Analysis of Measurement Error and Selection of Multimeter Range
There will be some errors when measuring with a multimeter. Some of these errors are the maximum absolute errors allowed by the accuracy class of the meter itself. Some are human errors caused by adjustment and improper use. Correctly understand the characteristics of the multimeter and the causes of measurement errors, and master the correct measurement techniques and methods, you can reduce the measurement errors.
Human reading error is one of the reasons that affect the measurement accuracy. It is unavoidable but can be minimized. Therefore, special attention should be paid to the following points during use: 1. Place the multimeter horizontally before measuring, and perform mechanical zeroing; 2. Keep your eyes perpendicular to the pointer when reading; When the adjustment is less than zero, replace the battery with a new one; 4. When measuring resistance or high voltage, do not hold the metal part of the test lead with your hands, so as to avoid shunting of human body resistance, increasing measurement error or electric shock; 5. When measuring the resistance in the RC circuit, you must Cut off the power supply in the circuit, and discharge the electricity stored in the capacitor before measuring. After excluding the human-made reading errors, we conduct some analysis on other errors.
1. Multimeter Voltage, Current Range Selection and Measurement Error
The accuracy level of the multimeter is generally divided into several levels such as 0.1, 0.5, 1.5, 2.5, and 5. For DC voltage, current, AC voltage, current and other gears, the calibration of the accuracy (accuracy) level is expressed by the percentage of the maximum absolute allowable error △X and the full scale value of the selected range. Expressed by formula: A%=(△X/full scale value)×100%... 1
2. Range selection and measurement error of electrical barrier
Each range of electrical resistance can measure the resistance value from 0 to ∞. The scale scale of an ohmmeter is a non-linear, uneven, inverted scale. It is expressed as a percentage of the arc length of the scale. Moreover, the internal resistance of each range is equal to the multiplier of the central scale number of the arc length of the scale, which is called "central resistance". That is to say, when the measured resistance is equal to the center resistance of the selected range, the current flowing in the circuit is half of the full scale current. The pointer indicates the center of the scale.
