By injecting a small audio signal of 1525 Hz into the CT secondary, then measuring the induced current of the audio frequency to determine the admittance value.

Analog filtering and programmable gain are used to get the best dynamic range for the DSP to compute the admittance @ 60Hz. While CT burden needs secondary current to achieve its purpose, the admittance needs small or no current (max 0.5A) on the secondary side.

If the current is higher than 0.5A, the test will not be conducted. All the phases are done sequentially. This test can be done with or without accessory.