How to choose the gear range of a multimeter
The human reading error of a multimeter is one of the reasons that affects measurement accuracy. It is inevitable, but it can be minimized as much as possible. Therefore, special attention should be paid to the following points during use:
Before measurement, the multimeter should be placed horizontally and mechanically zeroed
When reading, keep your eyes perpendicular to the pointer
When measuring resistance, zero adjustment should be performed every time the gear is changed. When it cannot be adjusted to zero, a new battery needs to be replaced
When measuring resistance or high voltage, do not hold the metal part of the meter probe with your hands to avoid human resistance diversion, increase measurement errors, or electric shock
When measuring the resistance in an RC circuit, cut off the power supply in the circuit and discharge the stored electricity in the capacitor before proceeding 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 a 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 level for various gears such as DC voltage, current, AC voltage, current, etc. is based on their*
(1) The error caused by measuring the same voltage using a multimeter with different accuracies
For example, if there is a 10V standard voltage and two multimeters are used to measure it at 100V, 0.5 and 15V, and 2.5 levels, which one has the smallest measurement error?
Solution: From equation 1, it can be obtained that: * * block meter measurement: * large * * allowable error
△ X1=0.5% 100V=0.50V.
**Block meter measurement: * large * * allowable error
Δ X2=2.5% l5V=0.375V.
Comparing △ X1 and △ X2, it can be seen that although the accuracy of the * * block meter is higher than that of the * * block meter, the error generated by measuring with the * * block meter is greater than that generated by measuring with the * * block meter. Therefore, it can be seen that when selecting a multimeter, the higher the accuracy, the better. With a high accuracy multimeter, it is necessary to choose the appropriate range. Only by selecting the correct range can the potential accuracy of a multimeter be fully realized.
(2) The error caused by measuring the same voltage with different ranges of a multimeter
For example, the MF-30 multimeter has an accuracy level of 2.5. When measuring a 23V standard voltage in 100V and 25V gears, which gear has the smallest error?
Solution: 100V gear * large * * allowable error:
X (100)=2.5% 100V=2.5V.
25V gear * large * * allowable error: △ X (25)=2.5% 25V=0.625V. As can be seen from the above solution:
Measure the standard voltage of 23V using a 100V gear, and the reading on the multimeter is between 20.5V and 25.5V. Measure the standard voltage of 23V using a 25V gear, and the reading on the multimeter is between 22.375V-23.625V. From the above results, it can be seen that Δ X (100) is greater than Δ X (25), indicating that the error measured in 100V gear is much larger than that measured in 25V gear. Therefore, when measuring different voltages with a multimeter, the error generated by measuring with different ranges is not the same. When meeting the value of the measured signal, it is advisable to choose a gear with a smaller range as much as possible. This can improve the measurement accuracy.
