Errors arising from voltage measurements with multimeters
The measurement process of the digital multimeter consists of a conversion circuit to convert the measured DC voltage signal, then an analogue/digital (A/D) converter to convert the voltage analogue to digital, then counting through an electronic counter, and finally displaying the measurement result in digital directly on the display.
Multimeter measurement of voltage, current and resistance function is partially achieved through the conversion circuit, while the current, resistance measurement are based on the measurement of voltage, that is to say, the digital multimeter is in the digital DC voltmeter on the basis of the expansion into.
For example: there is a 10V standard voltage, with 100V block, 0.5 level and 15V block, 2.5 level of the two multimeter measurements, ask which table measurement error is small?
The first meter measures: the maximum absolute permissible error △X1 = ±0.5% × 100V = ±0.50V.
The second meter measurement: the maximum absolute permissible error △ X2 = ± 2.5% × l5V = ± 0.375V.
Comparison of △ X1 and △ X2 can be seen: although the first table accuracy is higher than the second table accuracy, but with the first table to measure the error generated than the second table to measure the error generated by the larger. Therefore, it can be seen that in the choice of multimeter, not the higher the accuracy the better. With a high degree of accuracy of the multimeter, but also to choose the appropriate range. Only the correct choice of range, in order to play the potential accuracy of the multimeter.
Digital DC voltmeter A/D converter will continuously change over time analogue voltage quantity into digital quantity, and then by the electronic counter on the digital quantity counting to get the measurement results, and then by the decoding display circuit will be measured results displayed. Logic control circuit to control the coordinated work of the circuit, under the action of the clock in order to complete the entire measurement process.
