| 摘要 |
<p>PURPOSE:To execute highly-precise calibration in a short time by executing calibration of each range by using a calibration voltage source provided inside an apparatus. CONSTITUTION:A standard voltage of a standard battery 22 is given directly to an A/D converter 15, and a calibration coefficient for modifying an A/D conversion value thereof to a value corresponding to the standard voltage is determined and stored in a memory 18. This converter 15 being used, a calibration voltage of a calibration voltage source 23 provided inside is measured and a true value Vr of the calibration voltage is determined. Next, in the state wherein a resistor R1 of the smallest resistance value out of a plurality of resistors for detection of current is connected between the input and output terminals of an operational amplifier 11, a standard current source 24 is connected to the input terminal of the amplifier 11, so as to determine a true resistance value R1. Then, a resistor R2 (to R4) for detection is connected between the amplifier 11 and the voltage source 23 and a current is give to the resistor R1 through the resistor R2 (to R4). A resistance value R2 (to R4) of a resistor R2 is measured from a voltage generated in this state, and a calibration coefficient for modifying the divergence thereof is determined by computation by a microcomputer 17.</p> |
