Noncontact human electrophysiological measurements using a new displacement current sensor

摘要

In this paper we describe a newly developed displacement current sensor for non-contact, non-invasive human electrophysiological measurements, well suited for applications requiring remote detection of human presence. The sensor is built around an improvised transimpedance amplifier circuit, which employs a resistive feedback T-network to eliminate the need for ultra high values resistors normally needed for this type of measurements. It provides an operational bandwidth of 0.5–250 Hz and a remarkable noise floor of 7.8 µV/√Hz at 1Hz down to 30 nV/√Hz at 1 kHz. The sensor is particularly suitable for non-contact measurement of human electrophysiological signals, such as the ECG. Reported results, all obtained in normal unshielded environment, demonstrate the sensor''s capability in measuring human heart related electrophysiological signals at off-body distance up to 50 cm. Two different sensor configurations are presented; a single-ended signal measurement using one sensor, and a differential signal measurement using two sensors.