Heart monitor in a wristwatch

A heart rate monitor using EPIC sensor technology, which is the same size as a wristwatch, has been produced by Plessey in England.

The device does not require a chest strap or second sensor at the end of a cable that could be easily lost or damaged. The reference design shows that simple and effective personal monitoring of electrocardiograph signals can be as easy as taking a pulse.

The device straps to the wrist with a sensor electrode on the rear in permanent contact with the wrist and the second electrode is on the front. Touching this top electrode with a finger from the opposite hand enables the device to collect the heart signals.

The data gathered is accurate enough to provide detailed ECG signals with the appropriate signal processing, including precise pulse rate and pulse rate variation. This opens up the possibility of estimating key aerobic performance parameters such as VO2max.

The company has also designed a version to provide continuous heart monitoring. This device straps to the upper arm and has two contacts on the inside of the strap.

These are positioned so that the electrical cardiac signals are out of phase to give a strong differential signal to noise ratio so that unwanted noise artefacts from other muscles can be easily filtered out to give a detailed ECG trace.

Such a device would enable patients to be monitored as they go about their daily routine and detect transient issues that would probably be missed during a short period of monitoring with the conventional seven electrodes and gel approach.

The company will not be manufacturing the monitors, which have been created to demonstrate to OEMs of medical and sports and fitness equipment how easy it is to use EPIC technology.

The EPIC sensor is a new area of sensor technology that measures changes in an electric field in a similar way to a magnetometer detecting changes in a magnetic field.

The sensor, which requires no physical or resistive contact to make measurements, enables products to be made such as medical scanners that are simply held close to a patient’s chest to obtain a detailed ECG reading or safety and security devices that can ‘see’ through walls.

The sensor can be integrated on a chip with other features such as data converters, digital signal processing and wireless communications capability.

The technology works at normal room temperatures and functions as an ultrahigh, input impedance sensor that acts as a highly stable, extremely sensitive, contactless digital voltmeter to measure tiny changes in the electric field down to mV.

Most places on Earth have a vertical electric field of about 100 V per metre. The human body is mostly water and this interacts with the electric field.