Overview

The SR50A is a rugged acoustic sensor for measuring the distance from the sensor to a target. It is typically used to measure snow or water depth, but it is well-suited for other uses.

Because the speed of sound in air varies with temperature, an independent temperature measurement is required to compensate the distance reading. A simple calculation is applied to initial readings for this purpose.

Note: Campbell Scientific recommends model SR50A-316SS-L for marine environments.

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Benefits and Features

  • Wide operating temperature range
  • User-selectable options for output
  • Compatible with most Campbell Scientific dataloggers
  • Optional heater available (3W @ 12VDC or 12VAC)

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

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Detailed Description

The SR50A was designed to meet the stringent requirements of measuring depths and 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

General

Measurement Time < 1.0 s
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 datalogger’s 12 Vdc power supply)
Measurement Range 0.5 to 10 m (1.6 to 32.8 ft)
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

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

Compatibility

Datalogger Considerations

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

Compatible Contemporary Dataloggers (SDI-12)

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X CR300 Series CR6

Compatible Retired Dataloggers (SDI-12)

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X

Compatible Contemporary Dataloggers (RS-232)

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X CR300 Series CR6

Compatible Retired Dataloggers (RS-232)

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X

Compatible Contemporary Dataloggers (RS-485)

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X CR300 Series CR6
* * * * *

Compatible Retired Dataloggers (RS-485)

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X
*

*Requires an MD485 interface or similar RS-485 to RS-232 interface.

Downloads

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

Current SR50A / AT firmware. View Update History

Frequently Asked Questions

Number of FAQs related to SR50A-L: 17

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

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

  3. 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.

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

  5. 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.

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