The emitter and collector of the transistor are measured by testing

Connect the red test lead to the base and the black test lead to the other two pins in succession. If the overflow symbol "OL" or "1" is displayed twice, swap the test leads for measurement, that is, connect the black test lead to the base and the red test lead to the other two pins. If the displayed values ​​are all greater than 0.400V, it indicates that the transistor being measured is a silicon PNP type. At this time, the pin connected to the red test lead with the larger value is the emitter.

During the measurement process of the digital multimeter, if the displayed values ​​on the screen are all less than 0.400V, the transistor being measured is a germanium tube.

3. Detection of several parameters of transistor

3.1 Measurement of large coefficients

hFE is the DC current amplification factor of the transistor. The hFE of the transistor can be easily measured with a digital multimeter or a pointer multimeter. Set the digital or pointer multimeter to the hFE position. If the transistor being tested is an NPN type tube, insert the pins of the tube into the corresponding jacks of the NPN jack (if the transistor being tested is a PNP type tube, insert the pins of the tube into the corresponding jacks of the PNP jack). At this time, the display will show the hFE of the tube being tested. The schematic diagram of measuring the transistor amplification factor with a multimeter is shown in Figure 6.

Figure 6 Schematic diagram of multimeter measuring transistor amplification factor

3.2 Differences between Germanium Transistors and Silicon Transistors

The resistance block of a pointer multimeter cannot read the terminal voltage of the diode intuitively, and of course it cannot directly read the terminal voltage between the poles of the transistor. This makes it difficult to judge whether the voltage drop between the poles of the transistor is 0.60~0.70V or 0.15~0.30V, but it can be judged based on experience.

If you measure the resistance between B-E and B-C of the transistor (using the R×1k block or the R×100 block), and the pointer falls within the range of ⒛0~300Ω, it can be determined to be a germanium tube; if the pointer falls within the range of 800~1000Ω, it can be determined to be a silicon tube.