Relative humidity detector systems and method of increasing the

Details Relative humidity detector systems and method of increasing the Relative humidity detector systems and method of increasing the

1980-09-25

1983-04-12

Woodiel, Donald O.

Measuring and testing

Gas analysis

Moisture content or vapor pressure

324 65R, 338 35, G01N 2556

Patent

active

043794068

ABSTRACT:
Sensor and method of fabricating a sensor for detecting relative humidity with a substantially linear response from 0% to 100% and also detecting temperature. The sensor utilizes a unique essentially pure Al.sub.2 O.sub.3 layer which has a disordered crystalline structure and a density gradient which varies from a low density at its lower surface to a higher density at its upper surface which together produce the desired linear response to relative humidity.
The sensor is employed as a three-terminal semiconducting device which is biased with d.c. current, allowing implementation with standard ICs and LSI circuitry. Application of a biasing current on the top electrode allows the RH sensor to be operated simultaneously as a temperature sensor.
Also disclosed is a relative humidity detector system for adjusting sensitivity of the sensor for changes in environmental temperature so as to provide a true linear relative humidity response. Periodic discharge of the d.c. biasing signal increases an already long calibration period. Additionally, use of a constant resistance biasing circuit further extends the calibration period.

REFERENCES:
patent: 3196682 (1965-07-01), Johnson, Jr.
patent: 3696360 (1972-10-01), Gajewski
patent: 4143177 (1979-03-01), Kovac et al.
patent: 4261179 (1981-04-01), Dageford
patent: 4270085 (1981-05-01), Terada et al.
patent: 4288775 (1981-09-01), Bennewitz et al.

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