We describe the recording
of human heart and movement related biopotentials remotely from a subject in an
open space. A new low-cost, low-noise, displacement current based sensor has
been developed and used to record heart related biopotentials at distances up
to 40 cm from the surface of the body, and movement related biopotentials at
distances up to 10 m from the body. The sensor is built around a simple transimpedance
amplifier circuit which utilises a resistive feedback T-network to eliminate
the need for ultra high values resistors normally needed in amplifiers for this
type of measurements. The sensor provides an operational
bandwidth of 0.5 – 250 Hz, and a noise level of 7.8mV/ÖHz at 1 Hz down to 30nV/ÖHz at 1 kHz. Reported results,
which were all obtained in normal unshielded environments, demonstrate the
sensor’s remarkable capability in remotely recording a wide range of human body
electrical signals.