Calibration

[J-Pipe]

Dumb question, regarding the voltage calibration,

<in-use calibration value> * <accurate voltage> / <reporting voltage>

How do I get the "accurate" voltage? I assume take a multimeter reading of the voltage between phase X and ground?
Is this what everyone is doing?

[daelsc]

correct. use a high quality digital multi meter to measure voltage between each phase and neutral.