PH Circuit Help

Projects General Guidance
1

Hi everyone, I designed a circuit as per TI's PDF here: http://www.ti.com/lit/an/snoa529a/snoa529a.pdf

Substituting the Op-Amp for cost reasons.(with another one they suggested) Anyway, I am having weird, slow, fluctuations in the voltage, as per my graph here

I'm thinking it's my decoupling capacitors I am using? I have two, .1uf and 47uf . Is that it? If so, why/how

Thanks in advance.

2

Looks like mains pickup beating with something probably caused by less than perfect layout.

Have you a picture of your circuit?

3

Here ya go.

4

Substituting the Op-Amp for cost reasons.(with another one they suggested)

Which one?

How/where is the input guarded?

5

Alright, I'm an idiot. I somehow didn't supply a VCC line to the OP-amp Thanks for the responses though guys.