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I have a similar circuit like

https://www.egr.msu.edu/classes/ece480/capstone/spring15/group05/uploads/4/7/5/1/47515639/ece_480_app_note_justin_bauer.pdf 2. page bottom

Wheatstone bridge: 2x 350 ohm strain gauge (GF 2, 0.3%, 6-12 ppm) 2x 350 ohm resistor (0.1% 25 ppm)

I measure 40 ppm, so the resistance change is only 0.028 ohm.

How could I nullify the error that comes from the tolerance of the resistors the offset of the in-amp and temperature change?

For the first part of the question I found that simple voltage divider at the reference is an okay solution and the temp change doesn't have such a great effect.

The task is to drive a JFET if I measure more than 40 ppm, so I'd put the JFET to the output of the in-amp and set the REF voltage so if I get say 41 ppm the few uV difference with the amplifier is enough for the JFET to open. Is there a better, easier solution for this problem? Is "my" solution okay?

In another question Spehro Pefhany suggested AD8237 instead ina-128.

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