What the displayed numbers on a multimeter stand for
Measurement of voltage
1. Measurement of DC voltage, such as batteries, portable audio power supplies, etc. First, insert the black probe into the "com" hole and the red probe into the "V Ω" hole. Select the knob to a range larger than the estimated value (note: the values on the dial are all maximum ranges, "V -" represents DC voltage range, "V~" represents AC voltage range, "A" represents current range), and then connect the probe to both ends of the power supply or battery; Maintain stable contact. The value can be directly read from the display screen. If it shows "1.", it indicates that the range is too small, and then a large range needs to be added before measurement. If a "-" appears on the left side of the value, it indicates that the polarity of the probe is opposite to the actual power polarity, and the red probe is connected to the negative terminal.
2. Measurement of AC voltage. The probe socket is the same as measuring DC voltage, but the knob should be turned to the required range at the AC gear "V~". There is no positive or negative distinction in AC voltage, and the measurement method is the same as before. Whether measuring AC or DC voltage, attention should be paid to personal safety and do not touch the metal part of the probe with your hands casually.
Measurement of current
1. Measurement of direct current. First, insert the black probe into the "COM" hole. If measuring a current greater than 200mA, insert the red probe into the "10A" socket and turn the knob to the DC "10A" position; If measuring a current less than 200mA, insert the red probe into the "200mA" socket and turn the knob to the appropriate range within 200mA DC. After adjustment, it can be measured. Connect the multimeter in series into the circuit, maintain stability, and the reading will be ready. If it displays as "1.", then the range needs to be increased; If a "-" appears on the left side of the value, it indicates that current is flowing from the black probe into the multimeter.
Measurement of AC current. The measurement method is the same as 1, but the gear should be set to AC gear. After measuring the current, the red pen should be inserted back into the "V Ω" hole. If you forget this step and directly measure the voltage, haha! Your watch or power supply will soar to the sky in a wisp of green smoke - scrapped!
Measurement of resistance
Insert the probe into the "COM" and "V Ω" holes, turn the knob to the desired range in "Ω", and connect the probe to the metal parts at both ends of the resistor. During measurement, you can touch the resistor with your hand, but do not touch both ends of the resistor at the same time, as this will affect the measurement accuracy - the human body is a conductor with a large but limited resistance. When reading, ensure good contact between the probe and the resistor; Attention to units: The unit is "Ω" in the "200" range, "K Ω" in the "2K" to "200K" range, and "M Ω" in the "2M" and above range.
Measurement of diodes
A digital multimeter can measure light-emitting diodes, rectifier diodes... When measuring, the probe position is the same as when measuring voltage. Turn the knob to the - | | -- position (this symbol will not be drawn); Connect the red probe to the positive terminal of the diode and the black probe to the negative terminal, and the forward voltage drop of the diode will be displayed. The voltage drop of Schottky diodes is about 0.2V, while 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. If the probe is swapped and the display screen shows "1.", it is normal because the reverse resistance of the diode is very high, otherwise the diode would have been broken down.
For a pointer multimeter, the red probe is connected to the negative terminal of the battery, and the black probe is connected to the positive terminal of the battery. Therefore, when using a pointer multimeter to measure a diode with a low resistance value, the black probe is connected to the positive terminal; If the resistance is high, then one end of the red probe is negative.
