How to use a multimeter to test the quality of transistors
Firstly, use the "diode and beep on/off" gear of a digital multimeter to determine the quality of the transistor and whether it is PNP or NPN type.
① Set the digital multimeter to the "Diode Test" position, insert the red probe into the (V Ω) socket, and 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 resistor value of 611 Ω is a few ohms lower than the collector of the transistor, and the resistor value of 614 Ω is the emitter of the transistor. On the contrary, the black probe of a digital multimeter connected to one of the other two pins of a transistor with a resistance of around 600 Ω is a PNP type transistor, or is the lower resistance pin the collector of the transistor and the higher resistance pin the emitter.
If three pins are measured with red and black probes, a transistor with a resistance of 600 Ω cannot be measured, and it is considered faulty. If the measured resistance value is less than 600 Ω, which is too much or zero, it proves that this 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. For a intact transistor, the resistance values of e → c and c → e are infinity, otherwise it proves that there is a problem with the transistor.
Attention; 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 a dedicated socket for measuring low-power transistors. Insert the three pins of the transistor with corresponding numbers, and the digital multimeter will display the amplification factor of the tested transistor.
