Introduction to the 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, and 5. For each gear of DC voltage, current, AC voltage, current, etc., the calibration of the accuracy (precision) grade is expressed as the percentage of the maximum absolute allowable error △X to the full-scale value of the selected range. Expressed by the formula: A% = (△X / full-scale value) × 100%.
The 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 the 100V gear and the 25V gear are selected to measure a standard voltage of 23V, which gear has a smaller error?
The maximum absolute allowable error of the 100V gear: X(100) = ±2.5% × 100V = ±2.5V.
The maximum absolute allowable error of the 25V gear: △X(25) = ±2.5% × 25V = ±0.625V.
It can be seen from the above: When measuring the 23V standard voltage with the 100V gear, the indication value on the multimeter is between 20.5V and 25.5V. When measuring the 23V standard voltage with the 25V gear, the indication value on the multimeter is between 22.375V and 23.625V. From the above results, △X(100) is greater than △X(25), that is, the error of measuring with the 100V gear is much larger than that of measuring with the 25V gear. 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 gear with a smaller range 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. Even some multimeters can 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 multifunctional measuring instrument with a meter head as the core component, and the measured value is read by 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 also have a voice prompt function. A multimeter uses a common meter head and is an instrument that integrates a voltmeter, an ammeter, and an ohmmeter.
