Specifications
15-394 | OWNER’S GUIDE
Avoiding Common Mode Issues
In contrast to isolated ampliers the input common voltage range is limited at differential ampliers. The
measurement conguration below shows the possibilities to measure the current of a 24 V supplied system.
The optimum input range in that case is 500 mV. That will work ne for CH1 in the picture, but not for the
CH0. This channel will exceed the maximum common mode voltage and go into overow.
With the MDAQ-SUB-V-200 module, there are several ranges which overlap between the 12V and 250V
max CMV ranges. This is intentionally done to provide you with more options when it comes to choosing the
best possible t of range/resolution/common mode.
The max. CMV is shown here within the software (analog channel setup dialog):
Notice that in the screen shot above left, the CMV is shown to be 12V max, whereas it is 250V max in the screen shot above
right.
⇒ Always pay attention to the max CMV which is listed on the channel setup screen, when you
select a given range within the software.