AC (RMS) / DC (Mean) / Frequency values
The Channel Checker shows 4 values for each channel input:
AC+DC (RMS)
Geometric sum of the AC and DC values. May not match the numerical sum of the AC and DC values.
AC (RMS)
AC-only RMS value of the signal input.
DC (Mean)
DC-only value of the signal input.
Frequency
The frequency count of the signal. Firmware v4.0.5 and above calculates this based on the zero-crossing of the signal, firmware prior to v4.0.5 calculates frequency based around the mean-value of the signal.