Analysis of Measurement Error of Digital Multimeter
1. Multimeter range selection and error analysis
1.1. Human error
Man-made reading error is one of the reasons that affect the measurement accuracy, special attention should be paid to the following points during use
(1) Place the multimeter horizontally before measuring, and perform mechanical zero adjustment
(2) Keep your eyes perpendicular to the pointer when reading
(3) When measuring resistance, zero adjustment must be performed every time the gear is changed, and a new battery should be replaced when the adjustment is less than zero, and the metal part of the test lead should not be pinched by hand, so as to avoid shunting of human body resistance and increase measurement error
(4) When measuring the resistance in the circuit, the power supply in the circuit should be cut off, and the capacitor should be fully discharged before measuring.
1.2. Multimeter voltage and current range selection and measurement error
The accuracy grades of multimeters are generally divided into 0.1, 0.5, 1.5, 2.5, 5, etc. For DC voltage, current and AC voltage, current, etc., the calibration of the accuracy level is expressed by the percentage of the maximum absolute allowable error △x and the full scale value of the selected range.
The error produced by a multimeter measuring voltage is different from the error produced by using a multimeter with different accuracy to measure the same voltage. When choosing a multimeter, the higher the accuracy, the better. With a multimeter with high accuracy, it is necessary to select an appropriate range to maximize the potential accuracy of the multimeter. The errors produced by measuring the same voltage with different ranges of a multimeter are also different. In the case of satisfying the value of the measured signal, you should try to choose a file with a small range, which can improve the accuracy of the measurement. Therefore, when measuring the voltage, the measured voltage should be indicated above 2/3 of the multimeter's range, so as to reduce the measurement error.
1.3. Range selection and measurement error of resistance gear
When using a multimeter to measure the same resistance, the errors generated by selecting different ranges are different, and the errors generated by the measurement are very different. When selecting the gear range, try to make the measured resistance value in the center of the arc length of the range scale, and the measurement accuracy will be higher.
