This article is to give you some insight for VFD applications when using the Fluke-377 FC or Fluke-378 FC.
The FieldSense technology is not intended to measure the output signal of a variable-frequency drive (VFD) motor controller for either voltage or current. The FieldSense technology is built into the Hard Jaw portion of the two Clampmeters.
The work around is to use the AC voltage mode and the test leads if you need to measure the output voltage of the VFD and use the iFlex mode and the iFlex current probe to measure the output current of the VFD.
The manual does state the following: