The soil moisture sensor SMS009 is a gypsum block sensor measuring soil tension rather than water content. This way the sensor simulates the plants access to the available water in the soil. Soil moisture tension is a measure of the energy a plant must apply to the soil in order to extract the available moisture. The unit of measure is kPa (kilo pascals). The higher the measure, the harder the plant must work to extract the moisture. To avoid polarisation the SMS009 is excited by ac sinusoidal ac voltage. A verity of APCS modules can be built for SMS009 input

Typical Applications

• Watering on/off control using LLD206

• Soil moisture profile monitoring and control using USC701 and CDT228