Polarization Mechanism Analysis and Equivalent Model of Green Sand under Direct Current Electric Field.

Aiming at the polarization phenomenon when the moisture content of green sand is measured by the resistance method, the polarization mechanism of green sand under the direct current electric field is further analyzed. The results show that the current through the sand specimen can be divided into the through-type conduction current and the absorption current, and the former keeps invariable while the latter decreases exponentially with the time. It is the absorption current that causes the polarization of green sand. Further, the equivalent model can be obtained where the serial connection of a resistor R and a capacitor C is in parallel with another resistor R'. To weaken or eliminate the polarization effect, three measures can be taken from decelerating the electron movement speed, accelerating the electrode reaction speed and eliminating the charge accumulation on the electrodes. So the small exciting voltage, the large electrode area and the appropriate frequency are helpful to reduce the polarization. [ABSTRACT FROM AUTHOR]