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Resistance Controlled Oscillator

IP.com Disclosure Number: IPCOM000095053D
Original Publication Date: 1965-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Fant, WJ: AUTHOR [+3]

Abstract

This oscillator provides an output signal having a frequency which varies as a function of the resistance of one arm in a bridge circuit. The oscillator consists of five sections.

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Resistance Controlled Oscillator

This oscillator provides an output signal having a frequency which varies as a function of the resistance of one arm in a bridge circuit. The oscillator consists of five sections.

In the bridge and mixer, either R1 or R2 can be the sensor. The sensor resistance changes with the measured variable. R1 and R2 are equal for one value of the measured variable. R3 and C1 form a phase-shifting network called the quadrature network. This network provides a voltage having a phase shift from 1 to 180 degrees of lag with respect to Vo/2. as frequency goes from zero to m. R6 and R7 are equal and form a reference source for Vo/2. R5 attenuates the output of the quadrature network. Q1 prevents R5 from loading the quadrature.

If the frequency of oscillation when R1 = R2 is assumed to be omega = 1/RC, the phase contribution of the quadrature network is -90 degrees. There is no contribution from the sensor network.

If R1 differs from R2, some in-phase voltage, positive or negative, appears and, when summed with the quadrature voltage, the resultant is no longer 90 degrees.

The differential amplifier subtracts the quadrature voltage from the in-phase sensor voltage, producing the resultant described above. It introduces no additional phase shift.

The AGC section can be a variable resistance device, a clipper, or a combination of both. For best results, it is referenced to the output voltage of the system. It prevents saturation of amplifier stages...