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How are maximum input voltage and maximum common mode voltage related on the
Integra series (e.g.77xx) modules?
Each analog channel on a 77xx switch module has a HI and a LO terminal for connection of the
signal of interest. This connection has a maximum signal level specification. Additionally, the
77xx module has a Common Mode Voltage specification. Common mode voltage is the potential
difference between the 27xx mainframe's chassis ground and the HI or LO terminals. In effect, it
is the amount by which the signal can be floated relative to chassis ground.
The input voltage and common mode voltage are listed as follows.
Switch Maximum Maximum Voltage Maximum Voltage
Module Common Mode between module HI between module
Voltage(VCM) and LO HI and LO
Assume MAXIMUM Assume
VCM VCM = 0V
7700 300V 0V 300V
7701 300V 0V 150V
7702 300V 0V 300V
7703 300V 0V 300V
7705 300V 0V 300V
7706 300V 0V 300V
7707 300V 0V 300V
7708 300V 0V 300V
7709 300V 0V 300V
7710 300V 0V 60V
7711 0V 60V 60V
7712 0V 30V 30V
The maximum allowed input voltage at the HI and LO terminals is the difference between the
maximum allowed common mode voltage (from specification) and the actual common mode
voltage present in your system.
For example on the 7700 module where the common mode voltage specification is 300V and the
maximum input voltage specification is 300V: