| 摘要 |
PURPOSE:To provide a measuring device by which a bias current or an input impedance of an input amplifier will not be errors of measurement even when an input amplifier of normal function is used. CONSTITUTION:A measuring device comprises an input amplifier 11 in which a bias current in an input terminal is Ia and an input impedance is Ra, an AD converter 10 for converting an output signal of the input amplifier 11 into a digital signal, two resistances R, (r), which have known resistance values that are different from one another, and the one ends of which are connected to a common electric potential, a resistance RP, the one end of which is connected to a measurement terminal 17, and a first switching means SWa for choosing and leading the other ends of the three resistances to the input terminal of the input amplifier. Series circuits of a constant current source IS connected between the measurement terminal 17 and the common electric potential, and of a second switch means SWS, a muP15 for leading the output signal of the AD converter, controlling the switching of the two switch means, and for calculating the value of an inner voltage VO of a signal formation source 21, are also provided. |
