Soil water matric potential sensors are essential for understanding agricultural and natural ecosystems. However, accurate sensors that can be used for a wide range of soil moisture conditions have yet to be developed. The MPS-1 sensor by Decagon Devices, Inc. was tested and calibrated in a laboratory setting using pressure plate and suction apparatuses. This study evaluated the general performance of the MPS-1 sensor by: (1) testing for a wide range of varying soil conditions, including temperature and hysteresis, (2) determining measurement range, sensitivity, consistency, accuracy, and variation among sensors, and (3) developing a laboratory calibration procedure prior to field installation. Sensitivity of the MPS-1 sensor was found to be a highly nonlinear function of soil matric potential. Sensor-to-sensor variations were large, but were partly removed using the presented one-point calibration. Variation among sensors is largely eliminated by using a sensor-specific calibration. The MPS-1 sensitivity to temperature was relatively small and inconsistent, and hysteresis effects were relatively minor. Individual sensor output readings were consistent in time, remaining almost constant over a measurement period of 1.5 years. By comparing calibrated MPS-1 sensors with tensiometers in the field, we conclude that measurement uncertainty is less than 10 kPa (or 0.1 bar) in the range from 10 to 60 kPa.
Malazian, A., Hartsough, P.C., Kamai, T., Campbell, C.S., Cobos, D.R. and Hopmans, J.W. (2011): Evaluation of MPS-1 soil water potential sensor. J. of Hydrology. 402:126-134.. DOI: 10.1016/j.jhydrol.2011.03.006
This Paper/Book acknowledges NSF CZO grant support.