Generally, the multimeter is adjusted to that gear for diodes.
The diode symbol in the digital multimeter is the diode file. The buzzer file is used to test the open circuit. Generally, the diode file and the buzzer file are combined into one. There are also separate ones.
This gear can be used to measure the forward conduction voltage of the diode, so as to infer whether the diode is good or bad. When measuring, the red test lead must be placed on the positive pole of the diode, and the black test lead must be placed on the negative pole of the diode. The forward voltage of a good silicon diode is about 0.5-0.7 volts, and most ordinary light-emitting diodes are about 1.7 volts.
The diode file of the multimeter is for measuring diodes. Pointer multimeters generally do not have a diode file. In the era of pointer ammeters, resistance files were used to measure diodes. Then look at the scale of LV to read the forward voltage of the diode. At the same time, you can also look at the scale of LI to read the forward direction of the diode at that time. current. Silicon (silicon) diodes will be around 0.6~0.7V, germanium diodes will be around 0.2~0.3V, and Schottky diodes will be around 0.2V.
What pole is inserted into the meter to measure the resistance of the multimeter?
The head of the multimeter is a sensitive magnetoelectric DC ammeter (microammeter). When using a multimeter to measure, first adjust the gear and range, then insert the red test lead into the corresponding jack, and the black test lead into the common end jack.
When using a multimeter to measure resistance, adjust the gear to "Ω" and select the appropriate range. The meter will connect appropriate resistors in parallel and in series. At the same time, a battery will be connected in series to make the current pass through the measured resistance. According to the size of the current, The resistance value can be measured. When measuring, there is no "+" and "-" polarity for resistance. However, when measuring polar components such as crystal diodes and electrolytic capacitors, you must pay attention to the polarity of the test leads.
Use a multimeter to measure the AC voltage. Although the head of the meter is a magnetoelectric DC ammeter, when the gear is adjusted to "AC~" to measure the AC voltage, a parallel and serial half-wave rectification circuit is installed, and the AC rectification becomes After the direct current passes through the meter, the AC voltage can be measured through the magnitude of the direct current. Therefore, when measuring AC voltage, as long as the appropriate range is selected, there is no taboo for red and black test leads.
When measuring DC current and DC voltage with a pointer multimeter, pay attention to the polarity of "+" and "-". If the pointer is found to be reversed, the test leads should be replaced immediately to avoid damage to the pointer and the meter. However, when measuring DC current and DC voltage with a digital multimeter, if the polarity is reversed, there is no problem, but the display shows a negative value.
The standard method is to insert the red test lead into the hole of V/Ω, and insert the black test lead into the hole of the common terminal COM, so that both voltage and resistance can be measured.
In fact, if it is a digital multimeter, you can measure it upside down. The resistance has no polarity. If the voltage is reversed, it will display a negative value.
If it is an analog meter, the resistance can also be inserted into the test lead, but be careful when measuring the DC voltage, the test lead may burn the meter anyway.
