ph sensor?

[edfcmc]

Is there a linear PH sensor? Or a circuit that can be canabilized for a ph sensor?

[Chris Foley]

Information on pH sensors and meters is available at www.omega.com. Also, there is good technical reference material at the Omega Engineering site, at http://www.omega.com/techref/

[Dimbulb]

Really nice ph meter can be very hard to design.
An op-amp wheatstone bridge is carefully balanced stable by a reference voltage and compensated for thermal changes that cause errors both in circuit and probe also the output may not be linear requiring more compensation. I have wondered if a 12 bit a/d pic thermistor temperature kit could be modified so that a homemade ph probe would balance changing the bridge and letting the PIC software correct the errors.