Olimex ECG/EMG signal output, RC low pass filter output, and scope 1 kHz calibration

I found that my scope's channel 1 does not shift down the ECG wave, it is my wrong scope setting doing so.

But Channel 1 is indeed more noisy, when displaying ECG signals.

Now I am using both scope to check the same signal, so to cross calibrate.  I also check the scope's own 1 kHz calibration signal, to make sure both channels are working OK.

Now is the summary.

1. Olimex ECG/EMG outputs ECG signal more or less OK, except the 50 Hz line frequency noise is about 1Vpp.

2. Using RC filter (4K7, 2.2 uF) the noise is reduced to 400 mV.

3. Both channels display scope's 1 kHz calibration signal OK.

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