Oscillators – With device responsive to external physical condition
Patent
1987-03-17
1988-04-19
Grimm, Siegfried H.
Oscillators
With device responsive to external physical condition
73767, 324DIG1, G01L 122, G01L 904
Patent
active
047392851
ABSTRACT:
A measuring oscillator for detecting different physical parameters has an all-pass filter (1) which drives a current source (16) having a controllable amplification factor and a control device (17). The control device is connected to the control input of the current source (16) and controls its amplification factor so that the amplitude of the alternating voltage produced by the measuring oscillator assumes a constant value. The all-pass filter comprises a phase-determining bipolar circuit (10) comprising a voltage follower (12) having its input connected to the first pole (9) of the circuit (10) and its output connected through bridge circuit (28) to the inputs of a differential amplifier circuit (33). The four resistance elements (29-32) of the bridge circuit have resistance values varying with the physical parameters to be detected. The output of the differential amplifier circuit is connected through an ohmic resistor (41) to the first pole. The second pole (11) of the bipolar circuit (10) is connected to the junction of the two resistance elements (31, 30) of the bridge circuit. A variation of a resistance element of the bridge circuit due to a variation of the physical parameter detected by it results in a readily measurable variation of the frequency of the measuring oscillator.
REFERENCES:
patent: 3845385 (1974-10-01), Ebrecht
patent: 4546651 (1985-10-01), Merrick
Heck Bernd
Schroder Dierk
Franzblau Bernard
Grimm Siegfried H.
Treacy David R.
U.S. Philips Corporation
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