Method for judging transistor pins by multimeter
Firstly, pull the three pins of the transistor back and forth or left and right a certain distance to facilitate measurement; This can avoid short circuits in the probes,
2. Set the ohm range of the pointer multimeter to the R × 1k range, and measure the resistance between any two pins in the forward and reverse directions once. The smaller resistance value should be taken as the standard. The black probe should be connected to the p area, and the red probe should be connected to the n area. Mark it and continue to measure the next group, also marking it. If there is a common p or n area measured four times (twice for any two pins), it can be determined that it is an npn or pnp type transistor. That is, if there is a same p area, it is npn type, and if there is a same n area, it is pnp type. That's the base. Another situation is that the positive and negative resistance between two pins is similar, so these two pins are the emitter and collector regions; In general, the above measurements need to be conducted six times (with three legs and two legs measured in both directions once, depending on the arrangement and combination, six measurements can be taken), which can also be used to determine the quality of the transistor. But sometimes measuring any two pins separately twice, and exactly measuring the small resistance value, in this case, the polarity can be determined by two measurements.
After determining the polarity of the tube, the base is also determined, and the next task is to determine the emitter and collector;
For example, the tested transistor is an NPN transistor
1. Pinch the base and one of the pins (assuming the pin is the collector) with your thumb and index finger. Note that the base and the electrode cannot be in direct contact, but are connected through your finger. At this point, your finger is equivalent to a larger bias resistor. Connect the black probe to the assumed collector (assuming the collector and base are connected in parallel, both positive), and connect the red probe to the assumed emitter. Record the displayed value R1;
2. Then pinch the base and the other foot (assuming that the foot is the collector) with your thumb and index finger
3. Compare the results of two measurements. If R1 is greater than R2, then the assumed result of the second measurement is correct. Conversely, if R1 is greater than R2, then the first measurement is correct;
The method for measuring PNP transistors is the same as above, except that the base should be connected to the negative electrode (red pen).
