Mnemonic for measuring the transistor base with a multimeter
Triode type judgment and pin discrimination belongs to the electronic foundation, general electrotechnical beginners will be exposed to three upside down, find the base pole; PN junction, set the tube type; Shun arrow, deflection large; measurement is not allowed to move the mouth. Perhaps it is much easier, of course, the mnemonic memorized but do not know the meaning, that is also useless.
Multimeter measurement triode base method
The first sentence of the mnemonic: three upside down, find the base pole
As you know, the triode is a semiconductor device containing two PN junctions (not two separate PN junctions in series).
(not two separate PN junctions in series). According to the two PN junctions connected in different ways, the triode can be divided into NPN type and PNP type.
Triodes are tested using a multimeter with an ohm stop of R×100 or R×1k. As for the pointer type multimeter, the red pen is the negative pole of the multimeter and the black pen is the positive pole of the multimeter battery. When testing the triode tube type, the first step is to determine the base position of the pin. Measurement method: randomly select two electrodes (such as these two electrodes for 1, 2), first measure the positive and negative resistance, observe the deflection angle of the meter needle; then, then take 1, 3 two electrodes and
2, 3 two electrodes, respectively, inverted to measure their positive and negative resistance, observe the deflection angle of the needle. In these three inverted measurements, there must be two measurements are similar: that is, inverted measurements in the needle deflection, a deflection of a large, a deflection of a small; the remaining one must be inverted before and after the measurement of the pointer deflection angle is very small, which is not measured that the pin is the base we are looking for!
NPN triode (left) and PNP triode (right) circuit symbols
Mnemonic second sentence: PN junction, find the tube type
After the appeal measurement, we determine the base of the pin, we can determine the tube type according to the base and the other two electrodes between the PN junction direction. Measurement method: the black pen of the multimeter is placed at the base, the red pen is placed on any of the remaining electrodes, if the head pointer deflection angle is very large, then the measured transistor for the NPN-type tube; if the head pointer deflection angle is very small, then the measured tube that is the PNP type.
NPN type triode structure and current flow direction
NPN-type triode: according to the principle of NPN-type triode penetration current flow, with a multimeter black, red pen upside down measurement between the two poles of the positive and negative resistance Rce and Rec, to get the results of the two measurements, found that the pointer deflection head are small, after careful observation, will find that there is a deflection angle deflection of a little bit, that is, the current flow: black pen → c pole → b pole → e pole → red pen, the flow coincides with the direction! Triode symbols of the flow direction of the arrow, so this time the black pen must be connected to the collector c, the red pen must be connected to the emitter e.
