EKG Sensor Not Working

[IrishTechAssistant]

Hello,

I am designing a project for university students by having them program the
EB031 ARM Microcontroller and acquiring the EKG signal and then graphing
it using a visual studio WPF file.

This project has been successfully done using the Spirometer device, however
I have tried to use the EKG Sensor and I am not getting any signal other than
the baseline reading. I have attached the electrodes as indicated in the instruction
booklet and I have used two different EKG sensors neither worked.

With other sensors I get a variation in the signal, so the problem is either with the EKG sensors
or with the setup.

Has anyone else encountered this type of problem before or has any ideas on how to fix it?

[Steve]

According to the datasheet, the "lead II" configuration is the one that produces most variation, so I'd suggest using this.

Lead II:
• Put an electrode patch on the right upper arm. Connect the green (or negative)
alligator clip to the right upper arm electrode patch.
• Put an electrode patch on the inner surface of the left thigh. Connect the red (or
positive) alligator clip to the left inner thigh electrode patch. Note: Instead of
the left thigh, you can use the inner surface of the left ankle just behind the left
ankle bone.
• Put an electrode patch on the inside surface of the area behind the right ankle
bone. Connect the black (or “reference”) alligator clip to the ankle electrode
patch.
• Drawing an imaginary line between the red and green electrodes yields an
oblique line from the right shoulder towards the left leg. Lead II generally gives
the greatest variation of impulse and is the EKG usually shown in movies, text
books, etc.

Here is some more information:

Use three electrode patches per subject. The electrodes can be reused, but they tend
to absorb moisture (they are very hygroscopic) and, therefore, reuse is not
recommended.
Note: Once opened, the electrodes should be kept refrigerated in a clean, dry, airtight
container for storage. Even with air-tight storage, opened electrode packages
cannot be stored from one year to the next.
Because the electrical signal produced by the heart and detected at the body’s
surface is so small, it is very important that the electrode patch makes good
contact with the skin. Scrub the areas of skin where the patches will be attached
with a paper towel to remove dead skin and oil.

And something else I've found:

Is an EKG trace visible? If the QRS complex (big spike) in the EKG trace is not visible then there is either a problem with the EKG sensor or a problem with the subject. To test the EKG sensor, collect data while shaking the leads when they are not attached to the subject. You should see a change in the trace. If you do not see a change, something could be wrong with the leads or the sensor.

In a few cases (less than 12%) the subject’s skin may not be conductive enough to pick up a good EKG trace. Abrasive / conductive electrode gel and clinical grade EKG electrodes may need to be used in this case. The easiest way to test this is to record an EKG from another individual. If you get a good EKG from another subject skin conductivity is the problem.

I hope something in this post helps.