Introduction to the method of using a multimeter to detect the quality of transistors
The essence of measuring with a multimeter is to measure whether the PN junction in a transistor is normal, and the PN junction is usually located between BE and BC. Therefore, the first thing we do is to find the B pole, which is the base. In most cases, the middle one is the base. After finding the base, the next step is to use a multimeter to measure whether these two PN junctions are normal.
And the common pin of those two PN junctions is the base, so our first step is to find the base.
Find the base and distinguish the type of transistor
Firstly, use a pointer multimeter to set the ohm range X2K. Assuming that one of the poles of the transistor is the base, place the black probe on that pole and connect the red probe to the remaining two poles in sequence. If both measured results are small or large, then the assumption is correct. Otherwise, switch to another pin and continue measuring. If the selected pin is correct and both measured results are small, then the transistor being tested is NPN type, and both measured results are large, then the transistor being tested is PNP type.
Methods for detecting the quality of transistors
NPN type transistor:
Firstly, set the multimeter pointer to the X2K ohm range, connect the black probe to the base, and then connect the red probe to the other two poles in sequence. If the measurement results show that both resistance values are small, then place the red probe at the base and check the remaining two stages with the black probe. If both measurement results are large, it indicates that the transistor is normal.
The above method is not very effective for a digital multimeter. As the transistor has two PN junctions, we can choose the diode mode of the multimeter to measure the PN junction. First, place the red probe at the base and the black probe at the other two stages. If the voltage drop displayed on the screen is generally between 0.3-0.7, then the transistor is normal.
PNP type transistor:
Firstly, turn the pointer multimeter to the X2K ohm position, connect the red probe to the base, and then connect the black probe to the remaining two poles. If both measurements are small, swap the red and black probes. If both measurements are large after swapping, it indicates that the transistor is good.
For a digital multimeter, place the black probe on the base and connect the red probe to the other two ends. If the display screen can show that the voltage drop of the transistor is generally between 0.3-0.7, then the transistor is normal.
