RETIRED ›
This product is no longer available and has been replaced by: SNOWVUE10. Some accessories, replacement parts, or services may still be available.
SR50A-L Sonic Distance Sensor
Services Available
Repair Yes
Free Support Yes

The next generation of the SR50A snow-depth sensor is now available.

Check out the SnowVUE™10.

Overview

The SR50A Sonic Distance Sensor provides a non-contact method for determining snow 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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Technical Description

The SR50A was designed to meet the stringent requirements of measuring snow depth, and it uses a multiple echo processing algorithm to help ensure measurement reliability.

SDI-12, RS-232, and RS-485 output options are available for measuring the SR50A. Campbell Scientific’s MD485 interface can be used to connect one or more SR50A sensors in RS-485 mode to an RS-232 device. This can be useful for sensors that require lead lengths that exceed the limits of either RS-232 or SDI-12 communications.

The SR50A replaced the SR50 in March 2007. The newer SR50A is smaller and has different output options than its predecessor. The SR50AH is available with a heater option for locations where rime ice is a problem.

Specifications

Measurement Description Snow depth
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
Temperature Accuracy
  • ±0.2° (at 0° to 50°C)
  • ±0.75° (at -45° to 0°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.

Dataloggers

Product 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
CR211X (retired) SDI-12
CR216X (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.
CR300 SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR3000 (retired) 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.
CR350 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 (retired) SDI-12 and RS-232. For RS-485, requires an MD485 interface or similar RS-485 to RS-232 interface.
CR850 (retired) 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.

Miscellaneous

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

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.

Related FAQs

Number of FAQs related to SR50A-L: 16

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  1. 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.

  2. Can an SR50A-L be connected to a datalogger on an SDI-12 port?

    Yes. This sensor has an SDI-12 output.

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

    No.

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

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

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

    No.

  6. If an SR50A-L is used to measure snow depth at a site that has wind, rain, and extreme changes in temperature, which results in condensation, what can be done to ensure the sensor operates properly?

    The SR50A-L must be vented to the atmosphere to operate correctly. This is normally not a problem in alpine conditions, but in temperate, damp climates, the vent may introduce condensation that will ultimately disable the sensor. To combat this, a small package of desiccant is placed inside the sensor head, which will keep the interior dry under most conditions. If especially wet or condensing conditions are expected, the desiccant should be changed frequently to prevent moisture accumulation. Campbell Scientific offers a desiccant ½ unit bag (pn 905) and a 0.75 g desiccant bag (pn 4091).

  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. Can an SR50A-L be hardwired to a datalogger that is 2,000 ft away with no direct line of sight?

    No. The maximum cable length is approximately 800 ft.

  9. 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.

  10. 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.

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