Detailed explanation of selecting a multimeter range and measuring error
1. Before measurement, the multimeter should be placed horizontally and mechanically zeroed;
2. When reading, keep your eyes perpendicular to the pointer;
3. When measuring resistance, it is necessary to zero it every time the gear is changed. If it cannot be adjusted to zero, a new battery should be replaced;
4. When measuring resistance or high voltage, do not hold the metal part of the probe with your hand to avoid human resistance shunt, increase measurement error or electric shock;
5. When measuring the resistance in an RC circuit, it is necessary to cut off the power supply in the circuit, discharge the stored electricity in the capacitor, and then proceed with the measurement. After excluding human reading errors, we conducted some analysis on other errors.
Selection and measurement error of voltage and current range for multimeter
The accuracy level of a multimeter is generally divided into several levels such as 0.1, 0.5, 1.5, 2.5, and 5. The calibration of accuracy (precision) levels for DC voltage, current, AC voltage, current, and other gears is expressed as the percentage of the maximum absolute allowable error △ X to the selected full-scale value of the range. Expressed in formula: A%=(△ X/full-scale value) × 100%
The error caused by measuring the same voltage with different ranges of a multimeter
Measure the 23V standard voltage with 100V gear, and the reading on the multimeter is between 20.5V and 25.5V. Measure the 23V standard voltage with the 25V gear, and the reading on the multimeter is between 22.375V and 23.625V. From the above results, it can be seen that △ X (100) is greater than △ X (25), indicating that the measurement error at 100V gear is much larger than that at 25V gear. Therefore, when measuring different voltages with a multimeter, the errors generated by measuring with different ranges are not the same. When meeting the values of the measured signal, it is advisable to choose gears with smaller ranges as much as possible. This can improve the accuracy of the measurement.
(3) The error caused by measuring two different voltages with the same range of a multimeter
Comparing the maximum relative error between the measured voltage of 20V and 80V, it can be seen that the former has a much larger error than the latter. Therefore, when measuring two different voltages with the same range of a multimeter, whoever is closer to the full range value has higher accuracy. Therefore, when measuring voltage, the measured voltage should be indicated at 2/3 or more of the multimeter range. Only in this way can measurement errors be reduced.
