Multimeter - Tips for Measuring Transistors
Usually we need to use R×1kΩ file, whether it is an NPN tube or a PNP tube, no matter it is a low-power, medium-power, or high-power tube, the be junction and cb junction should show exactly the same unidirectional conductivity as the diode, and the reverse The resistance is infinite, and its forward resistance is about 10K. In order to further estimate the quality of the tube characteristics, if necessary, the resistance gear should be changed for multiple measurements. The method is: set the R×10Ω file to measure the forward conduction resistance of the PN junction is about 200Ω; set the R×1Ω file to measure The forward conduction resistance of the PN junction is about 30Ω, (the above is the data measured by the 47-type meter, other models are probably slightly different, you can test a few more good tubes to summarize, so that you know what you know) If the reading is too large If there are too many, it can be concluded that the characteristics of the pipe are not good. You can also put the meter at R×10kΩ and measure again. For tubes with lower withstand voltage (basically, the withstand voltage of the triode is above 30V), the reverse resistance of the cb junction should also be ∞, but the reverse resistance of the be junction There may be some, and the hands of the watch will deflect slightly (generally not more than 1/3 of the full scale, depending on the pressure resistance of the tube). Similarly, when measuring the resistance between ec (for NPN tube) or ce (for PNP tube) with R×10kΩ file, the needle may be slightly deflected, but this does not mean that the tube is bad. However, when measuring the resistance between ce or ec with a file below R×1kΩ, the indication of the meter head should be infinite, otherwise there is a problem with the tube. It should be noted that the above measurements are for silicon tubes, not for germanium tubes. But germanium tubes are rare now. In addition, the so-called "reverse" is for the PN junction, and the directions of the NPN tube and the PNP tube are actually different.
