Time-Domain Reflectometry is a proven technique for measuring volumetric water content. The CS616 and CS625 sensors allow data logger users to monitor soil moisture using TDR-based principles without the costly cable testing equipment that is generally used in research applications.
The probes consist of an epoxy-coated circuit board that is connected to two, 30cm stainless steel rods. When activated, the circuit board generates an electrical output which is transmitted along the rods. The time taken for the transmission and subsequent reflection of this signal is based on the dielectric permittivity of the material in contact with the rods. In the case of soil, this is governed predominantly by water content.
The sensor output is connected to one of the data logger’s single ended analog inputs by the four-conductor cable. The data logger program is used to convert the probe’s analog (square wave) output into a volumetric water content measurement.
The CS616 probes are suitable for use with our CR800 series, CR1000, CR3000 & CR5000 data loggers, while the CS625 has been specifically designed to work with our smallest data logger, the CR200 series.