Hi:
Sorry, here is a misunderstanding. I wanted you to disconnect Left-Arm and Right-Arm ECG signal
source, and let the INA321 just look into 4K7 test resistor allone.
At this preliminary stage, I'm not interested in the AC signal, all I want to see is the "V output signal",
DC coupled, at the time base settings I had previously requested. Thanking you.
Bye for now.
---------- Post added at 22:51 ---------- Previous post was at 21:48 ----------
So for clarification:
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In the original Texas Design:
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The ECG probe is connected via 2 x 100K0 series resistors, so in order to test this circuit in my rig,
I would connect my 4K7 resistor in place of the ECG Left Arm and Right Arm electrodes.
In your design case, it would mean.
That the 4K7 test resistor, would be in place of your ECG "Left Arm" and "Right Arm" electrodes.
So what I'm looking for is a clean DC signal, coming out of "V output".
So what I would be looking out for are :
DC-Coupled test:
Do some preliminary calculations to establish the proper
operating parameters for INA321 and the "Active filter OP-Amp"
Monitor the Vr= it should remain stable.
AC-Coupled test:
Is their any noise, any beating 50 Hz
Any noise, any hunting, any spurious signals would indicate very severe problems some where.
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Disconnect my 4K7 test resistor, and connect your ECG signal again.
Monitor the junction of R10 and R11 and see if the voltage remains stable at at
+ 2.5 volts.
Take a look withthe oscilloscope at the active filter, from either end.
Investigate where the beating comes from, which is so visable on the oscilloscope.
In my humble opinion, you do not need a "Shield drive" to get a reasonable ECG signal,
and with 3 chips and a few resistors and caps you are in the business. Shield drives
are an art form, and not for the light hearted beginners.
Think about it.
Good luck.
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