Use of digital multimeter
(1) Measurement of DC voltage
First insert the black test lead into the COM jack, and the red test lead into the v/Ω jack. Then, set the function switch to the DCV range, select an appropriate range according to the measured DC voltage, turn the function switch to the corresponding position, and connect the test pen in parallel to the power supply or load to be tested. If you do not know the measured voltage range, you should set the function switch to the maximum range. If the display only shows 1, it means that the measured voltage has exceeded the range , and the function switch should be adjusted up.
(2) Measurement of AC voltage
Except that the function switch is adjusted to the ACV range, other operations are the same as DC voltage measurement.
(3) DC current measurement
Insert the black test lead into the COM hole, and when measuring the maximum current within 200mA, insert the red test lead into the mA jack. According to the size of the measured DC current, select the appropriate range, and turn the function switch to the corresponding gear of DCA. When the measured current is above 200mA but less than 20A, insert the red test lead into the 20A jack, and connect the test lead to the circuit to be tested. If the measured current range is not known before use, the function switch should be placed the maximum range. If the display only shows 1, it means that the test current has exceeded the selected range, and the function switch should be set to a higher gear.
(4) AC current measurement
Except setting the function switch to the ACA range, the others are the same as DC current measurement.
(5) Measurement of resistance
Insert the black test lead into the COM jack, and the red test lead into the v/Ω jack. Set the function switch to the appropriate gear of the Ω range, and the two test leads are connected to the resistance or the two ends of the circuit. If the measured resistance value exceeds the maximum value of the selected gear, 1 will be displayed, and the range gear should be increased at this time. If the maximum range is selected and 1 is still displayed, the measured object may be disconnected.
(6) Capacitance measurement
The digital meter has a special capacitance test socket. When measuring , depending on the capacity of the capacitor, turn the function switch to an appropriate position in the C range . Just insert the two pins of the measuring capacitor directly . If the capacitance value exceeds the selected range, 1 will be displayed, and the range must be increased . If the capacitance value and gear selection are appropriate and 1 is still displayed, the capacitor may be short-circuited.
(7) Diode and short circuit test
Insert the black test lead into the COM jack, the red test lead into the V/Ω jack, and set the function switch to the position marked with the diode icon. Connect the black test lead to the negative pole of the diode, and the red test lead to the positive pole of the diode, and the reading is the forward voltage drop value of the diode. The two test leads are connected to two points of the line . If the resistance value is lower than 70Ω, the built-in buzzer will sound, indicating that the two points are short-circuited.
(8) Triode test
Set the function switch to the hef range, and according to whether the transistor is NPN or PNP, insert the collector, base, and emitter into the dedicated corresponding jacks on the panel, and you can read directly.
Some Explanations in Digital Multimeter Test
(1) For the high-resistance range, it is normal that the resistance test results are different from the pointer meter test results, which is mainly due to the slightly different test conditions.
(2) When testing the physical quantities related to the polarity, the polarity displayed on the test leads is corresponding. That is to say, when the polarity is not displayed , when the contact of the red test pen is the high end of the potential or "-", the contact of the red test pen is the low end of the potential or the current output terminal.
(3) The resistance file and the diode file are different from the pointer meter. When the pointer meter measures the resistance, the polarity of the red and black test leads is opposite to that is, the black test lead is the positive terminal of the test source, but it is consistent with the polarity of the test source, that is The red test lead is the positive terminal of the test source, and the black test lead is the negative terminal, which is consistent with the voltage, current, etc., so that there will be no confusion, and it is superior to the pointer meter.
(4) For the triode whose polarity or pin arrangement sequence is not known , the electrodes of the triode can be identified and determined by changing the pins of the triode hfe gear multiple times .
(5) Calibration. The digital multimeter should be calibrated regularly. When calibrating, the digital instrument of the same type or with higher precision should be selected. First, the DC gear, then the AC gear, and finally the capacitance gear.
Precautions for using digital multimeter
(1) The measurement of each function of the digital meter is powered by the internal battery . In order to save battery, please turn off . When the power switch is turned on, if the battery symbol flashes on the display, it means that the internal battery voltage is low , and a new battery should be replaced.
(2) During the test, the function switch shall not be switched. If it is necessary to change the gear or change the range, it must be done after the test leads are separated from the circuit.
(3) The equivalent resistance of the human body cannot be measured with a digital meter, because there is a distributed capacitance between the human body and the earth, and a strong 50Hz AC voltage signal can be induced on the human body, thereby causing the range to exceed the limit.
(4) Before measuring the capacitance, it is necessary to ensure that the capacitor does not store electric energy, otherwise it should be discharged. Otherwise, the circuit inside the meter will be damaged.
(5) When the fuse in the meter is blown, it must be replaced , and the specification must not be changed at will.
(6) Do not use or store in direct sunlight or high temperature environment , otherwise the LCD screen of the digital meter will be easily damaged.
(7) When the digital meter is not used for a long time, the battery in the machine should be taken out and stored properly.
(8) Once there is a problem with the digital meter, it is strictly forbidden to mess with the components , and must be repaired by a professional.
