Plessey Semiconductors has designed a heart rate monitor demonstration using its EPIC sensor technology, which is the same size as a wristwatch and does not require a chest strap or second sensor at the end of a cable that could be easily lost or damaged. This reference design shows that simple and effective personal monitoring of electrocardiograph (ECG) signals can be as easy as taking a pulse measurement. The device straps to the wrist with a sensor electrode on the rear of the device in permanent contact with the wrist and the second electrode is on the front of the device. Touching this top electrode with a finger from the opposite hand enables the device to collect the heart signals.
“Our EPIC technology really makes heart monitoring so much simpler,” explained Plessey’s EPIC Programme Director, Dr Paul James. “Just two small contacts and no gels. This is ideal for the Sports and Fitness market where people want to measure more than just their heart rate when exercising for display either on the device or via a Bluetooth link to a mobile phone, tablet or PC. The data gathered is accurate enough that it can 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.”
Plessey 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 such 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 EPIC sensor is a completely 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. It requires no physical or resistive contact to make measurements. 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 ultra-high, input impedance sensor that acts as a highly stable, extremely sensitive, contactless digital voltmeter to measure tiny changes in the electric field down to milliVolts. Most places on Earth have a vertical electric field of about 100 Volts per metre. The human body is mostly water and this interacts with the electric field. EPIC technology is so sensitive that it can detect these changes at a distance and even through a solid wall.