Researchers from the University of Sussex are developing a heartbeat sensor that works without electrical connections to the patient, unlike current electro-cardiograms (ECGs).
The team has already created a device that monitored the heartbeat of a fully clothed person from a metre away.
Terry Clark, an electrical engineer at the University, said: "The problem with ECGs is that the skin contacts distort the electrical measurements because they drain the current slightly. So you get a smaller and distorted signal. It's best not to make skin contact."
The team's device measures displacement current, which is a measure of the changing electric field in the air, generated by the shifting voltages on the skin surface.
To measure this subtle current in the air without shorting it, a sensor with higher impedance than that of the air gap between the body and the sensor is needed. Otherwise, the sensor drains the electrical signal just like an ECG contact sensor does.
The sensor itself is a small copper disc about 1cm across. The team used a number of electronic feedback techniques to make its impedance 100 times higher than that of air.
Potential applications for the sensor include remote monitoring of burn victims who cannot be touched.
