Multimeter How to measure transistor _ multimeter test transistor good or bad diagram

First, the multimeter to the test diode end, with the multimeter of the Red pen to one of the transistor's pin, and the other side of the multimeter to test the remaining pins, until the following results are tested:

1, if the transistor's black form pen to connect one of the pins, and the Red Watch pen to test the other two pins are on the voltage display, then this transistor is PNP transistor, and the black pen is connected to the foot of the transistor base B, the above method when the red pen of the multimeter is connected to one of the foot voltage is slightly higher, Then the PIN is the emitter e of the transistor, and the remaining low voltage pin is the collector C.

2, if the transistor red pen connected to one of the pins, and the black form to measure the other two pins are on the voltage display, then this transistor is NPN transistor, and the red Pen is connected to the foot of the base of the transistor B, the above method test when the black table of the multimeter one of the foot voltage is slightly higher, Then the PIN is the emitter e of the transistor, and the remaining low voltage pin is the collector C.

Another method is to use HFE block to judge. After determining the base and tube of the transistor, the base of the transistor is inserted into the LO value measurement hole according to the base position and the tube type, the other two pins are inserted into any two of the remaining three measuring holes, observe the size of the data on the display, find the collector and emitter of the transistor, swap the position and then measure again, Observe the size of the display value, repeated measurement four times, comparative observation. The largest one of the measured values, is the transistor's current amplification factor Lou, the opposite of the socket electrode is the collector and emitter of transistors.

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 pole
As you know, transistors are semiconductor devices that contain two PN junctions. According to the two PN junction connection method, can be divided into NPN type and PNP type two different types of transistors, Figure 1 is their circuit symbol and equivalent circuits.

Test transistor to use the Avometer ohm block, and select the Rx100 or rx1k stop. Figure 2 shows the equivalent circuit of the avometer ohm block. The figure 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 (see Figure 1, Figure 2 is not difficult
second, PN Junction, fixed tube type
After finding the base of the transistor, we can determine the conductive type of the tube based on the direction of the PN junction between the base and the other two electrodes (Figure 1). 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 arrow, deflection large
Find the base B, the other two electrodes which is the collector C, which is the emitter e? At this point we can determine the collector C and emitter E using the method of measuring the penetration current ICEO.
(1) For NPN transistor, the measuring circuit of the penetrating current is shown in Figure 3. According to this principle, with avometer black, red pen to measure the polarity between the positive and reverse resistance rce and Rec, although the two measurements of the multimeter pointer deflection angle is very small, but carefully observed, there will always be a slightly larger deflection angle, the current flow must be: Black-→c pole →b pole →e pole → Red pen, The current flow is exactly the same as the arrows in the transistor symbol ("Straight arrow"), so at this point the black-out pen must be collector C, and the red pen must be the emitter E.
(2) for the PNP type transistor, the principle is similar to the NPN type, its current flow must be: Black →e pole →b →c pole → Red pen, its current flow is also the same as the arrow in the transistor symbol, so at this time the black pen must be the emitter E, the red pen must be connected to the collector C (see Figure 1, Figure 3).
four, not to be measured, moving mouth
If in the "straight Arrow, deflection large" measurement process, if the reversal of the two times before and after the deflection of the measurement pointer 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. The human body plays the role of DC bias resistance, the purpose is to make the effect more obvious.

using a digital multimeter to determine the transistor pin (illustrated tutorial)

Now Digital multimeter is a very popular electrician, electronic measurement tools, its ease of use and accuracy by the maintenance personnel and electronics enthusiasts love. But a friend would say that when measuring certain parts, it is not as good as a pointer-type multimeter, such as a transistor. I think the digital multimeter is more convenient when measuring transistors. Here are some of my own experience, I usually judge the small transistor devices. We may try to see if it is good or not, and if you have any comments or questions, please send me a letter.
There are some BC337 transistors on hand, assuming it is a PNP or NPN tube.

We know that the inside of a transistor is like a combination of two diodes. The form is like the image below. The middle is the base pole (b-pole).

First we need to find the base and determine if it is PnP or NPN. As the figure shows, the base of the PNP tube is the common denominator of two negative points, the base of the NPN tube is the common denominator of two positive poles. At this point we can use the digital multimeter diode file to test the base, see Figure 3. For PNP tubes, when the black pen (the negative of the battery in the table) is on the base, the red pen is usually a smaller reading (general 0.5-0.8) with a small difference when measuring the other two poles, such as a larger reading (typically 1) when the pen is reversed. For NPN tables, the Red pen (even the positive battery in the table) is attached to the base. From Figure 4, Figure 5 can be learned that the BC337 on hand is an NPN tube, the middle of the pin is the base.

Figure 30,000 diode measurement file with table

Figure 4 Judging the B-pole and tube type of the BC337 (1)

Figure 4 Judging the B-pole and tube type of the BC337 (2)

After finding the base and knowing what type of pipe it is, it is possible to judge the emitter and collector. If using a pointer multimeter to this step may be used to two hands, and even friends will use the tongue, can be said to be quite troublesome. The use of the digital table of the three-Beecher HFE file (HFE measurement transistor DC magnification) to test the more convenient, of course, you can also save the above steps directly with the HFE to determine the pin polarity of the transistor, I myself think or add the above steps convenient and accurate some.

The multimeter to the HFE gear, BC337 Humble to NPN small hole, b pole to the above letter B. Reading, then turn it upside down another two feet and then read. The large reading of the polarity on the table above the letter, then to the letter to recognize the BC337 c,e pole. Learned, the other transistors are just like this, convenient and fast.

Figure 50,000 using the hFE file on the table

Figure 6 Judging the C,e pole

Figure 7 Judging the C,e pole