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.

Images

SR50A-L with cable

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

  4. 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.

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

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