Knowledge of multimeter, how to use it?
How to use the multimeter? This is a small problem for many novice electricians or friends at home. They don’t know how to use the multimeter. Today, let’s talk about the function of the multimeter. The multimeter is an indispensable measuring instrument for electricians. Generally, it is used to measure voltage, Current and resistance are the main purposes. Multimeters are divided into pointer multimeters and digital multimeters according to the display method. It is a multi-functional, multi-range measuring instrument, also known as a three-purpose meter or a multi-purpose meter. Because digital multimeters are more precise, more intuitive, and simpler, we focus on digital multimeters. However, the advantages of pointer multimeters in circuit board maintenance are indeed better than digital multimeters, and each has its own strengths.
One: Before measuring, make sure that the multimeter is in good condition and the reading is correct. Pens are in good condition. Attachments are in good condition. Especially when measuring high voltage, it is necessary to ensure that the test leads are well insulated.
Two: Select the appropriate gear according to the measured object, choose the voltage gear for the voltage, choose the current gear for the current, and choose the ohm gear for the resistance. The test leads should be inserted in the correct jacks. When measuring voltage and resistance, insert the black test lead into the COM port and the red test lead into the V/Ω port. Special attention, when measuring the voltage, the test leads cannot be inserted into the current interface. If it is light, the meter will be burned, and if it is serious, an electric shock accident will occur. Therefore, you must choose the appropriate gear before measuring, and the test leads must be connected correctly. When measuring DC voltage, pay attention to the polarity, the red test lead is positive, the black test lead is negative (the pointer multimeter is opposite, the black test lead is positive, and the red test lead is negative).
The ncv file is equivalent to an induction pen, which can check the continuity of the wire, and you can know whether the wire and cable are powered without breaking the skin. And live is the legendary FireWire L line, which is equivalent to an ordinary electric pen and needs to be contacted with electrical equipment for measurement. Nowadays, many multimeters have NCV function and the function of detecting temperature, which is especially suitable for air conditioner maintenance.
The meter current file is not often used in practical applications, unless it is specialized in repairing circuit boards. They connect electrical appliances in series in the circuit, as shown in the figure. Special attention is that AC and DC must be distinguished. Do not mismeasure the voltage. It is easy to cause a short circuit and cause damage to the multimeter. Another thing to note is that the principle of first big and then small should be followed. To measure a large current, you need to insert the red test lead into the 10A socket, and be careful not to exceed the range of the meter.
As for the battery file, there is no introduction, it is very simple and intuitive to measure the battery. Let's look at the picture, how to measure the voltage? When we switch to the voltage file, we must first distinguish the DC file from the AC file. The DC voltage DC file is generally used in the on-line detection of the circuit board, which requires live detection. This is more common in the home appliance repair industry and the company's professional circuit board repairs. Of course, mobile phone repairs are also online live detection. AC voltage file AC file, this application is more extensive, home circuit company shopping malls, various high and low voltage equipment electrical. The first point of repairing various electrical equipment is to measure whether the electrical appliances have electricity. It should be noted that the meter with scale must be selected correctly. Generally, the AC has 20v200v600v750 volts. Why is there 750v? Because there is still low voltage 660V.
To judge whether a line is leaking and short-circuited, the most important thing is to check its resistance. Then the most important gear of the multimeter comes, the resistance gear. The on-off of the detection line generally uses the buzzer file. To detect diodes, triodes, power tubes, etc., you can use the diode file.
We hit the resistance file, such as a cable or a bv line for household electricity, the resistance value should be greater than 500KΩ. If it is lower than 500KΩ and greater than 200KΩ, it means a slight leakage, and if it is lower than 200KΩ and higher than 20KΩ, it means a moderate leakage. 20KΩ represents severe leakage, and the leakage protector must trip.
Electrical barriers can also detect the coils of electrical appliances to confirm whether they are good or bad, such as electric fans, air conditioners, washing machines, rice cookers and so on. These all require long-term maintenance experience. The maintenance of electrical equipment in the company often requires the use of resistance gears, so being able to use resistance gears proficiently means that your maintenance skills are very good.
Capacitance file inspection is relatively simple, directly dial to the capacitor file. Discharge the capacitor first, that is, touch the two wires together, or short-circuit them with a screwdriver (large capacitors must be discharged to prevent electric shock). If the measured capacity is lower than the marked capacitance, it means that the capacitor is damaged and needs to be replaced. It is best to have the same capacity as the original, otherwise the load is too small and cannot be carried, and the load current is too large and it is easy to burn.
