First, the voltage measurement

1, DC voltage measurement, such as battery, Walkman power supply. First insert the black pen into the "com" hole and the red pen into the "VΩ". Select the knob to a range larger than the estimated value (Note: the values on the dial are the maximum range, "V-" means DC voltage, "V~" means AC voltage, "A" is current), then Connect the meter to the power supply or both ends of the battery; keep the contact stable. The value can be read directly from the display. If the display is “1.”, it means that the range is too small, then it is necessary to add a large amount of time before measuring. If "-" appears to the left of the value, it indicates that the polarity of the test leads is opposite to the actual power supply polarity. At this time, the red test lead is connected to the negative pole.

2. Measurement of AC voltage. The test lead jack is the same as the DC voltage measurement, but the knob should be turned to the range required for the AC “V~”. The AC voltage has no positive or negative points and the measurement method is the same as before. Regardless of the AC or DC voltage, pay attention to personal safety. Do not touch the metal part of the test lead with your hand.

Second, the measurement of current

1. Measurement of DC current. Insert the black test lead into the "COM" hole first. If measuring a current greater than 200mA, insert the red test lead into the “10A” jack and turn the knob to the DC “10A” position; if measuring less than 200mA, insert the red test lead into the “200mA” jack and turn the knob The appropriate range to DC within 200mA. Once adjusted, it can be measured. The multimeter is strung into the circuit and remains stable for reading. If the display is "1.", then a large amount of time is added; if a "-" appears to the left of the value, it indicates that the current flows from the black meter into the multimeter.

2. Measurement of alternating current. The measurement method is the same as 1 except that the gear position should be in the AC gear position. After the current measurement is completed, the red pen should be inserted back into the “VΩ” hole. If you forget this step and measure the voltage directly, haha! Your watch or power supply will be in the "a cloud of smoke" - scrapped!

Third, the measurement of resistance

Insert the test leads into the “COM” and “VΩ” holes, turn the knob to the desired range in “Ω”, and connect the metal parts at both ends of the resistor with the test leads. The resistance can be touched by hand during the measurement, but do not handle the same at the same time. Contact the two ends of the resistor, which will affect the accuracy of the measurement - the human body is a conductor with a large resistance but a finite size. When reading, keep the test pen and the resistor in good contact; pay attention to the unit: the unit is “Ω” in the “200” position, and the unit “KΩ” and “2M” in the “2K” to “200K” position. It is "MΩ".

Fourth, the measurement of the diode

Digital multimeter can measure LED, rectifier diode... When measuring, the position of the test leads is the same as the voltage measurement. Turn the knob to “-|>|--” (do not draw this mark); use the red test lead to connect the positive pole of the diode. The black meter is connected to the negative pole, which will show the forward voltage drop of the diode. The voltage drop of the Schottky diode is about 0.2V, the ordinary silicon rectifier tube (1N4000, 1N5400 series, etc.) is about 0.7V, and the LED is about 1.8 to 2.3V. Switching the test leads, the display shows "1." is normal, because the reverse resistance of the diode is very large, otherwise the tube has been broken.

Fifth, triode measurement

The pen is inserted as above; the principle is the same as the diode. First assume that the A foot is the base, connect the foot with the black test pen, and the red test pen and the other two feet respectively contact the other two feet; if the two readings are about 0.7V, then use the red pen to connect the A foot, the black pen If you touch the other two feet, if “1” is displayed, the A foot is the base. Otherwise, it needs to be re-measured, and this tube is a PNP tube. So how do the collectors and emitters judge? The digital table can't be judged by the pointer swing like the pointer table. What should I do? We can use the "hFE" file to judge: first hit the gear to the "hFE" file, you can see that there is a row of small jacks next to the gear, divided into PNP and NPN tube measurements. The tube type has been judged before, the base is inserted into the corresponding tube type "b" hole, and the other two legs are inserted into the "c" and "e" holes respectively. At this time, the value can be read, that is, the value of β; then the base is fixed, and the rest is fixed. The two feet are reversed; comparing the two readings, the position of the larger reading corresponds to the surface "c", "e".

Tip: The upper method can only directly measure small tubes such as the 9000 series. To measure large tubes, you can use the wiring method, that is, use three wires to lead out the three pins. This is a lot easier.

Sixth, MOS field effect tube measurement

N-channel has domestic 3D01, 4D01, Nissan's 3SK series. Determination of the G pole (gate): use the diode of the multimeter. If the positive and negative voltage drop between one foot and the other two feet is greater than 2V, “1” is displayed, and this foot is the gate G. Then exchange the test leads to measure the remaining two feet. In the case of a small voltage drop, the black meter is connected to the D pole (drain), and the red meter is connected to the S pole (source).