An Economical, Digital Meter for Gypsum Soil Moisture Blocks

Most meters for soil moisture blocks are designed for use with relatively moist soils. This paper describes a meter that utilizes a frequency output proportional to block resistance and that is usable over a relatively wide range of soil moisture. Advantages of this meter are digital display, easy and reliable operation, low power drain, and simple economical design. It is stable with changes in temperature, lead length to sensors, and battery voltage. The meter functions satisfactorily with several types of commercially available gypsum blocks and provides good resolution of matric water potential in the range of −0.06 to −1.5 MPa.