A heart rate monitor the size of wristwatch that does not require a chest strap or another sensor at the end of a cable that could easily be lost or damaged has been demonstrated by Plessey Semiconductors. The device straps to the user’s wrist and has a sensor electrode on the rear face in permanent contact with the wrist and a second electrode on the front of the device. Touching this front electrode with a finger of the opposite hand enables the device to sense heart signals. The acquired data is accurate enough to generate detailed ECG plots with suitable signal processing, including precise pulse rate and pulse rate variation.
Plessey has also designed a version for continuous heart monitoring. It straps on to the upper arm and has two contacts on the inside of the strap. They are positioned such that the detected cardiac signals are out of phase, yielding a differential signal with a high signal to noise ratio. This allows unwanted noise artifacts from other muscles to be filtered out to obtain a detailed ECG trace. With this device, patients could be monitored while they go about their daily routine, enabling detection of transient issues that would probably be missed during short monitoring periods with conventional ECG instruments.
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