Electricity: measuring and testing – Conductor identification or location – Inaccessible
Patent
1978-10-30
1980-08-05
Karlsen, Ernest F.
Electricity: measuring and testing
Conductor identification or location
Inaccessible
324 60C, G01R 2702, G01R 2726
Patent
active
042164249
ABSTRACT:
An Equivalent Series Resistance (ESR) measurement device for testing electrolytic capacitors without removing the test capacitor from the circuit in which it is being used and without first discharging the test capacitor prior to testing. A low voltage AC ohmmeter, which operates at a frequency of approximately 100 KHz, is used as the measurement device for the in-circuit testing of the ESR and thus as an indication of the status or usability of the electrolytic capacitor being tested. A current-blocking capacitor is placed in series with the electrolytic capacitor being tested to allow in-circuit testing without damaging the meter since it blocks any DC charge remaining on the test capacitor. A pair of oppositely poled diodes are coupled in parallel across the terminals of the meter to protect the meter from surge currents and the like and a resistor is coupled in parallel with the test capacitor to provide a discharge path for discharging the series blocking capacitor when the electrolytic capacitor is removed from testing. The ESR meter itself is designed with two operational amplifiers forming an oscillator whose output is relatively immune from fluctuations in supply voltage. An amplifier network including three operational amplifiers is provided to amplify the ESR signal to a usable level. A peak-to-peak detector circuit is used which employs an operational amplifier having a supplemental feedback resistor which reduces the phase shift at the output of the operational amplifier to enable the peak detector diodes to perform their conventional functions. The two outputs of the peak detector are connected to two DC amplifiers and a conventional meter movement is driven differentially by the DC amplifiers to provide a visual readout of the measured ESR of the test capacitor for evaluation purposes and the like.
REFERENCES:
Willihnganz, E.; "A Bridge For Measuring . . . ", The Electrochemical Society, Preprint 79-20, Apr. 1941, pp. 255-256.
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