Humidity meter

Details Humidity meter Humidity meter

1992-12-08

1994-05-31

McMahon, Timothy M.

Electricity: measuring and testing

Impedance, admittance or other quantities representative of...

Lumped type parameters

324664, 324676, 324689, 73 2901, 73 2902, 7333502, 7333503, 7333504, 7333505, 338 35, G01W 100

Patent

active

053172744

ABSTRACT:
A humidity meter includes a humidity-frequency converter (2) which is essentially a pulse oscillator, the oscillation frequency of which depends upon the impedance of a humidity sensor (1), a differentiation circuit (3) and a wave-form shaping circuit (4) which essentially operate as a pulse width modulator for adjusting pulse width of an output pulse of the converter (2) for assuring a linear relationship between humidity and the output signal, and an integrator (6) for integrating the output of the pulse width modulator to provide an output signal as a DC level. A feedback path (5) is provided to apply the output signal to the pulse width modulator for assuring a linear output irrespective of the exponential characteristics of the humidity sensor. Said differentiation circuit (3) has a capacitor (31), a first variable impedance element (32) which is controlled by said feedback path , and a second variable impedance element (33) coupled in series with the first variable impedance element (32).

REFERENCES:
patent: 4546916 (1985-10-01), Tsuaki
patent: 4703886 (1987-11-01), Kirby
patent: 4801211 (1989-01-01), Yagi et al.
patent: 4915816 (1990-04-01), Shakkottai et al.
patent: 5065625 (1991-12-01), Nakagawa et al.

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