The Add/Subtract I/O adds or subtracts data of two or more sources. Up to 32 sources can be added or subtracted with a Add/Subtract I/O.
A typical application of the Add/Subtract I/O is performing a differential measurement using two channels. When the high voltage and the low voltage of the differential signal are measured, the differential signal can be calculated by subtracting the low signal from the high signal.
To control the behavior of the Add/Subtract I/O, several properties are available. These can be accessed through a popup menu which is shown when the I/O is right clicked.
The +- mask determines which sources are added and which sources are subtracted. This mask contains a '+' or '-' character for every connected source. By default, the mask consists of '+'-es only and all sources are added. To subtract a source, set its corresponding mask character to '-'.
Some examples of +- masks are shown in the table below:
|2||++||src1 + src2|
|2||+-||src1 - src2|
|2||-+||src2 - src1|
|2||--||-src1 - src2|
|3||+--||src1 - (src2 + src3)|
|6||+-+--+||(src1 + src3 + src6) - (src2 + src4 + src5)|
To invert a source, you can use an Add/Subtract I/O with a with a mask that is '-'.