Design considerations and calibration of stress transducers for soil

Strain gage pressure transducers are most frequently used for soil stress state determinations. Their construction, rugged and mechanically resistant, enables them to measure stresses within a wide range (up to 500 kPa) in harsh conditions. Output signals are easily readable and stable. The accuracy of the measurements, however, depends upon proper design and calibration before use in soil. This paper contains information on design considerations and results from calibration tests of transducers of two membrane diameters: 20 and 30 mm. The calibration test stand, as well as calibration procedures, are described in detail. For calibration tests, natural soils were used, as well as steel balls, to simulate the effect of the aggregated structures of arable soils and grain materials. The calibration method considered different soil types as well as soil water content. Soil and its water content were found to have an effect on output scale factor.