As far as I understand, normally an ideal differential amplifier(or an instrumentation amp) can reject common mode(CM) voltages up to around its rail voltages.
Let's say the rails of the diff. amp are +/-10V DC. And let's say the inputs are such that the normal/differential mode voltage is 1V, and the common mode voltage is 20V. As far as I understand, this will saturate or maybe damage the amplifier because 20V>10V. But if the common mode voltage at the input would be 2V this would be rejected well and the amplifier would work fine because 2V<10V.
There is this signal conditioning module and below is some specs from the data-sheet:
I know that after this signal-cond. module, the signal are coupled to data acquisition inAmps whose rails are +-5V.
Normally if there were no conditioning a 20V common mode voltage would saturate the amplifier. But this module says "CMV, Input to Output 1500V max."
Does that mean that the module can get rid of a common mode voltage of 200V or more? I also came across the following:
Does that mean the 5V battery above can be read as 5V even though Vcm=1200V? Is that what this module doing and acting as a common mode filter or choke?