Multimeter is a must-have test tool in electronic production. It has a variety of functions such as measuring current, voltage, and resistors. This section will introduce the structure of the multimeter and the method of using the multimeter. The students should study hard to use the multimeter. First, observe and understand the structure of the multimeter. There are many types of multimeters, which are different, but the basic structure and methods of use are the same. The structure and shape of the commonly used meter are shown in the drawings. The king must have a head and selection switch on the multi-purpose surface panel. There is also an ohmic gear zero knob and a table pen jack. The role of each part is described below: (1) The head of the meter of the meter is a sensitive current meter. The dial is printed on the header with multiple symbols, ticks and values (as shown in Figure 3-4 (b)). Symbol A One V-Ω means that this meter is a multimeter that can measure current, voltage, and resistance. A plurality of ticks are printed on the dial, where the right end is marked with "Ω" is a resistance line, the right end is zero, the left end is ∞, the scale value distribution is uneven. Symbol "-" or "DC" represents DC, "~" or "AC" represents AC, "~" represents a scale line for AC and DC shared. The number of numbers under the scale line is the scale value corresponding to the different gear positions of the selection switch. There is also a mechanical zero-adjustment knob on the header to correct the pointer to zero at the left end. (2) Select the selection switch of the switching meter is a plurality of gear rotation switches. Used to select measurement items and ranges. (Figure 3 4 (b)). The general multimeter measuring items include: "mA"; DC current, "V": DC voltage, "V": AC voltage, "Ω": resistance. Each measurement project is divided into several different ranges for selection. (3) The form pen and the table pencil form pen are divided into red and black. The red table should be inserted into the jack labeled " ", and the black table pen is inserted into the jack labeled "-". Second, the use of multimeter (1) Before using the multimeter, you should do: 1. Multimeter level is placed. 2. Check if the gauge stops parked on the left end of the dial. If there is a deviation, you can gently turn the mechanical zero adjustment knob on the head with a small screwdriver to make the table needle finger zero. 3. Put the table on the table inserted the table. 4. The selection is selected to rotate to the corresponding item and range. You can use it. (2) After using the multimeter, you should do: 1. Pull out the pen. 2. The selection is selected to rotate to the "OFF" file. If there is no file, it should be rotated to the maximum amount of the AC voltage, such as "again 1000V" file. 3. If it is not used for a long time, the end battery should be taken out to prevent the internal circuitry to prevent the battery electrolyte leakage and corrode the internal circuit. Multimeter Measurement Voltage and Current in electronics, often measure the voltage and current in the circuit with a multimeter. The light-emitting diode and resistor, the potentiometer into the circuit of Figures 3-4, and the rotary potentiometer makes the light emitting diode light emission. LED is a special diode. When a certain current, its transparent housing will be emitted. The light emitting diode has a variety of colors, often doing an indicator in the circuit. We will use this circuit to exercise the voltage and current using the multimeter. (1) Measuring the DC voltage as an example of JO411 million menu. The measurement step is: 1. Select the range. The multimeter DC voltage file is marked with "V", 2.5 volts, 10 volts, 50 volts, 250 volts and 500 volts. Select the range according to the power supply voltage size in the circuit. Since the power supply voltage in the circuit is only 3 volts, 10 volts are selected. If the voltage is not clear, the highest voltage file should be measured first, and the low voltage file is gradually exchanged. 2. Measurement methods. The multimeter should be parallel to the measured circuit.
