ELIMINATION OF THE ANOMALOUS HUMIDITY EFFECT IN PRECISION CAPACITANCE BASED TRANSDUCERS

An anomalous humidity effect has been observed in a precision capacitor-based displacement transducer. This effect displays a threshold, well below the dew point, above which the capacitance change exceeds by far the increase in moisture-caused dielectric constant of the air dielectric. This effect, common to air capacitors in general, results from water vapor adsorption on insulator surfaces. It can be eliminated by shielding the capacitor in a way which removes the humidity sensitive flux from the internal electric field of the capacitor.