Analysis of the error in the measurement of different voltages with the same range of multimeters
A multimeter consists of three main parts: the meter head, the measurement circuit and the changeover switch.
Multimeter is the most basic tool in the field of electronic testing and a widely used testing instrument. Multimeter is also known as multi-meter, triple meter (A, V, Ω that is, current, voltage, resistance, three), multiplexing meter, multimeter, multimeter is divided into pointer multimeter and digital multimeter, there is also an oscilloscope with oscilloscope function of the oscilloscope multimeter, is a kind of multifunctional, multi-range measurement instrument. General multimeter can measure DC current, DC voltage, AC voltage, resistance and audio level, etc. Some can also measure AC current, capacitance, inductance, temperature and semiconductor (diode, transistor) of some parameters. Digital multimeter has become the mainstream, has replaced the analogue meter. Compared with analogue meters, digital meters have high sensitivity, high accuracy, clear display, strong overload capacity, easy to carry, and more convenient and simple to use.
With a multimeter of the same range to measure different two voltages produced by the error
For example: MF-30 type multimeter, its accuracy is 2.5 level, with 100V block to measure a 20V and 80V standard voltage, ask which block error is small?
Maximum relative error: △ A% = maximum absolute error △ X / measured standard voltage regulation × 100%, 100V block of the maximum absolute error △ X (100) = ± 2.5% × 100V = ± 2.5V.
For 20V, its display value is between 17.5V-22.5V. The maximum relative error is: A (20)% = (±2.5V/20V) × 100% = ±12.5%.
For 80V, its display value is between 77.5V-82.5V. The maximum relative error is: A(80)% =±(2.5V/80V)×100%=±3.1%.
Comparison Comparing the maximum relative error of the measured voltage 20V and 80V, it can be seen: the former is much larger than the latter error. Therefore, when measuring two different voltages with the same range of a multimeter, whoever is closer to the full stop value will have higher accuracy. Therefore, when measuring voltage, the measured voltage should be made to indicate more than 2/3 of the multimeter range. Only in this way can the measurement error be reduced.
The basic principle of the multimeter is to use a sensitive magneto-electric DC ammeter (microammeter) to make the meter head.
When a small current passes through the meter head, there will be a current indication. However, the head cannot pass large currents, so some resistors must be connected in parallel and series on the head to shunt or step down the voltage, so as to measure the current, voltage and resistance in the circuit.
