I'm designing a circuit to capture the heart signal and should output it to an oscilloscope (ElectroCardiography). I need to isolate the circuit from the human, I'm using an opto-coupler for this purpose. I'm designing the circuit in MultiSim (by National Instruments). I've attached a screenshot of the circuit and a screenshot of the input to the opto-coupler and the output from the opto-coupler.
The opto-coupler is causing my signal to be reduced in amplitude and also to a have a negative DC offset.
My question is what opto-coupler should I use that would be suitable for ElectroCardiography ? I want the output to be almost identical to the input because the only purpose of the opto-coupler is isolation, so how can I get rid of any side-effects of the opto coupler ?
Please advise, thanks