Design and performance of psychrometric soil water potential meter

The paper presents the design and performance of an eight-channel thermocouple psychrometer working in psychrometric mode. The availability of advanced electronic components of high accuracy and microcontroller supervision enables to build a simple, reliable and not expensive device for use in the range water potential from −6 up to −0.2 MPa and possibly higher. The operation of the meter is computer controlled, the input voltage is sampled with the 50 Hz frequency and ±50 nV resolution. The calibration procedure of the psychrometric sensors available from vendors is presented, too. The meter and the probes can be easily adapted to automatic soil status monitoring stations and also to determine properties of materials used in building and food industries in the relative humidity range of 95-99.99%.