"Common Mode Voltage." The voltage which is tolerable between signal and ground.
The AC or DC voltage which is tolerable between signal and ground. One type of CMV is specified between SIG LO and PWR GND. In differential meters, a second type of CMV is specified between SIG HI or LO and ANA GND (METER GND).
This specifies the DC voltage which is tolerable between input low and power ground. When the equipment is operated from logic level power the CMV is apt to be in the order of 0.5 VDC or less. Using batteries or a transformer-isolated power supply permits an instrument to be operated at a higher CMV, usually in the order of 100 VDC when related to panel instrumentation. In a differential measurement system, the common mode voltage usually represents an interfering signal. The common mode voltage is the average of the voltages on the two input signal lines with respect to ground level of the measuring system.