Introducing the method of using a multimeter to identify the transistor/E pole

Usually we can easily find the base b of the triode, but which of the other two electrodes is the collector c and which is the emitter e? At this time, we can determine the collector c and emitter e by measuring the penetration current ICEO.

1. For a PNP transistor, use your fingers to hold the b electrode and the hypothetical c pole. Use our fingers to act as a resistor between the pins. Connect the black test lead to the hypothetical c pole, and the red test lead to the hypothetical e pole. Use a multimeter. Set the R×1K position to measure the resistance Rce between the two poles; then swap the assumed c and e poles and measure again. Although the deflection angle of the multimeter pointer is very small in the two measurements, if you observe carefully, there will always be a slightly larger deflection angle. At this time, the current flow must be: black test lead → e pole → b pole → c pole → red test lead. The flow direction is also consistent with the direction of the arrow in the transistor symbol, so at this time, the black test lead must be connected to the emitter e, and the red test lead must be connected to the collector c.

2. For the NPN transistor, use your fingers to hold the b electrode and the hypothetical c pole. Use our fingers to act as a resistor between the pins. Connect the black test lead to the hypothetical c pole, and the red test lead to the hypothetical e pole. Use the multimeter to test. Go to the R×1K range and measure the resistance Rce between the two poles; then swap the assumed c and e poles and measure again. Although the deflection angle of the multimeter pointer is very small in the two measurements, if you observe carefully, there will always be a slightly larger deflection angle. At this time, the flow direction of the current must be: black test lead → c pole → b pole → e pole → red test lead, so At this time, the black test lead must be connected to the collector c, and the red test lead must be connected to the emitter e.