High Accuracy and Precision
Designed for long-term monitoring
Documents WEATHER Documents WATER Documents ENERGY Documents MACHINES Documents STRUCTURES Documents EARTH

Overview

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

Benefits and Features

  • Compatible with most Campbell Scientific dataloggers
  • 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 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.

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 operating manual.

Specifications

General

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
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

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 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

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.

Compatible Contemporary Datalogger

CR200(X) Series CR800/CR850 CR1000 CR3000 CR6 CR9000X

Compatible Retired Dataloggers

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X

Frequently Asked Questions

Number of FAQs related to CS616: 36

Expand AllCollapse All

    • 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.
  1. 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.

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

  3. 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.

  4. 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.

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

  6. 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. 

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

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

Case Studies

Korea: Damage from Freezing Roads
Korea Expressway Corporation (KEC) was established in 1969 to construct and manage expressways throughout South Korea. KEC’s goal has been......read more
Delaware: Environmental Observing System
The Delaware Environmental Observing System (DEOS) is a real-time system dedicated to monitoring environmental conditions across the State of Delaware,......read more
West Texas Mesonet
The West Texas Mesonet (WTM) project was initiated by Texas Tech University in 1999 to provide free real-time weather and......read more