Abstract
This paper describes a cylindrical grid electrode designed for use in the capacitance or resistance method of measuring the electrical properties which are characteristic to the sample materials of powder and grain.
The cylindrical grid electrode is three cylindrical electrodes on a low loss insulator tube. The sample material of powder (or of grain) is placed in the cylindrical space surrounded by the insulator tube.
The characteristics of this electrode are measured by the capacitance change method and were discussed with the equivalent circuit. From the result, four detecting methods were found for measuring the electrical properties of powder and grain by this electrode, and the conditions for obtaining the maximum sensitivity with these methods were clearly stated.
Experimental results have shown that the moisture measuring method due to the capacitance measurement by this electrode for granulated sugar is difficult on account of the constancy of the capacitance within the necessary humidity range. Therefore, it became evident that the detection of a small moisture content in powder and grain must be done by measuring the high resistance.
The cylindrical grid electrode permits accurate non-contact measurements using a small volume of specimen and was found to give consistent results with a small variance, independently of particle orientations in the insulator tube.
