CS725 Snow Water Equivalent Sensor
Rugged, Reliable
Passive no-contact detector, ideal replacement for snow pillow
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications

Overview

The CS725 measures snow-water equivalent (SWE) by passively detecting the change in naturally occurring electromagnetic energy from the ground after it passes through snow cover. It is mounted above the ground and has no contact with the snow. As the snow pack increases, the sensor detects the attenuation of the electromagnetic energy from the ground, and SWE can be calculated. The measurement area of the CS725 is 50 to 100 square meters (540 to 1,075 square feet), making it an excellent replacement sensor for the traditional snow pillow and snow scale.

Common applications for the CS725:

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Benefits and Features

  • Non-contact measurement
  • Excellent replacement for traditional snow-pillow sensors
  • Does not cause the melt of light snow
  • Greatly reduces the need for site visits
  • No site preparation or earthworks required for set-up
  • Performance not affected by rainfall or snowfall
  • Effective with any type of snow or ice
  • Will not cause snow drifting
  • Seven-year maintenance cycle
  • No antifreeze chemicals used (i.e. glycol)

The CS725CBL-L Cable is required to use the CS725.

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Detailed Description

The CS725 uses an innovative, non-contact method of measuring snow water equivalent (SWE). It passively detects the change in naturally occurring electromagnetic energy (mainly from the decay of 40K) from the ground after it passes through snow cover.

As SWE changes, the amount of energy that penetrates the snow pack changes—regardless of what state of the water (that is, liquid or frozen). A sensor installed above the ground prior to the first snowfall will have a base-line measurement of the electromagnetic energy coming from the ground. As snow accumulates and energy is attenuated, the SWE value will increase. The CS725 has an internal processor that determines the SWE and sends this information to a datalogger or communication device via RS-232.

Specifications

Measurement Range 600 mm maximum water equivalent
Accuracy
  • ±15 mm (from 0 to 300 mm)
  • ±15% (from 300 to 600 mm)
Resolution 1 mm
Coverage Angle 60°
Operating Temperature Range -40° to +40°C
Power Requirements 11 to 15 Vdc
Power Consumption 180 mA
Output Format RS-232 (1200 to 115200 bps)
Cable Type Four conductor, two-twisted pair, 22 AWG, Santoprene jacket
Maximum Cable Length 30 m (98.43 ft)
Diameter 12.7 cm (5 in.)
Length 62 cm (24.4 in.)
Main Body Weight 9 kg (20 lb)
Collimator Weight 25 kg (55 lb)
Total Weight 34 kg (75 lb)

Compatibility

Datalogger Considerations

Compatible Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR5000 CR7X CR9000X CR6 Series

Collimator Considerations

Other sources of electromagnetic radiation (40K) such as trees, vegetation, and buildings that are not covered by the same amount of snow as the ground can affect the readings. To filter these signals, the optional heavy steel collar (collimator assembly, pn 29390) is installed on the bottom of the CS725.

The following chart outlines when a collimator should be used:

Site Characteristics Maximum SWE 300 mm Maximum SWE 300 to 400 mm Maximum SWE > 400 mm

Very open site with no proximity to trees, buildings, or tall vegetation within a 48 m (160 ft) radius

Optional

Optional

Optional

No trees, buildings, or tall vegetation within a 24 m (80 ft) radius

Optional

Optional

Required

No trees, buildings, or tall vegetation within a 12 m (40 ft) radius

Optional

Required

Required

Site with minimum clearance radius of 6 m (20 ft) radius

Required

Required

Required

Note: Always confirm that your sensor has the “Collimator Installed” parameter set properly. The SWE calculations are different for a sensor with and without a collimator.


Frequently Asked Questions

Number of FAQs related to CS725: 5

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  1. Yes, however the data would have to be back-calculated at the end of the season once all snow has melted, you would not have real-time SWE measurements.

  2. The CS725 should be installed prior first snow fall to establish a good baseline reading. However, it can be installed after and the data back-calculated at the end of season. The only problem with this is you won’t have accurate SWE values during the season.
  3. The sensor takes the measurement and outputs data in RS-232 format.  If your datalogger can receive RS-232 signals, it should work with the CS725.  It’s also best that the datalogger can measure volumetric soil moisture.

  4. No, it only measures naturally emitted gamma radiation coming from the ground.  The strongest signal of gamma comes from potassium-40 (40K). 

  5. No, at this time the sensor does not output in SDI-12 format; however, it may be added in the future.

Case Studies

Northern Canada: Hydro-electric Power Forecasting
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Italy: CS725 SWE Sensor Field Test
System integrator Hortus Srl installed a Campbell Scientific CS725 SWE sensor (Snow Water Equivalent) in......read more