Multimeter to determine the polarity of the diode ohms file
In general, the diode coloured point of the end is positive, such as 2AP1 ~ 2AP7, 2AP11 ~ 2AP17, etc.. If the diode is a transparent glass case diode, the polarity can be seen directly, that is, the internal end connected to the contact wire is positive, and the end connected to the semiconductor sheet is negative. Plastic-coated diodes with a circle mark is negative, such as the IN4000 series.
No marking of the diode, the multimeter resistor to identify the positive and negative poles, the multimeter resistor block schematic diagram in Figure T304.
According to the characteristics of the diode forward resistance is small, reverse resistance is large, the multimeter will be dialled to the resistance block (generally use R × 100 or R × 1k block. Do not use R × 1 or R × 10k block, because R × 1 block using too much current, easy to burn the tube, and R × 10k block using too high a voltage, may break through the tube). With the meter pen connected to each pole of the diode, measure the two resistance values. At the smaller measured resistance, the end connected to the black pen is the positive terminal of the diode. Similarly, in the measured larger resistance value of a time, and the black pen connected to the end of the diode's negative terminal. If the measured positive and reverse resistance are very small, indicating that the tube is short-circuited; if the positive and reverse resistance are very large, then the tube is open-circuited. In both cases, the tube can not be used. (Inside the multimeter, the black pen is connected to the positive terminal of the internal battery.)
For light-emitting diodes, in general, the electrode is smaller, shorter one is the positive pole of the light-emitting diode, the electrode is a larger one is its negative pole. If you buy a new foot longer one is the positive pole.
