Karolina_1
Member level 3
Hi, I was trying to build lock in amplifier as it was explained in Instructables with simple AD630, AD620, OP27 and 3rd order low pass filters(R1=R2=R3=10kohm C1=C2=C3=3.3microF). I generated reference and input signal from signal generator and made their phase and frequency equal. Ref and input signal are phase locked loop inside the signal generator. Reference and input signals are both 200mVpp or 70.7mVrms, f=1kHz. I adjusted both AD620 and OP27 gain to 10. AD620 working fine, i can see 700mVrms & 2Vpp f=1kHz and after demodulation Vpp=2 and Vrms becomes 0.61mVrms, f=2kHz. After some filters and OP27 at the output i see 11.1V DC. I think i was supposed to see 7V DC.(70.7mVrms*10(gain)*10(gain))I want to use this lock in amplifier as a voltmeter to measure signals in noisy environment. How output DC voltage and input signal are related? Maybe filters gain is the reason for wrong output. I took out the 100microF capacitor at the output.
More detailed explanation of project is here.
https://www.instructables.com/id/Lock-in-Amplifier/
Best regards
Thank you
More detailed explanation of project is here.
https://www.instructables.com/id/Lock-in-Amplifier/
Best regards
Thank you