CS650 - volume soil moisture sensor

Sensor of volumetric soil moisture, soil temperature, conductivity and soil permittivity.

The digital output SDI-12 can be directly connected (without the need for another converter) to units H3, H7, H40, H50, STELA or M4016.


CS650 - sonda objemové půdní vlhkosti

Basic description

The CS650 consists of two 30 cm long stainless steel rods connected to an electronics board. The CS650 sensors with a large sensing volume (> 6 L) are suitable for soils with low to medium electrical conductivity.

The CS650 measures propagation time, signal attenuation and temperature. From these crude values, the dielectric permittivity, volume water content and volume electrical conductivity are then derived.

The measured signal attenuation is used to correct the effect of loss on reflection detection and thus to measure the propagation time. This loss effect correction allows accurate measurement of water content in soils with a volume EC ≤3 dS m-1 without performing a specific soil calibration.

The volumetric electrical conductivity of the soil is also calculated from the attenuation measurement. A thermistor in thermal contact with a probe near the epoxy surface measures the temperature. The horizontal installation of the sensor ensures accurate measurement of the soil temperature at the same depth as the water content. Temperature measurement in sensor orientations other than horizontal will sense the temperature near the inlet of the rods to the sensor body.

Technical parameters

Performed measurements: Electrical conductivity of soil (EC), relative dielectric permittivity, volume content of water (VWC), soil temperature

Sensed soil volume: 3600 cm3 (radius ~ 7.5 cm around each probe electrode and 4.5 cm behind the end of the electrode)

Operating temperature range: -50 °C to + 70 °C

Output signal: SDI-12

Rise time: 3 s

Measurement time: 3 ms for measurement; 600 ms to complete the SDI-12 command

Maximum possible cable length: 500 m - up to 25 sensors can be connected to one cable

Mechanical dimensions:

Rod electrode spacing: 32 mm

Degree of protection: IP68

Rod electrode diameter: 3.2 mm

Rod electrode length: 300 mm

Probe body dimensions: 85 x 63 x 18 mm

Probe weight: 310 g

Supply voltage and current consumption

Power voltage: 6 až 18 VDC

Current consumption during measurement (3 ms):

  45 mA typicky (@ 12 VDC)

  80 mA (@ 6 VDC)

  35 mA (@ 18 VDC)

Standby current consumption: 135 μA typicky (@ 12 Vdc)


Electric conductivity

Range for soils EC 0 až 3 dS / m

Accuracy: ± (5% odečtu + 0,05 dS / m)

Relative dielectric permittivity

Range: 1 to 81


± (2% of the reading + 0,6) from 1 to 40 for soils EC ≤ 3 dS / m

± 1,4 (from 40 to 81 for soils EC ≤ 1 dS / m)

Volumetric water content

Range: 0 to 100% (with command M4)

Accuracy of water content:

± 1% (with soil-specific calibration)

± 3% pro EC <3 dS / m

Soil temperature

Range: -50 ° až + 70 °C

Distinction: 0,001 °C


± 0,1 °C (for typical soil temperatures [0 to 40 °C], probe body stored in soil)

± 0,5 °C (for full temperature range)


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