A multimeter is an electrical measuring instrument used to measure electrical parameters such as voltage, current, and resistance. Not all multimeters are the same. Different multimeters are different in size, precision, accuracy, and measurement parameters. Multimeters are mainly used by electricians, engineering students, and amateurs to troubleshoot electrical equipment and circuits.
There are two main types of multimeters, namely analog multimeters and digital multimeters.
The analog multimeter is the oldest multimeter. It has a needle that rotates along the scale, but it is difficult to read. The advantage is that it is cheap and sensitive. Analog multimeters are more sensitive than digital multimeters and can even sense small changes in readings.
The analog multimeter is made of a coil placed between two permanent magnets, and a needle is placed on top of the coil.
When current passes through the coil, the coil generates a magnetic field that interacts with the magnetic field of the permanent magnet, thereby rotating. As the coil rotates, the pointer moves along the scale. The rotation angle of the coil depends on the amount of current flowing through the coil.
Therefore, an analog multimeter is also called a galvanometer, and its resistance is very small, so it is more sensitive than a digital multimeter.
But be careful to avoid full-scale deflection (FSD). When the current exceeds the deflection range of the coil, it starts to burn the coil, causing damage to the meter.
A digital multimeter refers to a meter that can measure various parameters and display them on the LCD screen. Different from analog multimeters, digital multimeters are displayed in the digital calculation, so it is easier to read the measurement results. But the other side of this advantage is that the analog multimeter can display readings without any calculations, so it has a fast response time.
The digital multimeter has an LCD, a rotating dial, and multiple ports. The dial includes an internal circuit that is connected by a ring of concentric rings. The dial knob is used to activate the circuit to take a specific measurement.
A microprocessor is embedded in the digital multimeter to calculate the readings. However, the input voltage or current is in analog form. Therefore, an ADC (Analog-to-Digital Converter) is included to convert the readings and display them on the LCD screen. Unlike the pointer scale on an analog multimeter, the LCD makes the measurement results easy to read.
In addition, when the measurement is out of range, the digital multimeter has overload protection.