ACCURACY OF WOOD RESISTANCE SENSORS FOR MEASUREMENT OF HUMIDITY

This work was undertaken to evaluate the accuracy of wood resistance s ensors for measurement of relative humidity and to identify sources of error in this use. Relative humidity can be expressed as a function o f the logarithm of the sensors electrical resistance and of its temper ature. We found that single-point calibration of each sensor compensat es for most between-sensor variation, although care must be exercised during calibration. With careful calibration readings, error in relati ve humidity readings made with these sensors can be limited to +/- 10% relative humidity under most conditions. The literature indicates tha t a lower degree of error than this is anticipated when electrical res istance is used to estimate moisture content measurements. Our data su ggest that sorption hysteresis and sensor memory are significant contr ibutors to this (+/- 10%) relative humidity error.