Primary measuring transducer of moisture content for grain quality control

Abstract

The main task of the research is the development of the primary capacitive measuring transducer that can perform testing influences on the material under research, applied for automatic “type uncertainty” method error compensation, that takes place because of the method of measurement imperfection. To estimate the relevant level of testing influences a group of different materials with 2, 2.5, 3 and 3.5 dielectric permittivity values was taken for 0, 10, 20, 30 and 40% of moisture content control points. The primary measuring transducer of moisture content is organized with an electrode system in a form of V-type plates, which is fixed on the internal surface of two dielectric rings. Testing influences on the substance are reproduced directly in the capacitive primary transducer by simple metallic plates with fixed thickness introduction into the space between separate electrodes of an electrode system. A prototype product of the primary measuring transducer had been experimentally tested together with the new method of moisture measurement, which includes two additive, two multiplicative and two complementary testing influences on the material under research. Moisture content with nominal values 0, 10, 20 and 30% was reproduced by certain group of grains with different dielectric permittivity values. Experimental setup of an adaptive moisture meter was assembled using the substitution method of measurement to provide good accuracy for the conditions of capacitance measurement in substances with significant dielectric losses. The accuracy of moisture measurement was defined as discrepancy between average measured and nominal moisture content and as an uncertainty of this discrepancy in a form of type A uncertainty.