Simple Instrumenatation Amplifier Circuit

[Roff]

I have seen this same reply on two other websites.
You need to use a medically-approved isolation part. A cheap unapproved transformer might short and electrocute the patient. A opto device might also short.

On another forum, I suggested DCP01 and ISO124 from TI. DCP01 may not be safe for medical apps.

 

[keane2097]

I have seen this same reply on two other websites.

I don't see why you continually make an issue of this - you post on several sites, why shouldn't I? I want to get as much advice as possible in order to complete my design as well as possible, what's wrong with that?

You need to use a medically-approved isolation part. A cheap unapproved transformer might short and electrocute the patient. A opto device might also short.

Thanks for this, I'll look into purchasing an isolation component. I was under the impression that an opto-coupler would be incapable of providing a device with power, is this incorrect?

 

[keane2097]

On another forum, I suggested DCP01 and ISO124 from TI. DCP01 may not be safe for medical apps.

Thanks, I think I'll probably get the ISO124...

 

[Roff]

Thanks, I think I'll probably get the ISO124...

It appears from what little searching I did that most ECG preamps are battery powered, with an isolation amp taking the signal to the processing circuitry.

 

[keane2097]

It appears from what little searching I did that most ECG preamps are battery powered, with an isolation amp taking the signal to the processing circuitry.

Is that not more to protect the circuitry rather than the patient though?

 

[ericgibbs]

Is that not more to protect the circuitry rather than the patient though?

hi keane,
Its to protect the patient from an electric shock.

Use a low voltage battery solely for the preamps, after the signal is amplified and filtered use an approved isolation amp to connect to the 'main' part of the equipment.

Another way that can be used is digitise the signal just after the preamp/battery stage and use and opto-coupler for the digital output.

However, for medical use, this method may not be approved,

Ensure that the equipment meets ALL the statutary safety rules, you dont want to be sued by a patient in the event of an accident.