Summary of universal measurement function of digital multimeter
Measurement methods related to digital multimeters, including the measurement of DC voltage and AC voltage, the measurement of DC current and the measurement of AC current, the measurement of resistance by digital multimeters, the measurement of diodes, the measurement of triodes, etc.
one, voltage measurement
1. Measurement of DC voltage
Such as battery, Walkman power supply, etc. First insert the black test lead into the "com" hole, and the red test lead into the "V Ω". Select the knob to a range larger than the estimated value (note: the values on the dial are the maximum range, "V-" indicates the DC voltage range, "V～" indicates the AC voltage range, and "A" is the current range), and then turn the Connect the test lead to the power supply or both ends of the battery; keep the contact stable. The value can be read directly from the display screen, if it is displayed as "1.", it indicates that the measuring range is too small, so it is necessary to increase the measuring range before measuring. If "-" appears on the left side of the value, it means that the polarity of the test lead is opposite to that of the actual power supply. 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 measurement of DC voltage, but the knob should be turned to the required range at the AC gear "V~". There is no difference between positive and negative AC voltage, and the measurement method is the same as before. Regardless of measuring AC or DC voltage, pay attention to personal safety, and do not touch the metal part of the test lead with your hands.
two, current measurement
1. Measurement of DC current
First insert the black test lead into the "COM" hole. If measuring a current greater than 200mA, insert the red test lead into the "10A" jack and turn the knob to DC "10A"; if measuring a current less than 200mA, insert the red test lead into the "200mA" jack and turn the knob To a suitable range within DC 200mA. Once adjusted, it's time to measure. String the multimeter into the circuit, keep it stable, and you can read it. If it is displayed as "1.", then increase the range; if "-" appears on the left side of the value, it means that the current flows from the black test lead into the multimeter.
2. Measurement of AC current
The measurement method is the same as 1, but the gear should be set to the AC gear. After the current measurement is completed, the red pen should be inserted back into the "VΩ" hole. If you forget this step and directly measure the voltage, haha! Your watch or power supply will "go up into the sky in a wisp of smoke" - scrapped!
Three, resistance measurement
Insert the test leads into the "COM" and "VΩ" holes, turn the knob to the required range in "Ω", and connect the test leads to the metal parts at both ends of the resistance. During the measurement, you can touch the resistance with your hands, but do not use your hands at the same time. Contact both ends of the resistance, which will affect the measurement accuracy - the human body is a conductor with great resistance but finite size. When reading, keep the test lead and the resistor in good contact; pay attention to the unit: the unit is "Ω" in the "200" range, "KΩ" in the "2K" to "200K" range, and the unit above "2M" is "MΩ".
Four, diode measurement
The digital multimeter can measure light-emitting diodes, rectifier diodes... When measuring, the position of the test leads is the same as that of the voltage measurement, turn the knob to the " " position; connect the red test lead to the positive pole of the diode, and the black test lead to the negative pole, and the positive direction of the diode will be displayed at this time. pressure drop. The voltage drop of the Schottky diode is about 0.2V, that of ordinary silicon rectifiers (1N4000, 1N5400 series, etc.) is about 0.7V, and that of light-emitting diodes is about 1.8-2.3V. Replace the test leads, if the display shows "1.", it is normal, because the reverse resistance of the diode is very large, otherwise the tube has been broken down.
Measurement of five and triode
The insertion of the test leads is the same as above; the principle is the same as that of a diode.
Assume that pin A is the base first, connect the pin with a black pen, and touch the other two pins with the red pen; if the two readings are about 0.7V, then connect the pin with a red pen, black The pen touches the other two pins, if both display "1", then the A pin is the base, otherwise it needs to be re-measured, and this tube is a PNP tube.
