Heart-rate monitoring is popular among runners and other fitness-minded individuals. But having to fuss with awkward chest straps and gels can be bothersome. Utilizing its EPIC sensor technology, Plessey Semiconductors is now attempting to streamline the process. The company has designed a wristwatch-sized heart-rate monitor that does not require a chest strap or second sensor at the end of a cable.
Like a watch, the device straps to the user's wrist. It includes two sensor electrodes: one on the rear of the device (which remains in permanent contact with the wrist) and a second on the front of the device. Simply by touching the latter sensor with a finger from the opposite hand, the user can collect electrocardiograph (ECG) signals.
The EPIC sensor measures changes in an electric field in a way that is similar to how a magnetometer detects changes in a magnetic field. Requiring no physical or resistive contact to make measurements, it can be integrated on a chip with other features (including data converters, digital signal processing, and wireless-communications capability). The technology works at normal room temperatures.
Plessey has also designed a second version of the deviceone that provides continuous heart monitoring. This device, which straps to the upper arm, features two contacts on the inside of the strap. Those contacts are positioned so that the electrical cardiac signals are out of phase. The result is a strong differential signal-to-noise ratio, filtering out unwanted noise artifacts from other muscles.