Detailed explanation of multimeter range selection and measurement errors
Using a multimeter for measurement may introduce certain errors. Some of these errors are the maximum absolute errors allowed by the accuracy level of the instrument itself. Some are human errors caused by improper adjustment and use. By correctly understanding the characteristics of a multimeter and the causes of measurement errors, mastering the correct measurement techniques and methods, measurement errors can be reduced.
Human error in reading is one of the reasons that affect measurement accuracy. It is inevitable, but can be minimized as much as possible. Therefore, special attention should be paid to the following points during use: 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.
1. 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%... 1
(1) Using multimeters with different accuracies to measure the error generated by the same voltage
(2) The error caused by measuring the same voltage with different ranges of a multimeter
(3) The error caused by measuring two different voltages with the same range of a multimeter
