253-L

The 253 determines soil water potential by measuring electrical resistance. When the 253 is wet, electrical resistance is low. As the 253 dries, resistance increases.

The 253 consists of two concentric electrodes embedded in a reference matrix material. The matrix material is surrounded by a synthetic membrane for protection against deterioration. An internal gypsum tablet buffers against the salinity levels found in irrigated soils.

The 253's construction can allow the sensor (in some circumstances) to be left in the soil all year, eliminating the need to remove the sensor during fallow periods.

The 253 connects to a datalogger via an AM16/32-series multiplexer. Because the multiplexer contacts close only during measurement, electrical currents leading to premature degradation of the 253 are eliminated.