What is an opamp that is suitable for designing a sensor?

[Minh Thanh]

I am finding a dual supply op-amp which has rate of voltage dropping to be low , input resistance is high about 30 -100MOhm and input offset voltage is low. All of them serve me to design a sensor that is pH sensor. Can you give me some your ideas for choosing ? Thank you !

 

[rbelli1]

It is difficult to decide without considering several considerations.

What is the accuracy that you need? What conditions will this operate in? What is your power source? Is it a battery? What lifetime do you need?

BoB

 

[jim hardy]

Search on ph meter opamp

my first hit:
http://www.linear.com/solutions/1191You need high Zin. Search on 'electrometer op amp".
I built an integrator with OPA128 electrometer opamp that'd hold a millivolt overnight with just an off the shelf polypropylene capacitor. You have to follow the datasheet directions for board layout and input guarding , though.

http://www.ti.com/lit/ds/symlink/opa128.pdf

old jim