Clever use of the diode file of the digital multimeter
Discrimination between silicon tube and germanium tube
Use the diode gear of the digital multimeter to measure the forward voltage drop of the diode. According to the difference in the forward voltage drop of the silicon diode and the germanium diode, two different diodes can be distinguished. If the meter shows 0.500~0.700, it is detected The measuring tube is a silicon tube, if it shows 0.150~0.300, the tested tube is a germanium tube.
Discrimination of the polarity of the diode
Put the digital multimeter in the diode position. At this time, the red test lead is positively charged, and the black test lead is negatively charged. The two test leads are respectively connected to the two pins of the diode. If the displayed value is below 1v, it means that the tube is in a forward conduction state, and the red test lead is connected to the diode. It is the positive pole, and the black test lead is connected to the negative pole. If the displayed value is "1", it means that the tube is in a reverse non-stop state. The black test lead is connected to the positive pole, and the red test lead is connected to the negative pole. For light-emitting diodes, the diode glows when it is measured in the forward direction, and the tube voltage drop is about 1.7v.
Discrimination of good and bad diodes
Put the digital multimeter in the diode position. At this time, the red test lead is positively charged, and the black test lead is negatively charged. The two test leads are respectively connected to the two pins of the diode. If the two display values are "000", it means that the tube has been broken down. If If the two display values are "1", it means that the inside of the tube has been disconnected.
Discrimination of base and tube type of triode
The triode is formed by a PN junction at the boundary between two different dopant accumulation regions. The inside is like a combination of two diodes, the middle one is the base (B pole), the base of the PNP tube is the common point of the two negative poles, and the base of the NPN tube is the common point of the two positive poles. In the actual measurement, first find the base and judge whether it is a PNP or NPN tube. Set the multimeter switch to the diode position, because the diode position of the digital multimeter has a voltage output of about 2.7v, use the unidirectional conductivity of the PN junction to judge the base and judge the NPN and PNP type transistors
