The error problem of measuring the same voltage with different ranges of the multimeter
Take a MF-30 multimeter as an example, its accuracy is 2.5 grades, choose 100V gear and 25V gear to measure a 23V standard voltage, which gear should be selected will have a smaller error.
1. The maximum absolute allowable error for 100V gear: X(100)=±2.5%×100V=±2.5V.
2. The maximum absolute allowable error for 25V gear: △X(25)=±2.5%×25V=±0.625V.
Measurement error analysis:
Use the 100V block to measure the 23V standard voltage, and the indication on the multimeter is between 20.5V-25.5V. Use the 25V block to measure the 23V standard voltage, and the indication value on the multimeter is between 22.375V-23.625V.
It can be seen that △X(100) is greater than △X(25), that is, the error of 100V block measurement is much larger than that of 25V block measurement.
Summary: When using a multimeter to measure different voltages, the errors generated by different ranges are different. In the case of satisfying the value of the signal to be measured, the gear with the smallest range should be selected as much as possible, which can improve the accuracy of the measurement.
The error of the multimeter measuring different voltages in the same range
Take a MF-30 multimeter as an example, its accuracy is 2.5, measure a standard voltage of 20V and 80V with the 100V gear, choose which gear has the smallest error.
Measurement error analysis:
1. The maximum relative error: △A%=maximum absolute error △X/measured standard voltage adjustment×100%, the maximum absolute error of 100V gear △X(100)=±2.5%×100V=±2.5V.
2. At 20V, the indication value is between 17.5V-22.5V. The maximum relative error is: A(20)%=(±2.5V/20V)×100%=±12.5%.
3. At 80V, the indication value is between 77.5V-82.5V. The maximum relative error is: A(80)%=±(2.5V/80V)×100%=±3.1%.
Comparing the maximum relative error of the measured voltage 20V and 80V, it will be found that the error of the former is much larger than that of the latter.
Summary: Use the same range of a multimeter to measure two different voltages, the closer to the full scale value, the higher the accuracy. When measuring voltage, the measured voltage indication should be more than 2/3 of the range of the multimeter to reduce the measurement error.
The above analyzes the error problem of the multimeter measuring different voltages. The selection of gears is different when measuring the same voltage with different ranges of the multimeter, and measuring different voltages with the same range of the multimeter.
