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How to Measure UJT Using a Multimeter

Electricity is created by the flow of charged particles through metal wires. Electrical circuits consist of a number of components, such as resistors, capacitors and transistors. Of particular importance is the uni junction transistor, UJT, which is a semiconducting device that allows the switching and amplification of electrical signals. UJT devices can sometimes fail if they are exposed to current that's too high, so it's important to have a means to test them. A digital multimeter is a portable device that is capable of measuring voltage, current and resistance. It is fully capable of testing a UJT device.

Things You'll Need

Digital multimeter

Instructions

- 1
  Switch on the digital multimeter and select the resistance mode by rotating the dial on the front. Connect the positive red lead of the multimeter to the B1 terminal on the UJT and the negative black lead to the B2 terminal. The multimeter should display a high resistance of 4 to 10K ohms. Swap the leads around. The display should still show the high resistance. If a low resistance is shown in either of these measurements, the UJT is faulty.
- 2
  Connect the negative black lead to the E, or emitter, terminal, and the positive red lead to the B1 terminal. The multimeter should show a resistance of 100K ohms. Leave the negative lead on the E terminal and move the positive lead to the B2 terminal. The display should still show a high resistance. If a low resistance is measured, the UJT is faulty.
- 3
  Connect the positive red lead to the E terminal and the negative black lead to the B1 terminal. The multimeter should show a low resistance of around 100 ohms. Leave the negative lead on the E terminal and move the positive lead to the B2 terminal. The display should still show a low resistance. If a high resistance is measured, the UJT is probably faulty.

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