Electricians and welders are specialized occupations, and those engaged in related work must hold a certification. Special operations certificates need to be re-evaluated every three years. One certificate per person is required, and it is valid nationwide.

Exam format: personal reference, single person at a table, divided into theoretical and practical subjects, with full marks of 100 and passing marks of 80.

Enrollment Consultation: 18206863120 (WeChat same number)

Digital Multimeter and Analog Multimeter: Transistor Measurement Guide

Using a multimeter to measure the condition of transistors and determine their pins is a fundamental skill in electronics. Have you ever struggled to identify the pins of a transistor? There are digital multimeters and analog multimeters, both of which can be used for measurement. Below, I will demonstrate the measurement methods one by one.

1. Measuring with a Digital Multimeter

When using a digital multimeter for measurement, the “diode mode” is used. The red probe corresponds to the positive terminal of the battery, and the black probe corresponds to the negative terminal.

Transistors are classified into NPN and PNP types, and their internal structures differ. However, there is a PN junction between the B, C, and E terminals. When positive voltage is applied to the PN junction, it will conduct.

When measuring with a digital multimeter, current flows out from the red probe.

Measuring Transistors with Digital and Analog Multimeters

▲ NPN type, the B terminal connected to the red probe, and the black probe connected to C and E will conduct

If it is an NPN type transistor, when the B terminal is connected to the red probe and the C and E terminals are connected to the black probe, the PN junction conducts in forward bias, and the multimeter will display the conduction voltage. The conduction voltage for silicon transistors is generally around 0.7V.

▲ PNP type, the B terminal connected to the black probe, and the red probe connected to C and E will conduct

If it is a PNP type transistor, when the B terminal is connected to the black probe and the C and E terminals are connected to the red probe, the PN junction conducts in forward bias, and the multimeter will display the conduction voltage.

During measurement, we can first assume one of the terminals is the B terminal, then fix one probe on the assumed B terminal and touch the other two leads with the other probe.

Measuring Transistors with Digital and Analog Multimeters

If both measurements do not show conduction, you can swap the probes and measure again until the B terminal is found.

Measuring Transistors with Digital and Analog Multimeters

If the conduction voltage displayed during measurement is 0V, it indicates that the transistor has broken down and is damaged.

After identifying the B terminal, you can find the C and E terminals. Hold the B terminal and the assumed C terminal, then place the probes on the assumed C and E terminals. If it does not conduct, swap the red and black probes.

Measuring Transistors with Digital and Analog Multimeters

If it still does not conduct after swapping the probes, assume the other terminal is C, then place the probes on the assumed C and E terminals to measure.

Measuring Transistors with Digital and Analog Multimeters

2. Measuring with an Analog Multimeter

When using an analog multimeter for measurement, the “Rx10K” resistance range is used. If measuring with other resistance ranges, the needle may not deflect enough to be easily observed.

When using the resistance range of an analog multimeter, the red probe corresponds to the negative terminal of the battery, and the black probe corresponds to the positive terminal, meaning current flows from the black probe, which differs from the digital multimeter.

During measurement, we can first assume one of the terminals is the B terminal, then fix one probe on the assumed B terminal and touch the other two leads with the other probe.

If both measurements do not show conduction, you can swap the probes and measure again until the B terminal is found.

After identifying the B terminal, you can find the C and E terminals. Hold the B terminal and the assumed C terminal, then place the probes on the assumed C and E terminals, observing the needle deflection, and swap the probes to measure again.

Then assume the other terminal is C, and place the probes on the assumed C and E terminals to measure. Observe the needle deflection and swap the probes to measure again.

To determine the C and E terminals, four measurements are needed. The terminal where the needle deflects the most is the E terminal.

Measuring Transistors with Digital and Analog Multimeters

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Digital Multimeter and Analog Multimeter: Transistor Measurement Guide

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