CS616 and CS625 Water Content Reflectometers
6
6.3
Electrical Specifications
Output
CS616:
0.7 volt square wave with frequency
dependent on water content
CS625:
0 to 3.3 volt square wave with frequency
dependent on water content
Power:
65 mA @ 12 Vdc when enabled, 45
A
quiescent
Power Supply Requirements:
5 Vdc minimum, 18 Vdc maximum
Enable Voltage:
4 Vdc minimum, 18 Vdc maximum
Maximum Cable Length:
305 m (1000 ft)
Electromagnetic
Compatibility:
The CS616/CS625 is Πcompliant with
performance criteria available upon
request. RF emissions are below EN55022
limits if the CS616/CS625 is enabled less
than 0.6 ms and measurements are made at
a 1 Hz (1 per second) or slower frequency.
The CS616/CS625 meets EN61326
requirements for protection against
electrostatic discharge and surge.
6.4
Operational Details
The
accuracy
specification for the volumetric water content measurement
using the CS616/CS625 probes is based on laboratory measurements in a
variety of soils and over the water content range air dry to saturated. The
soils were typically sandy loam and coarser. Silt and clay were present in
some of the soils used to characterize accuracy.
Resolution
is the minimum change in the dielectric permittivity that can
reliably be detected by the water content reflectometer. The CS616 or
CS625 is typically used to measure soil volumetric water content.
Precision
describes the repeatability of a measurement. It is determined
for the CS616 and CS625 by taking repeated measurements in the same
material. The precision of the CS616/CS625 is better than 0.1 %
volumetric water content.
Soil Properties
The water content reflectometer operation can be affected when the signal
applied to the probe rods is attenuated. The probe will provide a well-
behaved response to changing water content, even in attenuating soils or
other media, but the response may be different than described by the
standard calibration. Consequently, a unique calibration is required.
Change in probe response can occur when soil bulk electrical conductivity
is greater than 0.5 dS m
–1
. The major contributor to soil electrical
conductivity is the presence of free ions in solution from dissolution of soil
salts. Soil organic matter and some clays can also attenuate the signal.
