Understanding multimeters: how to use them?

Thread Content

How to use a multimeter? This is a small challenge for many novice electricians or home users who own a multimeter but don’t know how to use it. Today we’ll talk about the functions of a multimeter. It is an essential measuring instrument for electricians, primarily used for measuring voltage, current, and resistance. Multimeters are classified into analog multimeters and digital multimeters based on their display method. It is a multi-functional, multi-range measuring instrument, also known as a three-in-one meter or multimeter. Since digital multimeters are more precise, more intuitive, and simpler, emphasis is placed on digital multimeters. However, analog multimeters do have advantages over digital multimeters in circuit board repair; each type has its own strengths. Digital multimeter, user-friendly. Suitable for beginners: 1: Before making measurements, ensure that the multimeter is in good condition and gives accurate readings. The test leads are in good condition. The accessories are in good condition. Especially when measuring high voltages, it is necessary to ensure good insulation of the test leads. II: Select the appropriate range based on the object being tested – use the voltage range for voltage, the current range for current, and the ohm range for resistance. The test leads should be inserted into the correct sockets. When measuring voltage and resistance, insert the black test lead into the COM port and the red test lead into the V/Ω port. It is important to note that when measuring voltage, the test leads must not be inserted into the current terminals; doing so lightly may cause the meter to burn out, while doing so heavily can lead to electric shock. Therefore, before making measurements, it is essential to select the appropriate range, and the test leads must be connected correctly. When measuring DC voltage, pay attention to the polarity: the red test lead is positive, and the black test lead is negative (an analog multimeter has the opposite orientation, with the black test lead being positive and the red one negative). The NCV mode is used to detect whether wires and cables are live without making physical contact; the Live mode serves to identify the live and neutral wires in a circuit. As can be seen from the two diagrams above, the NCV mode functions like an induction test pen, allowing one to check whether a wire is connected or not, and it enables determination of whether a wire or cable has electricity present without having to cut through its insulation. And Live is the so-called Fireline L line; it’s similar to an ordinary electric tester, requiring contact with the electrical device being measured. Many multimeters these days come equipped with an NCV function as well as a temperature detection function, making them particularly suitable for air conditioner repair. Using the ammeter function of a multimeter: The ammeter function of a multimeter is not used frequently in practical applications, unless one is specifically engaged in repairing circuit boards. They connect electrical appliances in series within a circuit, as shown in the diagram. It is particularly important to distinguish between AC and DC. Voltage mismeasurement is not allowed. It can easily cause a short circuit and damage the multimeter; another thing to keep in mind is to follow the principle of working with larger values first and then smaller ones. To measure high currents, the red test lead must be inserted into the 10A socket, and care must be taken not to exceed the meter’s range. Measure the battery, with the red test lead being positive. The red color indicates the negative pole. As for the battery gauge, no further explanation is needed – it’s simply a tool used to measure the battery level. Looking at the diagram, how do we measure voltage? When we switch to the voltage setting, we first need to distinguish between the DC and AC modes. The DC voltage setting is generally used for online testing of circuit boards, and testing is always required while the circuit board is powered on. This is more commonly seen in the home appliance repair industry and in the specialized circuit board repair services provided by companies; of course, mobile phone repairs also involve online testing while the device is powered on. The AC voltage range is widely used in various applications, such as household electrical circuits, commercial buildings, and various high- and low-voltage electrical devices. The first step in repairing various electrical devices is to check whether the device is powered. It is important to note that when choosing a gauge with scales, it is essential to select the correct one; generally, for AC systems, the voltages are 20V, 200V, 600V, and 750V. Why is there 750V? Because there is also a low voltage of 660V. Online detection of AC voltage: To determine whether a circuit has leakage, a short circuit, or is open, the most important thing is to check its resistance value. So, here comes the most important setting on a multimeter: the resistance setting. The continuity of the test line is generally checked using the buzzer function. To test diodes, transistors, power tubes, etc., the diode setting can be used. To check whether a wire is conductive or not, we set the meter to the resistance setting; for example, a cable or a BV wire used in household wiring should have a resistance value of more than 500 KΩ. A value below 500KΩ but above 200KΩ indicates minor leakage, while a value below 200KΩ but above 20KΩ indicates moderate leakage. 20KΩ indicates severe leakage, and the circuit breaker will definitely trip. It is used to measure the resistance value of electrical appliances. The resistance setting can also be used to check the coils of these appliances in order to determine their condition, such as in fans, air conditioners, washing machines, rice cookers, and so on. All of these require extensive experience in maintenance. When repairing electrical equipment in a company, the ohmmeter function is often used as well; therefore, being able to use it skillfully indicates that your maintenance skills are quite good. Using a multimeter to test capacitors: Checking with the capacitor setting is quite simple – just switch it to the capacitor mode. First, discharge the capacitor, which means touching the two wires together or using a screwdriver to create a short circuit (it is essential to discharge large capacitors to prevent electric shock). If the measured capacity is lower than the specified value, it indicates that the capacitor is damaged and needs to be replaced. It’s best to keep it at the same capacity as before; otherwise, if it’s too small, it won’t be able to handle the load, and if it’s too large, the increased current can cause damage. Having written so much in general, I believe everyone now has a certain understanding of multimeters. If you are a beginner, it is recommended to purchase a relatively inexpensive multimeter and practice more. Believe that you are just one step away from being an expert. Keep going – believe in yourself!