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I have a INA126 IN-Amp. I hope to use it with a ph probe. But I am not sure exactly how to do that. should I put the probe in series with a branch of a resistive wheat stone bridge, or just tie it to the refrence voltage?

I am using +5V with a reference at 2.5 volts. A schematic would be really nice if anyone can show me something like that.

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http://www.all-about-ph.com/images/simple-construction-of-a-ph-meter.jpg The internet has lots of schematics that are way complicated, can't work, or need parts you won't easily find.

This should get you started. Any op-amp with a bias current in the pA range and will operate on 5 volts will work. This circuit does not include temperature compensation, but if you work anywhere near room temperature the errors will be small. Any questions? Forget the 1N126 and the bridge circuit.

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