1. What does a sow's ear have to do with anything? What are you trying to s=
ay?

The guy got more than reasonable results with the components used. I
don't mind those results. If he did not get reasonable results, I
would not replicate his experiment.

2. Yes, the parts are cheap, but I'm not going to pay $20 to ship 3 ICs

On Wednesday, January 26, 2011, RussellMc <apptechnz@gmail.com> wrote:
>>> There are some jobs where you need to come withing spitting distance
>>> of the correct solution to make it worth doing at all. This is one of
>>> them. Use of very or very very =A0inferior opamps, unbalanced resistors
>>> and out ofspec cap values is going to make life interesting.
>>>
>>
>> I'm not saying that I don't believe you guys, but the fact that the guy =
got
>> good results (http://www.eng.utah.edu/~jnguyen/ecg/bigecg.gif) motivates=
 me
>> to continue with this schemtic. He used 5% resistors, even.
>
> Yes, even sows' ears can be used to measure heartbeat.
> Also note the opamp comment.
> He uses these.
> Not overly costly at Digikey
>
>  =A0 =A0 =A0 =A0 =A0 http://www.fairchildsemi.com/ds/LF/LF353.pdf
>
> Try writing up the basic equations for the amplifier and plug in 5%
> resistor values. It will 'work' but you'll =A0rather hope your common
> mode signal is not high.
>
>
> =A0R
>
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