An easy way to measure the three pins of a triode with a multimeter
Triode is composed of a core (two PN junctions), three electrodes and a tube shell, the three electrodes are called collector c, emitter e and base b. Currently, the common triode is a silicon planar tube, which is further divided into two categories: PNP and NPN type. Now germanium alloy tube has been rare. Here electrician home to introduce how to use the multimeter to measure the three pins of the triode simple method.
1. Find out the base pole, and determine the tube type (NPN or PNP)
For PNP-type transistor, C, E pole for its internal two PN junction positive pole, B pole for their common negative pole, and for NPN-type transistor, it is just the opposite: C, E pole for the negative pole of the two PN junction, while the B pole for their common positive pole, according to the PN junction positive resistance of the resistance of small reverse resistance of the characteristics of the large can be very easy to determine the base and the type of the tube. The specific method is as follows:
The multimeter will be dialed on the R × 100 or R × 1K gear. Red pen contact a pin, with the black pen were connected to the other two pins, so that you can get three groups (each group of two) readings, when one of the second measurement is a few hundred ohms of low resistance, if the public pin is the red pen, the contact is the base, and transistor tube type for the PNP type; if the public pin is the black pen, is also the base of the contact and transistor tube type for the NPN type.
2. Identify the emitter and collector
As the triode in the production, two P area or two N area of the doping concentration is different, if the emitter, collector use the correct, triode has a strong amplification, on the contrary, if the emitter, collector interchangeable use, the amplification is very weak, which can be the tube emitter, collector to distinguish between.
After identifying the tube type and base b, the following methods can be used to identify the collector and emitter.
Set the multimeter to R×1K. Hand pinch the base and another pin together (pay attention not to let the electrodes directly touch), in order to make the measurement phenomenon is obvious, you can wet your fingers, will be connected to the red pen with the base pinch together on the pin, the black pen connected to the other pin, pay attention to observe the magnitude of the multimeter pointer swing to the right. Then the two pins to the right, repeat the above measurement steps. Compare the amplitude of the needle swinging to the right in the two measurements, and find out the amplitude of the large swing. For PNP-type transistors, the black pen is connected to the pin with the base pinch together, repeat the above experiments, to find the needle swing amplitude, for NPN-type, the black pen is connected to the collector, the red pen is connected to the emitter. For PNP type, the red pen is connected to the collector, the black pen is connected to the emitter.
The principle of this method of discriminating electrodes is to use the internal battery of the multimeter to add voltage to the collector and emitter of the transistor, so that it has the ability to amplify. Hand pinch its base, collector, it is the same as through the hand of the resistance to the triode plus a positive bias current, so that it conducts, the needle swings to the right at this time to reflect the magnitude of its amplification ability, and therefore can be correctly identified emitter, collector to.
