Frequency-response-based analysis of respiratory sensor measuring capacitance built across skin

Abstract

A capacitive respiratory sensor is studied by attaching the electrodes to the skin. The signal characteristics related to the electrode position and body motion are examined. The frequency response indicates the nearly pure capacitance characteristics. The sensing mechanism model based on the equivalent skin thickness change generated by the body volume change accompanying respiration is reasonably consistent with the experimental results. The sensing method is examined by measuring the frequency response under some different conditions including the grounding issue. The electrode attached to the concave site tends to show a smaller signal difference between inhalation and exhalation. The convex site stabilizes the measurement. The bellyband combined with the electrode realizes stable sensing with comfortable fit on the skin.

Respiration monitoring during 6 min walk using wearable sensor measuring capacitance built across skin

“…The electrical field does not run perpendicular to the electrode surface and the fringe field is considered to be major. 23) The area of 35 × 35 mm 2 still gives a reasonable dependence on the area. For combining with the magnet connector, an electrode width larger than the connector size (10 mm) is necessary.…”

“…The electrodes of the conductive cloths are sewn inside the belly band, since the belly band assists in fitting the electrode to the skin. 23) The noise comes from both the outside and the inside of the body. Figure 3 shows three connections tested between the electrode and the cable to the capacitance sensor.…”

“…The capacitance is constructed between one outside electrode attached on the skin and another as the electrolyte inside, which is the conductive body fluid. 23) The interior of the human body is considered to be a conductive electrolytic solution, and its resistance will be small. Figure 1(b) shows the conditions under inhalation at the abdomen.…”

Towards prevention and prediction of infectious diseases with virus sterilization using ultraviolet light and low-temperature plasma and bio-sensing devices for health and hygiene care

“…Sasaki and colleagues developed a wearable respiration sensor for noninvasive vital sign monitoring. [138][139][140] They put conductive textile electrodes on the abdomen and back of a subject and measured the electrical capacitance formed around the human body. Respiration induces skin contraction and expansion, resulting in capacitance change.…”