I have built this circuit on breadboard with the help of previous threads on this forum and example circuits in instrumentation amplifiers data sheets. Unfortunately I'm getting a very noisy signal (see the plot and spectrum). I tried mitigating this noise with a 60Hz notch filter thinking it was this type of noise the source of it but it resulted in no avail. The leads are shielded and twisted together so I think this is not the problem. So I wonder if there is anything I can do to increase the SNR??