How a Multimeter Works

This article describes how the multimeter works
working principle
The basic principle of the multimeter is to use a sensitive magnetoelectric DC ammeter (microammeter) as the head. When a tiny current passes through the meter, there will be a current indication. However, the meter head cannot pass a large current, so some resistors must be connected in parallel or in series on the meter head for shunt or step-down, so as to measure the current, voltage and resistance in the circuit.
design principle
The measurement process of the digital multimeter is converted into a DC voltage signal by the conversion circuit, and then the analog-to-digital converter converts the voltage analog into a digital quantity, and then counts through an electronic counter, and the measurement results are directly displayed on the display screen. .
The function of measuring voltage, current and resistance of the multimeter is realized by the conversion circuit part, and the measurement of current and resistance is based on the measurement of voltage, that is to say, the digital multimeter is extended on the basis of the digital DC voltmeter.
The digital DC voltmeter A/D converter converts the analog voltage that changes continuously with time into a digital quantity, and then counts the digital quantity by an electronic counter to obtain the measurement result, and then the decoding display circuit displays the measurement result. The logic control circuit controls the coordinated work of the circuit, and completes the entire measurement process in sequence under the action of the clock.
Common type
A digital multimeter is a commonly used digital instrument. Its main features are high accuracy,
Strong resolution, perfect test function, fast measurement speed, intuitive display, strong filtering ability, low power consumption, and easy to carry. Since the 1990s, digital multimeters have been rapidly popularized and widely used, and have become an essential instrument for modern electronic measurement and maintenance work, and are gradually replacing traditional analog multimeters.
Digital multimeters, also known as digital multimeters, come in many varieties and models. Every electronics worker wants to have an ideal digital multimeter. There are many principles for choosing a digital multimeter, and sometimes it varies from person to person. But for a handheld digital multimeter, it should have the following characteristics: clear display, high accuracy, strong resolution, wide test range, complete test functions, strong anti-interference ability, relatively complete protection circuit, beautiful appearance, generous, easy to operate Simple, flexible, reliable, low power consumption, easy to carry, affordable and so on.
Main indicators, display digits and display characteristics of digital multimeter.
The display digits of digital multimeters are usually 3 1/2 digits to 8 1/2 digits. There are two principles for judging the display digits of a digital instrument: one is that the digits that can display all digits from 0 to 9 are integer digits; At full scale, the count value is 2000, which means that the meter has 3 integer digits, and the numerator of the fractional digit is 1, and the denominator is 2, so it is called 3 1/2 digits, read as "three and a half", only Displays 0 or 1. The 3 2/3-digit multimeter can only display numbers from 0 to 2, and the displayed value is ±2999. Under the same conditions, it is 50% higher than the limit of 3 1/2 digit digital multimeter, especially in measuring 380V AC voltage is very valuable.