Channel 4 is usually used to measure the neutral line of a 3-phase 4-wire system.

Because Channel 4 is isolated from the other channels, the following applications are also possible.

1. DC measurement with channel 4

This has wide applications for monitoring the DC power supply system or the internal power supply systemof equipment.  Model PW3198 can detect events for DC values, allowing you to see the impact to the AC power supply measured by CH1 to CH3 when there is a problem on the DC power supply.

2. 2-circuit measurement with channel 4

Model PW3198 can measure another circuit from CH1 to CH3 (except power values). For precise measurement, the circuit measured by CH4 should be synchronized to the circuit measured by CH1 to CH3.

Source : Guidebook for Power Quality Measurement, HIOKI E.E. Corporation