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Automatic Capacitor Tester

IP.com Disclosure Number: IPCOM000097338D
Original Publication Date: 1962-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Woodman, GR: AUTHOR

Abstract

To permit an accurate determination of the equivalent series resistance in an unknown capacitor by means of an impedance transfer bridge, a variable frequency oscillator is used as an exciter.

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Automatic Capacitor Tester

To permit an accurate determination of the equivalent series resistance in an unknown capacitor by means of an impedance transfer bridge, a variable frequency oscillator is used as an exciter.

The relationship of Z(X), the phase of the voltage across the unknown capacitor, to X(CS), the phase of the voltage across the standard capacitor must satisfy a minimum phase angle as determined by the sensitivity of the phase sensitive demodulator used to null the bridge. That is, the output of the variable frequency oscillator must be sufficiently high so that the equivalent series resistance R(X) of the unknown capacitor is above the minimum measurable value. If the frequency is too low, R(X) will have a value below that which can be accurately resolved by the bridge.

This situation is avoided by setting R(D) to zero, R(C) to a midrange value and R(H) to an estimated suitable value based on C(unknown). The output of the VFO is increased in frequency until a minimum phase angle requirement between the voltage across C(standard) and C(unknown) is satisfied. The vector diagram shows that, when X(CS) and Z(X) are separated by a sufficient phase angle, R(X) will also have a minimum value.

The phase detector 1 measures the angle between X(CS) and Z(X). A signal is sent from detector 1 to VFO 2 on line 3 to increase the frequency, if the phase angle is too small. Correspondingly, a signal is sent on line 4, if the phase angle is outside the tolerance ...