| 摘要 |
PURPOSE:To attain switching operation at a high speed and, at the same time, to miniaturize a multi-point resistance measuring device, by making an electric current to flow from a current source through a switch and diode connected with a common electric potential section and introducing a voltage to a detecting circuit through the switch. CONSTITUTION:When switches Sna, Snb, and Snc are set to closed conditions by means of a driving device 10, output voltage V0 of a differential amplifier 2 becomes V0= -{[Ia(Xn+Rna)-IbRnb]+(U1-U2) }. The Xn of the formula is the electric resistance of a resistor 9, Rna and Rnb are electric resistances of conductors Lna and Lnb, and U1 and U2 are voltage drops at switches Sna and Snb under the closed condition. Since the electric currents under this condition are set to become a constant current I (I=Ia=Ib) and the resistances Rna and Rnb are set to Rna=Rnb and, therefore, little current flows to the switches Sna and Snb, the voltage drop at the switches Sna and Snb becomes U1 0 and U2 0. Accordingly, the output voltage of the amplifier 2 becomes V0=-IXn and the electric resistance of the resistor 9 can be measured irrespectively of the electric resistance of the conductors and closed switches. Resistors 7 and 8 can also be measured in the same manner.
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