The conductor carrying the current to be monitored is threaded through the aperture in the transformer. This effectively forms the transformer's primary winding. The enclosure of the instrument consists of a painted metal case which is electrically joined to the screen of the connector. Adequate insulation should be provided between the conductor and the case of the instrument.
The current tranformer is terminated and calibrated at the time of manufacture and needs no further adjustment. Its voltage output is directly proportional to current and may be modelled as a voltage generator in series with a 50 ohm resistor over its bandwidth. The output is taken via a matching cable and fed into a measuring instrument such as an oscilloscope or voltmeter. If the input impedance of the measuring device is high ( e.g. greater than 50k) then the current flow is equal to the recorded voltage divided by the sensitivity of the transformer.
The direction of current flow which gives a positive output signal is indicated on the monitor.
Lilco current transformer measuring the short circuit output current of a pulse generator
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