Detection of Unijunction Transistors

2.2.1 Determination of emitter E
Set the multimeter to R x 100 or R x 1k, connect the black probe to the assumed emitter, and the red probe to the other two poles. When two low resistances appear, the black probe is connected to the emitter of the unijunction transistor.

2.2.2 Discrimination of base B1 and B2
Set the multimeter to R100 or R1k, connect the black probe to the emitter, and the red probe to the other two poles. In the two measurements, the one with the larger resistance is the one connected to the B1 pole. It should be noted that the above method of distinguishing B1 and B2 is not necessarily applicable to all unijunction transistors. Some tubes have a smaller forward resistance between EB1. However, it is not particularly important to accurately determine which pole is B1 and which pole is B2 in actual use. Even if B1 and B2 are reversed, it will not damage the tube, but only affect the amplitude of the output pulse (unijunction transistors are mostly used as pulse generators). When it is found that the output pulse amplitude is too small, just swap the originally assumed B1 and B2.

2.2.3 Voltage division ratio test
Figure 5 is a simple method for measuring the voltage division ratio of a single junction transistor. In Figure 5, the multimeter is in the DC voltage range, the power supply voltage E = about 10 V, and the voltage meter reading is V, then V = V/E.

Figure 5 Measurement of voltage divider ratio of a unijunction transistor