How to use a multimeter to identify the transistor's tube type and pin

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Transistor tube type and pin identification is an electronic technology beginner's basic skills, in order to help readers quickly grasp the method of testing, the author summed up four formulas: "Three upside down, find the base pole; Pn Junction, fixed tube type, straight arrow, deflection large; "Let's explain it in a sentence."   One or three upside down, find the base transistor is a semiconductor device containing two PN junction. 　　According to the two PN junction connection modes, it can be divided into two types of transistors, NPN type and PNP type. Test transistor to use the Avometer ohm block, and select the Rx100 or rx1k stop. 　　The equivalent circuit of the Avometer ohm block shows that the red pen is connected to the negative of the battery in the table, and the black pen is connected to the positive of the battery in the watch. It is assumed that we do not know whether the transistor being tested is NPN or PNP, and it is not clear what each pin is. The first step in the test is to determine which pin is the base pole. At this point, we take two electrodes (such as the two electrodes are 1, 2), with Avometer two pens to measure its positive and reverse resistance, observe the deflection angle of the needle, and then take 1, 32 electrodes and 2, 32 electrodes, respectively, the reverse measurement of their positive and negative resistance, to observe the angle of the needle deflection. In these three reversal measurements, there are bound to be close to two measurement results: the reversal of the measurement of the hands of a large deflection, a small deflection; the rest of the time must be reversed before and after the measurement of the pointer deflection angle is very small, this time not measured that the foot is the base we are looking for.   PN Junction, fixed tube type after finding the base of the transistor, we can determine the type of conduction of the tube according to the direction of the PN junction between the base electrode and the other two electrodes. The multimeter of the black pen contact the base, the Red pen contact with the other two electrodes in any of the electrodes, if the table head pointer deflection angle is very large, then the test transistor is an NPN type tube; If the head pointer deflection angle is very small, then the tube is the PNP type. 　　  Three, shun arrows, large deflection to find the base B, the other two electrodes which is the collector C, which is the emitter e? Then we can use the method of measuring the penetration current ICEO to determine the collector C and emitter E. (1) for the NPN transistor, with Avometer black, red pen to measure the polarity between the positive and reverse resistance rce and Rec, although the two-time measurement of the multimeter pointer deflection angle is very small, but carefully observed, there will always be a slightly larger deflection angle, 　　At this point the current flow must be: Black →c pole →b pole →e → Red pen, the current flow is exactly the same as the direction of the arrow in the transistor symbol ("Shun arrow"), so at this time the black pen must be set electrode C, the red pen must be connected to the launch pole E. (2) for the PNP type transistor, the principle is similar to the NPN type, its current flow must be: Black →e pole →b pole →c pole → Red pen, and its current flow is also the same as the arrow in the transistor symbol, so at this time the Black table pen is connectedMust be a launch pole E, the red pen must be connected to the collector C.   Four, can not be measured, moving mouth if in the "straight Arrow, deflection large" measurement process, if the reversal of the two times before and after the measurement of the pointer deflection is too small to distinguish, it is necessary to "move the mouth." The specific method is: In the "straight Arrow, deflection large" two measurements, with two hands respectively pinch two pens and the combination of the pin, with the mouth containing (or with the tongue to resist) The base electrode B, still use "shun arrow, deflection large" method can be divided into separate collector C and emitter E. wherein the human body plays the role of DC bias resistance, the purpose is to make the effect more obvious, in order to distinguish. tags:  meter    transistor type    transistor pin    identification transistor