How to test diodes

1) The forward resistance of low power germanium diode is 300ω~ 500ω, and the forward resistance of silicon working electrode tube is more than 1kω. The reverse resistance of germanium diode is a few tens of dry ohms, and the reverse resistance of silicon diode is more than 500 kω (the value is smaller for high power)

(2) According to the diode forward resistance is small, the reverse resistance is large, you can determine the polarity of the diode. The multimeter is set in the ohm gear (generally use R × 100 or R × 1k gear, don t use R × 1 gear or R × 10k gear. Because R × 1 gear with too much current, easy to burn the tube; R × 10k gear with the voltage is too high, may break through the lamp) with an iron pen were connected to the poles of the diode, measure the two resistance values in the measured resistance value of the smaller, connected to the black stylus end of the diode's positive pole. Similarly, when the measured resistance is larger, the end connected to the black stylus is the negative side of the diode. If the measured reverse resistance is very small, the diode is internally shorted; if the forward resistance is high, the pipe is internally open. In both cases, the diode needs to be scrapped.

(3) In general, the forward voltage drop of the silicon diode is zero.6V to 0.7V when the forward voltage drop of the germanium diode is 0.IV to 0.3V, so by measuring the forward conduction voltage of the diode, you can determine whether the diode is a silicon tube or germanium tube, by stringing a resistor (lkΩ) in the - end of the dry cell, and at the same time connecting the diode according to the polarity, so that the diode forward Conductivity, and then use a multimeter to measure the diode voltage drop on both sides of the tube, if 0,6V ~ 0.7V that the silicon tube turbidity 0,IV ~ 0,3V that germanium tube; if used on the road for dynamic measurements will be more convenient.