This may sound a weird question but couldnt resist to ask here.
Lets say I have a differential signalling mode floating battery powered transducer(where the outputs are mirrored) and the differential voltage across its outputs Vd at a moment is 1V.
Lets call the output wire pairs as V+ and V-. At this moment I only know the differential voltage between V+ and V- by using a voltmeter or a scope as 1V.
Below illustrates the transducer and its differential outputs:
But in the above situation I dont know the voltage across V+ and the earth ground and similarly I dont know the voltage across V- and the earth ground.
Lets say I measure the voltage across the V+ and the earth and V- and the earth and I measure them as 101V and 100V respectively keeping the differential voltage as 1V again.
Imagine I hook up this transducer outputs to a differential amplifier where its system analog ground is earth grounded. I draw the equivalent circuit as:
In this case, the common mode voltage Vcm = (100 + 101)/2 = 100.5V
the differential voltage remains Vd = 1V
If it is true so far so good..
But in data-sheets of the amplifiers there is something called input common mode voltage range. I think it is the max voltage an amplifier can handle with respect its system ground.
And imagine this amplifier has +/-15V input common mode voltage range.
My questions are:
1-) Would the amplifier get damaged in this case?
2-) If it would, does that mean that I have to measure the differential output pairs of the transducer one by one with respect to system ground of the amplifier each time before I couple them? Is there a common practice for that?