Humidity sensor using temperature sensing resistor controlled to be at constant temperature of more than 150amp;deg; C.

摘要

A humidity sensor of a heat conduction type which enables a humidity measurement to be produced by a single temperature sensing resistor so as to reduce a change in characteristic depending on a temperature change of the measurement atmosphere and to reduce the cost, comprises a temperature sensing resistor 1 and three fixed resistors R. sub.1, R.sub. 2 and R.sub.3 which form a Wheatstone bridge circuit. The humidity is measured by utilizing the fact that the heat dissipation of the temperature sensing resistor 1 changes depending on the humidity. The temperature sensing resistor 1 is heated by a heat generator 2 for self- radiation of Joule heat so that the temperature of the temperature sensing resistor 1 is controlled to be at a constant temperature of 150. degree. C. or more. The output voltage value of the Wheatstone bridge circuit is corrected with reference to the variation of the output voltage value depending on the ambient temperature of the temperature sensing resistor 1.