Patent ID: 8340748

Claim:
A fetus electrocardiogram signal measuring method for measuring, in an on-line manner, fetus electrocardiogram waveforms from a plurality of electrodes for attachment to a breast and an abdomen of a mother's body during pregnancy, the method comprising the steps of: (a) providing a high input impedance electrode section having an impedance of 100 GΩ or above for directly acquiring biological information, the high input impedance electrode section comprising: a skin contact electrode section composed of a plurality of measurement electrodes and a reference electrode, each electrode being a high input impedance electrode of an impedance of 100 GΩ or above; a preamplification section having a characteristic of a high input impedance of 100 GΩ or above; and a shield cable, (b) providing a region-variable ground electrode section for addressing various positional variations of the fetus, the region-variable ground electrode section being constituted of one or more region-variable ground electrodes; (c) providing a differential amplification section serving as a main measuring member and having a differential characteristic; and (d) providing an electrode optimization computing section that selects an optimal ground electrode region and an optimal electrode out of combinations of all of the electrodes, in order to optimally control the fetus position/state so that a maximum signal with low noise can be measured, wherein the preamplification section is a preamplifier including an operational amplifier located between the differential amplification section and an electrode measurement point; and wherein the preamplification section reduces a bias current flowing from the region-variable ground electrode section to the differential amplification section down to a current on an order of picoamperes, and performs a potential difference measurement with a high sensitivity better than ±1 μV.