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I am an industrial designer (little experience with electronics) trying to modify one of the AD8232 chip configurations. The AD8232 is a Single-Lead, Heart Rate Monitor Front End. In the datasheet, page 24 there is an exercise to measure heart rate signal at your hands with steel electrodes. This is the one (see image below) I would like to modify to get a good signal from steel electrodes, but without the right leg electrode.

enter image description here

I am working on a breadboard using a breakout for the AD8232. So far I do not get good results, I tried to use a configuration like can be seen below.

enter image description here

I need help with the configuration and setup, perhaps there are better ways to achieve the end result, I am open to ideas. Thanks.

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  • \$\begingroup\$ Without a knowledge on CMRR using active guarding using RLdrive feedback or RLDFB contact, how can we explain why this is important? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 14 at 16:56
  • \$\begingroup\$ first thing first ..... do you get good results if you use the leg electrode? \$\endgroup\$ – jsotola Mar 14 at 17:23
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    \$\begingroup\$ Quote from the datasheet: The RLD circuit drives to the third electrode, which can also be located at the hands, to cancel common-mode interference. \$\endgroup\$ – AltAir Mar 14 at 18:07
  • \$\begingroup\$ @jsotola yes I get good results using it. \$\endgroup\$ – Kevin Mamaqi Apr 8 at 19:31
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You probably don't want connections from RLD to BOTH arm electrodes. I suggest trying to connect to only ONE of the arm electrodes, through \$360k\Omega \$, and not \$10M\Omega\$. You want to use one of the arm electrodes as the reference, and you don't want to separate it with large impedance.

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  • \$\begingroup\$ Although I still don't understand very well the principle behind our recommendation, it works better as you suggested. Moreover, I would like to know a bit more. What do you mean by You want to use one of the arm electrodes as the reference, and you don't want to separate it with large impedance? - What do you mean by separate? \$\endgroup\$ – Kevin Mamaqi Apr 8 at 19:30

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