The CS616 measures the volumetric water content from 0% to saturation. The probe outputs a megahertz oscillation frequency, which is scaled down and easily read by a Campbell Scientific datalogger.Read More
The CS616 is comprised of two 30-cm-long stainless steel rods connected to the measurement electronics. 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 CS616 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 CS616 generating an electromagnetic pulse. The elapsed travel time and pulse reflection are then measured and used to calculate soil volumetric water content.
The signal propagating along the parallel rods of the CS616 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 CS616 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.
|Operational Temperature||0° to +70°C|
|Probe-to-Probe Variability||±0.5% VWC in dry soil, ±1.5% VWC in typical saturated soil|
|Accuracy||±2.5% VWC (using standard calibration with bulk electrical conductivity of ≤ 0.5 dS m-1, bulk density of ≤ 1.55 g cm-3, and measurement range of 0% to 50% VWC)|
|Precision||Better than 0.1% VWC|
|Output||±0.7 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|
The RF emissions are below FCC and EU limits as specified in EN61326 if the CS616 is enabled less than 0.6 ms, and measurements are made less frequently than once a second. External RF sources can also affect the CS616 operation. Consequently, the CS616 should be located away from significant sources of RF such as ac power lines and motors.
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.
The reflectometer connects directly to one of the datalogger’s single-ended analog inputs. A datalogger control port is typically used to enable the CS616 for the amount of time required to make the measurement. Datalogger instructions convert the probe square-wave output to period which is converted to volumetric water content using a calibration.
Number of FAQs related to CS616: 36
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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.
Yes, as long as the datalogger can detect a ±700 mV square wave over a frequency range of 29 to 67 kHz.
No. The output is too fast to be measured on the pulse channel of a 21X or CR7.
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.
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 datalogger. 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.
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.
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.
Fine roots do not significantly affect the CS616/CS625 reading.
Yes. For program examples and guidance on using a multiplexer with one of these reflectometers, see the CS616 and CS625 instruction manual.