CS625 Water Content Reflectometer for CR200(X)-Series and CR300-Series
High Accuracy and Precision
Designed for long-term monitoring
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications

Overview

The CS625 measures the volumetric water content from 0% to saturation. It is similar to our CS616 but is designed specifically for CR200(X) and CR300-series dataloggers. This reflectometer has a 0 to 3.3 V square wave frequency output that our CR300-series and 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

Measurements Made Volumetric water content of porous media (such as soil)
Water Content Accuracy ±2.5% VWC (using standard calibration with bulk EC of ≤ 0.5 dS m-1, bulk density of ≤ 1.55 g cm-3, and measurement range of 0% to 50% VWC)
Required Equipment Measurement system
Soil Suitability Long rods and lower frequency are well-suited for soft soil with low electrical conductivity (< 2 dS/m).
Rods Not replaceable
Sensors Not interchangeable
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)
  • 45 μA (quiescent typical)
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

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.

Datalogger 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.

Compatible Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR5000 CR7X CR9000X CR300 Series

Frequently Asked Questions

Number of FAQs related to CS625: 34

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

  2. No. The output is too fast to be measured on the pulse channel of a 21X or CR7.

    • The CS616/CS625 is not receiving power. Ensure that the red wire is well connected to 12V and that the black and clear wires are both connected to G. Also check that the orange wire is well connected to a control port and that the datalogger program references that control port as part of the sensor measurement.
    • The datalogger is not receiving a signal from the CS616/CS625. Ensure that the green wire is well connected to a single-ended analog input channel and that the datalogger program references that channel in the CS616() or PeriodAvg() instruction.
    • The soil is too conductive. If the soil has high electrical conductivity, high clay content, or high organic matter content and the CRBasic instruction CS616() or Edlog instruction P138 is used, the period might be out of range for that instruction. In that situation, it may be possible to use PeriodAvg() or P27 as shown in the program examples of the CS616 and CS625 instruction manual.
  3. The CS616/CS625 will survive frozen soil conditions, but the principle behind using bulk soil dielectric permittivity to estimate water content requires that the water be in liquid form. When soil water freezes, its dielectric drops from approximately 80 to 4, making it indistinguishable from soil solids. Consequently, the CS616/CS625 is not able to measure the water content of frozen soil.

  4. Yes. The PeriodAvg() CRBasic instruction may be used to measure the CS625 on a CR1000, CR800-series, or CR3000 datalogger. To make this work, it is important that the Threshold parameter be set to 1650 mV as shown in the following example:

        PortSet (1 ,1 ) ‘Enable CS625 by setting C1 high (orange wire to C1)

        PeriodAvg (PA_uS,1,mV250,1,1650,0,100,10,1.0,0) ‘Read Period on SE1 (green wire to SE1)

        PortSet (1 ,0) ‘Disable CS625 by setting C1 low

  5. If the electrical conductivity within the waste is less than 5 dS/m and there is good contact between the probe rods and the waste, the CS616/CS625 should respond predictably to changes in water content. The heterogeneous nature and changing bulk density of solid waste, however, make calibration difficult.

  6. 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.

  7. Fine roots do not significantly affect the CS616/CS625 reading.

  8. Yes. For program examples and guidance on using a multiplexer with one of these reflectometers, see the CS616 and CS625 instruction manual.