engleski

Determination of High-Resolution Digital Voltmeter Input Parameters

High resolution digital voltmeter can be widely used when precise measurements are needed, but input circuitry can contribute to the results of measurement. Therefore, to make uncertainty of measurement as small as possible for a particular measurement, it is necessary to characterize its input parameters. In this paper the methods for the determination of input resistance, capacitance and input offset current of the precise digital voltmeters HP 3458A with 8½ ; digits resolution are presented. The method with voltage source and high-ohmic divider resistor has been developed for the determination both the input offset current IS, as well as the input resistance RV. The second method with source of linear voltage ramp and picoampermeter is primary used for the determination of input capacitance CV. It was shown that: input offset current of voltmeters is in the range of picoamperes, with relative instability of approximately +/-0.1 ; input resistance is in the range of teraohm with the same relative instability of +/-0.1 ; and the input capacitance was measured to be in the range of few hundred picofarads with an uncertainty of a few picofarads.

Digital voltmeter (DVM); input capacitance; input offset current; input resistance

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