ABSTIMMVERFAHREN UND -EINRICHTUNG FUER KAPAZITAETSMESSBRUECKEN

For detecting small variations in capacitance in a specimen 3 under test, a HF generator 1 supplies HF current through a quadruple balun transformer 2 to a parallel resonant circuit including the specimen 3, a capacitance diode 5 and an inductor 7, and a pre-amplifier 9 is connected to a phase sensi...

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Bibliographic Details
Main Authors BREITENSTEIN, OTWIN. ER.NAT., DDR 4020 HALLE, DD, HEINZE, EKKEHARD. ER.NAT., DDR 1193 BERLIN, DD
Format Patent
LanguageGerman
Published 18.05.1989
Subjects
MEASURING
MEASURING ELECTRIC VARIABLES
MEASURING MAGNETIC VARIABLES
PHYSICS
TESTING
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Summary:For detecting small variations in capacitance in a specimen 3 under test, a HF generator 1 supplies HF current through a quadruple balun transformer 2 to a parallel resonant circuit including the specimen 3, a capacitance diode 5 and an inductor 7, and a pre-amplifier 9 is connected to a phase sensitive rectifier (not shown) to produce an output representing capacitance variation of the specimen 3. Bias voltages U1, U2 are applied to the specimen 3 and the capacitor 5 and a compensating HF current is applied to the pre-amplifier 9 with 180 DEG phase shift via FET 8 controlled by a voltage U3. A gate 11 under the control of U4 switches the input of pre-amplifier 9 to compensate for relaxation time effects of the specimen 3. Balance of the apparatus is achieved by firstly applying a control voltage U4 to FET 11 to reduce the gain of pre-amplifier 9. Control voltage U5 is then adjusted to achieve balance.
Bibliography:Application Number: DE19883828856