Error Analysis of Measuring the Same Voltage with Different Ranges of a Multimeter
The accuracy grades of a multimeter are generally divided into several levels such as 0.1, 0.5, 1.5, 2.5, 5, etc. For each range of DC voltage, DC current, AC voltage, AC current, etc., the calibration of the accuracy (precision) grade is expressed as the percentage of the maximum allowable absolute error △X to the full-scale value of the selected range. Expressed by the formula: A% = (△X / full-scale value) × 100%.
Errors generated when measuring the same voltage with different ranges of a multimeter.
For example, for an MF-30 multimeter with an accuracy of grade 2.5, when using the 100V range and the 25V range to measure a standard voltage of 23V, which range has a smaller error?
The maximum allowable absolute error of the 100V range: X(100) = ±2.5% × 100V = ±2.5V.
The maximum allowable absolute error of the 25V range: △X(25) = ±2.5% × 25V = ±0.625V.
As can be seen from the above: when measuring the standard voltage of 23V with the 100V range, the indication value on the multimeter is between 20.5V and 25.5V. When measuring the standard voltage of 23V with the 25V range, the indication value on the multimeter is between 22.375V and 23.625V. From the above results, △X(100) is much larger than △X(25), that is, the error of measurement with the 100V range is much larger than that with the 25V range. Therefore, when a multimeter measures different voltages, the errors generated by measuring with different ranges are different. When the value of the measured signal is satisfied, the range with a smaller value should be selected as much as possible. In this way, the measurement accuracy can be improved.
A multimeter can not only be used to measure the resistance of the measured object, but also the AC and DC voltages. Some multimeters can even measure the main parameters of transistors and the capacitance of capacitors, etc. Mastering the usage method of a multimeter proficiently is one of the most basic skills in electronic technology. Common multimeters include pointer multimeters and digital multimeters. A pointer multimeter is a multi-functional measuring instrument with a meter head as the core component, and the measured value is read according to the indication of the meter head pointer. The measured value of a digital multimeter is directly displayed in digital form on the liquid crystal display screen, which is convenient to read, and some even have a voice prompt function. A multimeter shares one meter head and is an instrument integrating a voltmeter, an ammeter and an ohmmeter.
