how can i reduce noise signal in ph circuit?

Question

i made ph circuit by using ph electrode and then amplify the output signal but there is a problem that i faced, there noise signal enter in circuit and i want to use filter to reduce it ,i dont know the range of frequency that electrode work in it(trade mark of electrode is pH-electrode sentix 20)

Answer 1

You are measuring pH which is a fairly steady state observable. That makes the noise filtering very easy. You can add low-pass filters by letting high resistance drive high capacitance. Something like 10 KOhm driving 10 uF would give you a -3dB low pass pole at 1.6 Hz. Any noise higher than 1.6 Hz would be rolled off by 10 dB for very count of 10 times 1.6 Hz of frequency distance. That is 16 Hz would be 10 dB down, 160 Hz 20 dB, 1600 Hz 30 dB. You can put more poles on the circuit by adding more RC as needed, filtering is a linear operator, the effects of multiple of them add.

Alternatively you can sample the noisy readings many times and let the Central Limit Theorem reduce the dispersion of you data. If you quadruple the count of your averaged samples their standard deviation will shrink by one half.