The CS616 measures the volumetric water content (VWC) of porous media (such as soil) from 0% to saturation. The probe outputs a megahertz oscillation frequency, which is scaled down and easily read by a Campbell Scientific data logger.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 the probe, and monitor the output.
The CS616 uses the time-domain measurement method to measure VWC; a reflectometer (cable tester) such as the TDR200 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 instruction manual.
|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).|
|Operational Temperature||0° to +70°C|
|Probe-to-Probe Variability||±0.5% VWC in dry soil, ±1.5% VWC in typical saturated soil|
|Precision||Better than 0.1% VWC|
|Output||±0.7 V square wave (with frequency dependent on water content)|
|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|
Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.
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 was 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 data logger’s single-ended analog inputs. A data logger control port is typically used to enable the CS616 for the amount of time required to make the measurement. Data logger 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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The CS616 has a faster period output than the CS615-L, so it does not work with the 21X dataloggers.
No. The output is too fast to be measured on the pulse channel of a 21X or CR7.
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.
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.
Yes, but the CS616/CS625 will need a soil-specific calibration. The high organic matter content of peat will likely cause the CS616/CS625 period to be out of bounds for use with the CS616() CRBasic instruction and P138 Edlog instruction. In that situation, the CRBasic PeriodAvg() instructionor the Edlog P27 Period Average instruction may be used as described in the CS616 and CS625 instruction manual.
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.
Running the cable through electrical conduit or PVC pipe will protect the cable from rodents. A trench 30 to 60 cm deep will protect it from most other human or animal activity. Some customers have found that extra cable can be coiled and left inside a box, such as an irrigation valve box or something similar. When using a box, seal any holes that are large enough for rodents to enter. When cables are exposed on the ground surface, some customers have found that wrapping the cables in the metal screening used for screen doors discourages animals from chewing on them.
Fine roots do not significantly affect the CS616/CS625 reading.
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.
Yes. For program examples and guidance on using a multiplexer with one of these reflectometers, see the CS616 and CS625 instruction manual.