Opto-isolator

[GSR]

Dear all,

I am building up an analog circuit for Electromyography (EMG) data collection, but I have to put isolation between the circuit and the human subject. A possible solution may be opto-isolator, does any opto-isolator support analog input and analog output?? I read wikipedia which says opto-isolator is using an LED inside the chip. If so, there may have some forward vlotage bias in the signal???

[PaulG.]

Dear all,

I am building up an analog circuit for Electromyography (EMG) data collection, but I have to put isolation between the circuit and the human subject. A possible solution may be opto-isolator, does any opto-isolator support analog input and analog output?? I read wikipedia which says opto-isolator is using an LED inside the chip. If so, there may have some forward vlotage bias in the signal???

Something like this?

[GSR]

Something like this?

Yes!!!!

[Rolf Kalbermatter]

Yes!!!!

But if you want to use those sensors on humans you will not want to make the isolation yourself. There is basically no way you can get the necessary approvals yourself, that you can not get into trouble if a patient suddenly feels sick after having been subjected to a physical contact with the sensors isolated by your circuitry.

And getting sued can be very expensive.

[EricLarsen]

If you were building an EMG to use on dung beetles, I'd say go for it and build one yourself. On human subjects, or even cute and/or edible animals, no way. Like Rolf said, approvals for human trials can take years and cost MANY times what the equipment itself costs.

Correct me if I'm wrong, but doesn't EMG involve piercing the skin with electrodes? A leakage current of as little as 5 millamps applied in the wrong spot can kill a person.

There was a topic that came up on the info-labview board years ago by a person who was doing EKG measurements on pigs. He'd hook up the EKG leads to the data acquisition box and the pig would die from cardiac arrest. Ground loops can be a real bummer.....