How to use a multimeter to test the quality of the transistors in a device
① Set the digital multimeter to the "diode test" position, insert the red probe into the (V Ω) socket, and insert the black probe into the (COM) socket. For the red probe connected to one pin, if the resistance values of the other two pins are 611 Ω or 614 Ω, it indicates that the measured transistor is an NPN type transistor. The collector of the transistor is the one with a resistance value of 611 Ω less than a few ohms, and the emitter of the transistor is the one with a resistance value of 614 Ω. On the contrary, the black probe of a digital multimeter is connected to a PNP transistor with one foot and the other two feet both at around 600 Ω. Is the foot with a lower resistance the collector of the transistor, and the foot with a higher resistance the emitter.
If three pins are measured with red and black probes, and a transistor with a resistance of 600 Ω cannot be measured, it is considered faulty. If the measured resistance value is less than 600 Ω, too much or zero, it proves that the transistor is faulty.
Sometimes, although the resistance value of a transistor can be measured at around 600 Ω, it is necessary to use a multimeter to measure the forward and reverse resistance values between the emitter and collector. In a good transistor, the resistance values of e → c and c → e are infinite, otherwise it proves that there is a problem with the transistor.
be careful; Except for diodes with damping and base and emitter with damping resistors.
② For the determined PNP or NPN transistor, the digital multimeter can be pulled to the hFE position, which is dedicated to measuring the socket of low-power transistors. Insert the three pins of the transistor in pairs, and the digital multimeter will display the amplification factor of the transistor being measured.