The red pen should be subjected to the circuit and the power supply positive electrode, and the black pen should be subjected to the circuit and the power supply negative electrode (as shown in Figures 3-4). Figure 3 4 Using a mesh measurement voltage 3. Correct reading. Carefully view the watch plate, the DC voltage file scale is the second scale. When using a 10V file, the third row of the third row of the third row of the measured voltage is read out directly from the third row of numbers. Pay attention to the reading, the sight should be positive to the pointer. Skill Training Use the multimeter to measure the voltage purpose practice connection circuit and measure the voltage using the multimeter. Equipment Battery 2 (placed in battery case) 100FLL / 8W fixed resistance, 470T1 potentiometer, light emitting diode, wire, and multimeter. Step (1) Connect the circuit as shown in Figure 3-4. The circuit does not do welding. The wires can be insulated from both ends of the wire to the component contact or leads. Note that adjacent contact between the leads cannot touch. Circuit connection method (2) Check the circuit error after the circuit is turned on, and the brightness of the rotating potentiometer will change. Mix the light emitting diode brightness. (3) Prepare the multimeter to be prepared before the previous use, and place the selection switch to the VL0 volt. (4) Handheld pen insulated rods, contacting the pens and negative poles of the battery pack, the positive and negative poles, and the power supply voltage is measured. Read the voltage value correctly. Record: The power supply voltage is up. (5) Turn the multimeter red black list pen into contact with the light-emitting diode two-pin pin, and measure the voltage of the light-emitting diode. Read the voltage value correctly. Record: The voltage between the light-emitting diode is a vol. (6) Measure the voltage of the fixed resistor by the multimeter. First, it is determined that the positive and negative form should be in contact, and then measure it. Record: The voltage at both ends of the fixed resistor is a volt. In the measurement of the above three steps, if the voltage value is less than 2.5 volts, the multimeter can be selected to change to a V2.5 volt file, compare the measurement results (the transfer of the tick reading after the change process) . (7) After the measurement is complete, the circuit power is turned off. Required by the requirements after the use of the multimeters mentioned earlier. (2) Measure DC current 1. Select Range: Wanli Table DC current file marked with "MA" with 1mA, 1Oma, 100mA three-speed range. Select the range and should be based on the current in the circuit. If you don't know the current size, you should use the maximum range. 2. Measurement Method: The multimeter should be connected in series with the measured circuit. When the circuit should be disconnected, the multimeter should be used on both ends of the breakpoint. The red table pen should be attached to the breakpoint connected to the positive electrode, the black table pen is connected to the breakpoint connected to the power supply negative (as shown in Figure 3-6). Figure 3-6 Measuring the current 3 with a multimeter. Correct reading: DC current stall tick is still a second, if you choose 100mA file, you can use the third row of numbers, and take 10 after reading. Skill training uses a multimeter measuring current. Purpose Exercise Use the multimeter to measure DC current. The equipment still uses the circuit of Figure 3-4 (measurement voltage), a multimeter. Step (1) Connect the circuit as shown in Figure 3-4, so that the light emitting diode is normally illuminated. (2) Prepare the multimeter as required before the previous use, and place the selection switch in the MA file 100 mA range. (3) As shown in Figure 3-6, the intermediate connection point and the light-emitting diode negative electrode between the discharge potentiometer are turned off, and "breakpoint" is formed. At this time, the light emitting diode is extinguished. (4) Since the multimeter is connected in series at the breakpoint. Red Table Brown Brigadier Diode Negative Negative Negotic Negative Negative Node, Black Table Pen Potentiometer Intermediate contact lead. At this time, the light emitting diode re-lifted.
The metric value of the mean table pointer is the current value through the light emitting diode. (5) The current value of the light emitting diode is correctly read. Record: The current through the light emitting diode is mA. (6) Rotate potentiometer handle, observe the change of the multimeter pointer and changes in the brightness of the light emitting diode, it can be seen:. Record: The maximum current through the light emitting diode is mA. The minimum current is mAh. Through the above operation, we can further understand the role of the resistor in the circuit. (7) After the measurement is complete, disconnect the power, and collect the multimeter as required. Fourth, use a multimeter and electrical and test electronic components (1) Measuring the resistance of the resistance using the multimeter measuring meter can measure the resistance of the conductor. The ohmic file is represented by "Ω", divided into R × 1, R × 10, R × 100 and R × 1K four files. There are also R × 10k files in some million wheels. Using a multimeter ohm gear measurement resistance, the following steps should be followed in addition to the requirements before using the previous use (see Figure 3-7). 1. Place the selection switch in the R × 100 file, short the two tablets to adjust the ohm gear zero adjustment knob, and make the tablets to the zero position at the right end of the resistance. If the pointer cannot be adjusted to zero, the battery voltage is insufficient, and the battery should be replaced (as shown in Figure 3-7 (a)). 2. The two sheets are used to be measured separately by the two-pole. Correctly read the value of the resistance referred to in the pointer, multiplied by the magnification (R × 100), and the R × 1k file should take 1000 ...). It is the resistance of the measured resistance (as shown in Figure 3-7 (b)). 3. In order to make the measurement more accurate, the pointer should refer to the center position of the scale line. If the pointer is small, the R × 1k file should be exchanged. If the pointer is large, the R × 1O gear or R × 1 gear should be changed. After each shift, the ohm gear zero adjustment knob should be adjusted again, then measure (as shown in Figure 3-7 (c)). 4. After the measurement is over, the table should be pulled out to place the selection switch in the "OFF" file or the maximum AC voltage maximum gear. Collect the multimeter. Note when measuring the resistor: 1. The measured electricity should be removed from the circuit and then measured. 2. Two cars should not touch it for a long time. 3. Two hands cannot touch the metal rods of the two cautions, or two pins that are measured by the electric resistance, preferably with the right hand to hold two sheets (as shown in Figure 3-8). 4. It is not used for a long time to take out the battery in the table. Skill Training Using Multimeter Measuring Resistance Purpose Effects of Eym Genergic Methods for Emini Multi-Mechanism, Exercise Using Multimeter Measuring Resistance. Table 3-7 Wen Table Test Common Electronic Components
