Why, when judging the electrodes of the crystal triode, can't it be measured through electrical barriers like a pointer analog multimeter?
Because different types of digital multimeters are electrically blocked, their open circuit voltage and short circuit voltage are only a few tenths of a microampere. Another is the digital multimeter provided by the digital multimeter as an example. The open circuit voltage of the 200 2 gear is about 0.54V, and the higher the gear, the lower the open circuit voltage. For example, the open circuit voltage of 2M 2 gear is about 0.49V. As for the short-circuit current, the 200 Q gear is about 0.6mA, and the higher the gear, the smaller the short-circuit current. For example, the short-circuit current of the 2MΩ gear is only a few microamperes, while that of the 2000MΩ gear is only a few tenths of a microampere. Another is that the test current provided by the digital multimeter is very small. When measuring the forward resistance of the crystal triode, it is higher than the measured value of the electrical resistance of the analog meter (such as the current of the MF47F analog meter x 1k block is about 1mA). Several times, even dozens, hundreds of times. Therefore, it is not suitable to measure and judge the transistor with a digital multimeter.
It is more appropriate to use the diode block to measure the PN junction resistance to judge the E, B, and C poles of the transistor, because the open circuit voltage and short circuit current of the diode block are relatively large. Taking VC9808+ as an example, the open circuit voltage of the diode block is about 2.7V, the short-circuit current is about lmA. When measuring, for the NPN tube, connect the red test lead to its "B" pole, and the black test lead to the other two pins respectively. Among the two measured numbers, the pole with a slightly higher value The "E" pole, the one with a lower value is the "C" pole. If it is a PNP tube, the black test lead is connected to its "B" pole, and the high data obtained is the "E" pole, and the low data is the "C" pole. For example: connect the middle pin (B pole) of C9018 with the red test lead, and connect the other two pins with the black test lead respectively, and two values of 726 and 734 can be obtained. Among them, 726 is the test value between B-C, and 734 is the test value between B-E.
In short, after the actual measurement test, the digital multimeter uses the diode block to test the E, B, and C poles of different types of transistors and has achieved accurate test results.
