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Ph electrode and Reference electrode amplifier recommendation

ambar rathie
Prodigy 95 points
Other Parts Discussed in Thread: LMP91200, INA116

I am using pH[16-705] and reference electrode[16-702] from Microelectrodes.

I need recommendation on instrumental amplifier and voltage buffer amplifier.

Amplifier requirements are:

1) Amplifier application needs to be for Ph measurement

2) Amplifier need to have very very low input bias current, as low as FemtoAmps if possible

3) Amplifier needs to very high input impedance up to 1000 G ohms if possible

3) differential mode configuration for low CMRR

I looked at LMP91200 but it requires a controller to set the gain. I am ok with two different chips and  connect them together as a voltage buffer followed by [differential amplifier with RC filter]. 

Any recommendation would be greatly appreciated.

  • 0
    Expert 1095 points

    Hi ambar rathie,

    For pH measurement I think you can use this:

     For INA116P, maximum input bias current is around +/-25fA and typical range is around +/-3fA

    http://www.ti.com/lit/ds/symlink/ina116.pdf

  • 0 in reply to Deepak%20murali
    Prodigy 95 points

    Hi Deepak, 

    1. One of the problems I would like to solve is the noise introduced in the circuit by fluorescent light  in the lab room. How can I solve this problem? 

    2. Secondly, I want to avoid any noise introduced by DC power supply. Noise on the ground and power side. 

    3. Does TI make 4-opamp instrumental amplifier instead of 3-opamp like INA116?

    As far as pH probe goes I am only dealing with 1Hz input frequency so anything thing above that need to be taken out. 

  • 0 in reply to ambar rathie
    Prodigy 10 points

    Hi! I would like to share this great online resource for anyone seeking a pH electrode : http://www.directindustry.com/industrial-manufacturer/ph-electrode-75414.html