CS616 30 cm Water Content Reflectometer
High Accuracy and Precision
Designed for long-term monitoring
weather applications supported water applications supported energy applications supported gas flux and turbulence applications supported infrastructure applications supported soil applications supported

Overview

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

Benefits and Features

  • Compatible with most Campbell Scientific data loggers
  • High accuracy and high precision
  • Fast response time
  • Designed for long-term unattended water content monitoring
  • Compatible with AM16/32-series multiplexers, allowing measurement of multiple sensors
  • Probe rods can be inserted from the surface or buried at any orientation to the surface.

Images


Detailed Description

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.

Response Characteristics

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.

Specifications

Measurements Made Volumetric water content (VWC) of porous media (such as soil)
Measurement Range 0% to saturation
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 Better than 0.1% VWC
Resolution 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

Compatibility

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.

Data Loggers

Compatible Note
CR1000 (retired)
CR1000X
CR300
CR3000 (retired)
CR310
CR350
CR6
CR800 (retired)
CR850 (retired)

Additional Compatibility Information

RF Considerations

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.

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 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.

Data Logger Considerations

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.

FAQs for

Number of FAQs related to CS616: 36

Expand AllCollapse All

  1. The CS616 has a faster period output than the CS615-L, so it does not work with the 21X dataloggers.

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

  3. 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.

  4. 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.

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

  6. 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.

  7. Yes, as long as the data logger can detect a ±700 mV square wave over a frequency range of 29 to 67 kHz.

  8. Yes. The dielectric permittivity of water varies with temperature, which will cause the CS616/CS625 period to decrease with increasing temperature and increase with decreasing temperature. In addition, the electrical conductivity of the soil water solution is temperature dependent, causing the CS616/CS625 period to increase with increasing temperature and decrease with decreasing temperature. The net effect of those two opposing forces depends on the soil texture and electrical conductivity. The temperature correction equation in the CS616 and CS625 instruction manual was developed using a sandy loam soil with relatively low electrical conductivity. For soils with finer texture or higher electrical conductivity, Campbell Scientific recommends a soil-specific temperature correction equation.

  9. 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. 

  10. 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.