It can work with any sensors in dual mode where they are operating separately but for ratio or difference it can only work with pyro vs. pyro or thermal/photodiode vs. thermal/photodiode.
This can be done with the Spagent program and a Kiethley GPIB PC card. Please contact Ophir engineering for details.
We have a special plug which allows this. Ophir P/N 1Z11006.
Offset is entered for each sensor separately. You choose "Active Sensor: A", then set offset for sensor A in the usual manner, then go back and choose "Active Sensor: B" and repeat. This also makes the most sense, since each sensor might in fact need a separate offset.
Please note: After activating “OFFSET” for each sensor separately, when you then work in “BOTH” mode, you no longer see “OFFSET” shown on the screen; nevertheless, the “OFFSET” function is still in fact working.