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SR50A-L Sonic Distance Sensor
Services Available
Repair Yes
Free Support Yes

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

The "-L" on a product model indicates that the cable length is specified at the time of order.

Images

SR50A-L with cable
SR50A-L with cable
SR50A-L with cable
Image shown is an SR50A-316SS-L mounted to a 19517 SR50A Mounting Kit (sold separately).<br />The SR50A and the SR50A-316SS use the same chassis design.
SR50A-L mounted to a 19517<br />SR50A Mounting Kit and crossarm<br />(sold separately)
SR50A-L mounted to a<br />19484 SR50A Mounting Stem<br />(sold separately)
SR50A-L mounted to a crossarm using 19484 SR50A Mounting Stem and 17953 1 x 1 inch Nu-Rail crossover fitting (sold separately)

Detailed 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

Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.

Data Loggers

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
CR206X (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.
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 (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 Update History

Frequently Asked Questions

Number of FAQs related to SR50A-L: 15

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

    No.

  2. 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.

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

    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 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. 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.

  7. Does the SR50A-L need a temperature probe?

    Because the speed of sound changes with temperature, Campbell Scientific recommends using the SR50A-L in tandem with a temperature sensor for the most accurate measurements.

  8. How can snow depth less than 0.5 m be measured using an SR50A-L?

    Position the sensor at a height that is between 0.5 m and 10 m above the target.

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

    No. The maximum cable length is approximately 800 ft.

  10. 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.

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