How to select a multimeter range and avoid measurement errors
There will be certain errors when measuring with a multimeter. Some of these errors are the maximum errors allowed by the accuracy level of the instrument itself. Some are human errors caused by improper adjustment and use. If you correctly understand the characteristics of multimeters and the causes of measurement errors, and master the correct measurement techniques and methods, you can reduce measurement errors.
Human reading error is one of the factors affecting measurement accuracy. It is unavoidable but can be minimized. Therefore, special attention should be paid to the following points during use:
1. Before measurement, place the multimeter horizontally 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 you change gears. If it cannot reach 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 to avoid shunting of human body resistance, increasing measurement error or causing electric shock;
5. When measuring the resistance in an RC circuit, cut off the power supply in the circuit and discharge all the electricity stored in the capacitor before measuring again. After excluding human reading errors, we conduct some analysis on other errors.
Multimeter voltage and current range selection and measurement error
The accuracy levels of multimeters are generally divided into several levels such as 0.1, 0.5, 1.5, 2.5, 5, etc. For DC voltage, current, AC voltage, current and other gears, the calibration of accuracy (precision) level is represented by the percentage of the maximum allowable accuracy error △X and the full scale value of the selected range. Expressed by the formula: A%=(△X/full scale value)×100%……1
2. Range selection and measurement error of electrical barrier
Each range of electrical resistance can measure resistance values from 0 to ∞. The scale of the ohmmeter is a non-linear, uneven inverted scale. It is expressed as a percentage of the arc length of the ruler. Moreover, the internal resistance of each range is equal to the central scale number multiplied by the arc length of the ruler, which is called the "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 is in the center of the scale.
