The error caused by the multimeter measuring voltage
The measurement process of the digital multimeter converts the measured value into a DC voltage signal by the conversion circuit, and then converts the voltage analog quantity into a digital quantity by the analog/digital (A/D) converter, then counts through the electronic counter, and finally uses the digital measurement result displayed directly on the display.
The function of the multimeter to measure voltage, current and resistance is realized through the conversion circuit part, and the measurement of current and resistance is based on the measurement of voltage, that is to say, the digital multimeter is expanded on the basis of the digital DC voltmeter.
For example: There is a 10V standard voltage, and it is measured with two multimeters with 100V gear, 0.5 level and 15V level, 2.5 level. Which meter has the smallest measurement error?
The first meter test: the maximum absolute allowable error △X1=±0.5%×100V=±0.50V.
The second meter test: the maximum absolute allowable error △X2=±2.5%×l5V=±0.375V.
Comparing △X1 and △X2, it can be seen that although the accuracy of the first watch is higher than that of the second watch, the error produced by the measurement of the first watch is larger than the error produced by the measurement of the second watch. Therefore, it can be seen that when choosing a multimeter, the higher the accuracy, the better. With a multimeter with high accuracy, it is necessary to choose an appropriate range. Only by choosing the correct range can the potential accuracy of the multimeter be brought into play.
The A/D converter of the digital DC voltmeter converts the analog voltage quantity that changes continuously with time into a digital quantity, and then the digital quantity is counted by the electronic counter to obtain the measurement result, and then the measurement result is displayed by the decoding display circuit. The logic control circuit controls the coordinated work of the circuit, and completes the entire measurement process in sequence under the action of the clock.
