Electrode measurement to determine plates of capacitor - has AC electrode detection of voltage to determine outer capacitor plate prior to insertion in metal case

摘要

The measurement technique is used to determine which is the outer electrode of a capacitor during production but prior to sealing in the case and is particularly important with regard to electrolytic capacitors where the outer must be connected to the can and where it is visually impossible to determine by inspection which lead out wire is the outer capacitor electrode. A measurement electrode (1) is located inside a screen electrode (2) which is connected to an overall earth screen (3). The capacitor (4) under test has the electrode connections (5,6) connected to an a.c. generator (7). The measurement electrode (1) is connected to the input of an impedance changer circuit (8), with output taken back to the screen (2), and followed by a frequency selective amplifier (9). The amplifier (9) is tuned to the measurement frequency and the output is rectified (10) and the voltage measured (11). The voltage differences for capacitor connection reverses (5,6) are used to determine which electrode is the outer. Differences with a ratio of 37:1 are obtainable.