A multimeter is an important electronic device that is constructed with the help of passive and active electronic components in order to measure electrical parameters. Generally, it is of two types- analog and digital multimeter. There is not much difference in their working except that they have different constructions.
An analog one represents the desired output with the help of a needle directed along a scale, just like the speedometer in our bikes. The scale is calibrated as per the design specifications and the needle points at the required output.
The digital one displays the output digitally. For instance, consider your digital watch that shows you the time in exact numbers. Similarly, digital mutimeters display the output in numbers.
You need not bother yourself with the number of divisions in the scale or the calibration of the instrument like in the case of an analog multimeter. This makes digital multimeter a better option than analog multimeter, as the chances of making a mistake in taking a correct reading decreases to a large extent.
All you need is to connect the probes and take the reading. The digital mulitmeters are provided with liquid crystal display (LCD) screen or light emitting diodes (LED) that display the numbers. We all know that an ammeter is used for measuring current, a voltmeter for measuring voltage and ohmmeter is used for measuring resistance.
A digital multimeter, whereas can be used to solve all these purposes. With this single device, you can measure all the parameters. It lets you measure these and many more parameters just on a single instrument.
Measuring Electrical Parameters
To measure the resistance of a wire, generally we use the color coding method. Most of the resistors have a four color band type. Carefully observe the structure of your digital multimeter. Usually you will find a knob at its center. This knob can be rotated (similar to the knobs in our fan regulators) and adjusted for the measurement of various parameters.
The scale of the multimeter is divided into various voltage, current and resistance measurement ranges. The symbol V stands for voltage, symbol Ω for resistance and symbol I for current on the multimeter. Just switch over the knob to the position for which you require to take the measurement.
In a multimeter there are two probes, red and black in color, that are considered to be the positive and negative terminals of the multimeter respectively. Basically, the black lead is always connected to the socket that is marked as COM meaning common. The red lead is connected to socket that is marked as V(voltage).
To measure the resistance place your knob in the resistance range. Resistance is measured in ohms that is represented by the Greek letter Ω (Omega). Take the two probes and touch the ends of the resistor for which you wish to determine the resistance.
The multimeter will immediately give you the resistance of the wire. You can cross check the resistance of the wire by measuring the resistance by the color code method.
Similarly, we can measure the alternating/direct current (AC/DC) and check for the continuity of a circuit. A diode shows zero resistance in the forward biased condition, and infinite resistance in the reverse biased direction. You can use a multimeter to check if the diode is working properly.
You can use it similarly for other electronic components too. This will connect the diode in forward bias mode. When you reverse the polarities, the diode will get connected in reverse bias mode and it will show infinite resistance. This way, it can be used to test the working of a diode.
One should always ensure that the safety precautions are not ignored. The only thing we should take care is to put the knob in the range of the respective parameter that is being measured. Take proper care while handling the electronic equipment and do not directly connect it to any power supply without the supervision of a guide or teacher.