Error in the measurement of the voltage with a multimeter
The measurement process of a digital multimeter is converted into a DC voltage signal by a conversion circuit, and then the voltage analog signal is converted into a digital signal by an analog-to-digital (A/D) converter. Then, it is counted by an electronic counter, and finally the measurement result is displayed directly on the display screen in digital form.
The function of measuring voltage, current, and resistance with a multimeter is achieved through the conversion circuit, while the measurement of current and resistance is based on voltage measurement. In other words, a digital multimeter is an extension of a digital DC voltmeter.
For example, if there is a 10V standard voltage and two multimeters with 100V gear, 0.5 level and 15V gear, and 2.5 level are used for measurement, which one has the smallest measurement error?
The first measurement: maximum absolute allowable error △ X1=± 0.5% × 100V=± 0.50V.
Second measurement: 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 meter is higher than that of the second meter, the error generated by measuring with the first meter is larger than that generated by measuring with the second meter. Therefore, it can be seen that when choosing a multimeter, higher accuracy is not necessarily better. With a highly accurate multimeter, it is also necessary to choose a suitable range. Only by selecting the correct range can the potential accuracy of a multimeter be fully utilized.
The A/D converter of the digital DC voltmeter converts the continuously changing analog voltage into a digital value, which is then counted by an electronic counter to obtain the measurement result. The decoding display circuit then displays the measurement result. The logic control circuit coordinates the operation of the control circuit and completes the entire measurement process in sequence under the action of the clock.
