I'm a spanish engineer student doing my end-of-degree project. I need to remove the offset of a strain gauges bridge and i'm trying to make the calibration automatic, using a DAC (digital to analog converter) that will introduce a positive or negative voltage in the REF pin of a instrumentation amplifier (i'm using INA118, but INA126 is also avaiable).
I don't want a manual calibration via potentiomenter. I've seen in the INA118's datasheet a similar circuit: Figure 27. Optional Trimming of Output Offset Voltage ( http://www.ti.com/lit/ds/symlink/ina118.pdf ).
I've seen other questions like "What is the reference pin on an instrumentation amplifier used for?" where they say "Yes, you can do a voltage shift through InAmp's REF pin", but it didn't helped.
The problem is that when i gave 6 negative volts to the REF pin in a +-2,5 supplied INA118 it burned... So i need to know what are the limit voltage in the REF pin???? With -2 volts in REF there was no problem (the limit is the supply rails maybe?)