AD8232 giving square wave signal regardless of electrode placement

Sensors Biometrics
1

We are using an AD8232 to obtain an ECG signal.

We are using a 3-lead setup and have attached the leads to the arm, to the arm & thigh, and to the abdomen, in the 3 most common configurations seen online, on 3 different people. We have tried changing which leads were in which positions, and incrementally adjusting them at the given sites.

We were initially powering with a laptop and Arduino, but then learned about the possibility of 60Hz noise, so we switched to using a DC power supply and examining the output signal with an oscilloscope.

No matter whether the electrodes are touching skin or just air, the oscilloscope shows an intermittent square wave from 0 to 3.2V, as seen on the attached image. Changing the lead positions has no effect whatsoever on the waveform: the value is always either 0 or 3.2V.

We suspect the board is defective. Any suggestions?

2

Hi dwalford.

This can happen in two different cases:

  • - The 'patient' isn't lying down and [u]perfectly still[/u].
  • - The electrodes are not brand new and completely stuck down to the skin.
  • - The electrode cable isn't plugged into the AD8232 board all the way.

    • Make sure all three conditions are OK and give it another try. If you’re still having trouble, please post photos of the top and bottom of your board and a photo showing how it’s connected to your Arduino and we can have a deeper look.