causes echoes and reflections that confuse the sensor.