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CS625 Water Content Reflectometer for CR200(X)-Series
Services Available
Repair Yes
Calibration Yes
Free Support Yes

Overview

The CS625 measures the volumetric water content from 0% to saturation. It is similar to our CS616 but is designed specifically for CR200- and CR200X-series dataloggers. This reflectometer has a 0 to 3.3 V square wave frequency output that our CR200(X)-series dataloggers can measure.

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Benefits and Features

  • High accuracy and high precision
  • Fast response time
  • Designed for long-term unattended water content monitoring
  • Probe rods can be inserted from the surface or buried at any orientation to the surface.

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Detailed Description

The CS625 consists of two 30-cm-long stainless steel rods connected to a printed circuit board. The circuit board is encapsulated in epoxy, and a shielded four-conductor cable is connected to the circuit board to supply power, enable probe, and monitor the output.

The CS625 measures the volumetric water content of porous media (such as soil) using the time-domain  measurement method; a reflectometer (cable tester) such as the TDR100 is not required. This method consists of the CS625 generating an electromagnetic pulse. The elapsed travel time and pulse reflection are then measured and used to calculate soil volumetric water content.

Response Characteristics

The signal propagating along the parallel rods of the CS625 is attenuated by free ions in the soil solution and conductive constituents of the soil mineral fraction. In most applications, the attenuation is not enough to affect the CS625 response to changing water content, and the response is well described by the standard calibration. However, in soil with relatively high soil electrical conductivity levels, compacted soils, or soils with high clay content, the calibration should be adjusted for the specific medium. Guidance for making these adjustments is provided in the operating manual.

Specifications

Operating Temperature Range 0° to 70°C
Probe-to-Probe Variability ±0.5% VWC in dry soil, ±1.5% VWC in typical saturated soil
Precision 0.1% VWC
Resolution 0.1% VWC
Output 0 to 3.3 V square wave (with frequency dependent on water content)
Current Drain 65 mA @ 12 Vdc (when enabled)
Power Supply Voltage 5 Vdc minimum; 18 Vdc maximum
Enable Voltage 4 Vdc minimum; 18 Vdc maximum
Electromagnetic CE compliant (Meets EN61326 requirements for protection against electrostatic discharge.)
Rod Spacing 32 mm (1.3 in.)
Rod Diameter 3.2 mm (0.13 in.)
Rod Length 300 mm (11.8 in.)
Probe Head Dimensions 85 x 63 x 18 mm (3.3 x 2.5 x 0.7 in.)
Cable Weight 35 g per m (0.38 oz per ft)
Weight 280 g (9.9 oz) without cable

Compatibility

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

Dataloggers

Product Compatible Note
CR1000 (retired)
CR200X (retired)
CR206X (retired)
CR211X (retired)
CR216X (retired)
CR295X (retired)
CR300
CR3000
CR310
CR5000 (retired)
CR800
CR850
CR9000X (retired)

Additional Compatibility Information

RF Considerations

The RF emissions are below FCC and EU limits as specified in EN61326 if the CS625 is enabled less than 0.6 ms, and measurements are made less frequently than once a second. External RF sources can also affect the CS625 operation. Consequently, the CS625 should be located away from significant sources of RF such as ac power lines and motors.

Installation Tool

The CS650G makes inserting soil-water sensors easier in dense or rocky soils. This tool can be hammered into the soil with force that might damage the sensor if the CS650G were not used. It makes pilot holes into which the rods of the sensors can then be inserted. It replaces both the 14383 and 14384.

Data Logger Considerations

Each CS625 requires a single-ended input channel. A control port is used to enable one or more probes.

Note: A maximum of four CS625 probes can be measured by one CR200(X) datalogger. Valid channel options are analog channels 1 through 4.


Frequently Asked Questions

Number of FAQs related to CS625: 34

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  1. Yes, as long as the data logger can detect a 0 to 3300 mV square wave over a frequency range of 29 to 67 kHz.

  2. Yes. The rugged design of the CS616/CS625 protects the probe electronics from water under these conditions. Many CS616/CS625 reflectometers have been working reliably in very wet conditions for more than ten years.

  3. The sensitive volume of the CS616/CS625 varies with water content. A general guideline is that the sensitive volume is within approximately a 32 mm radius from each rod.

  4. If a soil-specific calibration is performed, the CS616/CS625 may be used in soil with a maximum bulk electrical conductivity of 5 dS/m.

  5. The period value is corrected to the temperature at which the water content calibration was performed, and then the water content equation is applied to the corrected period. Temperature correction is soil specific because the effect that temperature has on the period value varies with soil texture and electrical conductivity. A temperature correction equation that was developed for a sandy loam soil with low bulk electrical conductivity is provided in the CS616 and CS625 instruction manual.

  6. Some customers have tried to use the CS616 or CS625 to measure the moisture content within a tree, but the calibration proved to be problematic. Campbell Scientific cannot provide any specific guidance for this application.

  7. The CS616/CS625 can measure volumetric water content over the entire range from completely dry to saturation. A soil-specific calibration will improve accuracy, especially in very dry soil.

  8. If the new site has soil with a different soil type, a soil-specific calibration may be needed. For soil that is sandy or sandy loam with low bulk electrical conductivity, the calibration equation in the CS616 and CS625 instruction manual works well. 

  9. The CS616 and CS625 are water-content reflectometers with measurement electronics built into the probe head. The electronics generate a signal, which is sent directly to the data logger. The CS610-L, and other three-rod probes sold by Campbell Scientific, are TDR probes that have no electronic components and serve as wave guides for a time-domain reflectometer such as the TDR100.