| 摘要 |
<p>The versatility is enhanced by using a sensor producing an output signal of DC voltage. A sensor unit (400) includes three electrodes: a transmission electrode (401), a reception electrode (402) and a shielding electrode (403). The shielding electrode (403) isolates the transmission electrode (401) from the reception electrode (402) in a high-frequency manner and is earthed normally. A high-frequency voltage is applied to the transmission electrode (401) from a high-frequency oscillation circuit (410). A high-frequency voltage corresponding to the magnitude of the capacitance between the two electrodes (401) and (403) is outputted from the reception electrode (402). The high-frequency voltage outputted from the reception electrode (402) is transformed into a DC voltage by a detection circuit (420). The presence/absence or amount of a substance is determined depending on the magnitude of the DC voltage produced by the detection circuit (420).</p> |
