How to use a multimeter to evaluate the quality of a transistor
First, use the "diode and buzzer on-off" gear of the digital multimeter to judge whether the transistor is good or bad and whether the transistor is PNP or NPN.
①Turn the digital multimeter to the "diode test" position, insert the red test lead into the (ⅤΩ) jack, and the black test lead into the (COM) jack. For the red test lead connected to one pin, the resistance value of the other two pins is 611Ω or 614Ω, which means that the triode measured at this time is an NPN type tube, and the resistance value of 611Ω is a few ohms less than the collector of the triode, and the resistance value of 614Ω is the collector of the triode. launch set. On the contrary, the black test lead of the digital multimeter is connected to one pin and the other two pins are about 600Ω. The triode is a PNP type triode, and the pin with a small resistance is the collector of the triode, and the one with a larger resistance is the emitter.
If the three pins are measured with red and black test leads, no 600Ω resistance triode can be detected, it is bad. If the measured resistance value is too much less than 600Ω or is zero, it proves that the triode is bad.
Sometimes, although the resistance value of about 600Ω of the triode can be measured, at this time, a multimeter must be used to measure the forward and reverse resistance values between the emitter and the collector. For a good triode, e→c, c→e The resistance value is ∞ infinite, otherwise it proves that there is something wrong with this triode.
Note; except for damped diodes and base and emitter damped resistors.
②For the determined PNP or NPN triode, you can pull the digital multimeter to the hFE position at this time, which is a jack dedicated to measuring low-power triodes. Insert the three pins of the triode with the corresponding marks, and the digital multimeter will display the magnification of the triode under test.
