You can use either one that will give you a consistent reading and can "sense" your pulse. It is based on transmitting the light from one side to the other side and the blood flow between the two will show fluctuations in the light so it "reads" your pulse. I use the ear clip and have better consistent results. Same for me and my wife. Although we may have to use the finger clip on her soon, as her ear pulse is sketchy sometimes due to her much lower blood pressure. I have tried the 'web" between thumb and forefinger as others have tried to no avail (fat hands).
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