Test the capacitor with a wide range of capacitors (5000p) with a larger capacitor (5000P), and the multimeter pointer will gradually return to the left, and the power resistance value refers to this capacitive insulation resistance when the pointer is stopped. The bigger the insulation resistance, the better, generally should be close to ∞ If the pointer does not move, the capacitor has been disconnected, the swing is not returned, and the capacitor is seriously leaked, and it cannot be used. Smaller capacity (5000P or less) When the curved needle is basically non-motion electrolytic capacitor, the red pen is applied to the electrolytic capacitor, the black pen is connected to the power, the larger the capacitance, the larger the gauge swings, and after each measurement The capacitors should be short-lived on both ends of the capacitor. Test crystal diode measuring diode forward resistance resistance value is, better. Measure the diode reverse resistance. The bigger the resistance is, the better. Test crystal triode test triode penetrate current. The NPN tube is shown in the picture (PNP type blade) CE pole resistance, the larger the resistance value, the smaller the three-pole penetration current, the better the working stability, when the hand holds this tube, the resistance value gradually decreases, The triode is very stable. The triode amplification capacity adds a 100K resistor between the three poles of the triode CB in the precedent measurement, and the gauge should be swinging to the right swinging angle, the larger the triode is magnified. (If there is no resistance, it is also possible to pinch the BC pole with the left hand to instead of the body resistance instead of the equipment multimeter. Different resistance (1) Put 10 resistance on the cardboard. According to the colored ring on the resistance, write Their nominal value. (2) Adjust the multimeter as required, and placed in the R × 100 file, adjust the ohmic gear zero adjustment knob to transfer zero. (3) Measure 10 resistance. Write the measured value to the resistance Pay attention to the readation ratio of reading at the time of measurement. (4) If the pointer is too large when the measurement is measured, it should be measured after shifting. After the shift should be zeroed again. (5) inspection. 10 resistance How many of your measurement is correct? Compare the measurements and nominal values. (6) Collect the multimeter as required. (2) Test electronic components with multimeter Euphore can also test capacitors, diodes And the triode, test method can be referred to in Table 3-7. Other electronic components are applied in later applications, and then describe test methods. Skill training utility table test electronic component purpose practice using multimeter test capacitor, crystal diode and triode. Equipment multimeter fixed capacitor 1000P 0.1 1 μ 1μ, 10 μ 100μ, electrolytic capacitor, diode 2AP9, 2CP10 triode 3DG6 3A × 31 Step (1) Adjust the multimeter, placed in R × 1k file. Adjust the ohm gear zero adjustment knob for zeroing. (2) Measure the insulation resistance of 1000P 0.1 μ, 1μ, 1μ, and observe the swing of the mean table pointer, recorded in Table 3-8. (Practice the right hand in the right hand when measured) (3) Measurement 10 μ, 100μ electrolytic capacitor insulation resistance and observe the swing of the table needle (pay attention to the correct connection of the positive and negative sheet). The capacitor should be discharged after each test. Record in Figure 3-8. Table 3-8 Test Capacitor Record
Insulation resistance surface needle swings 1000P 0.1μ 1μ 10μ 100μ
According to the record of the above table, think about it, what kind of capacitor is better? (4) Measure the positive and reverse resistance of the diode, recorded in Table 3-9. Table 3-9 Test Diode Record
Positive resistance reverse resistor 2ap9 2cp10
According to the record of the above table, think about it, what kind of crystal diode quality is better? (5) Test crystal triode 1 measured between the CE poles. Pay attention to the table pen. (NPN-type triode: black pen pick C, red pen pick E.PNP tri-three) This value should be larger (greater than a few hundred thousand Euro). At the same time, hold the housing by hand, so that it is warmed, at this time, the resistance value is small, the greater the change, the worse the triode stability. 2 On the previous step, the 100K resistance is applied between the BC poles (also pinched with the BC of the BC), and observe the right span of the tablet, the larger the swing of the needle, the greater the magnitude of the triode. Record the test case in Table 3-10. Table 3-10 Test triode recording type tube type CE resistance stability BC indirect resistance meter Needle swings enlargement capacity 3DG6NPN 3A × 31PNP
I want to think about: According to the above, do you preliminate the method of testing common electronic components with a multimeter? Thinking and practicing 1. The multimeter is mainly used for measurement. What is the steps of the use of a multimeter? What should I pay attention to in use? 2. I want to think about how to test the potentiometer with a multimeter, do it, see what potentiometer is good. 3. Some multimeters, such as the MF-50 have direct measurement of the genre between the multiplicity amplifier, and the corresponding triode jack, please demonstrate the method of measuring the multiplicity amplification multiple using this multi-purpose table. Actually measure a few triodes test.
