I built a circuit on a perf board, see schematic below. Basically, I have an analog sensor where the output is a Wheatstone bridge. I connect this to an instrumental amplifier (AD623ANZ) with a gain of ca. 20 and I filter the output with a first order active low pass filter (fc=100Hz).
My goal is to sample this signal with the ADC of my Nucleo board (NUCLEO-F070RB). First thing I do is to check the noise level of the filter output with the oscilloscope before connecting it to the nucleo. So far so good, photo attached.
As soon as I connect the output to the nucleo, the signal is much worse. I see spikes every 100ms, suspiciously this is due to the adc sampling = 10Hz, and increased noise. Again photo attached.
Some more info: 1. the perf board and the nucleo have the same 5V supply; 2. I use a 20cm wire to connect the filter output to the adc input.
What do I miss? How can I get rid off the increased noise + spikes?