Digital Multimeter Test Method for Unidirectional Thyristors (SCR)
Unidirectional thyristor, abbreviated as thyristor (SCR), formerly known as silicon controlled rectifier, is a controllable rectifying component. Its circuit symbol is shown in Figure 1, where A stands for anode, K for cathode and G for gate.
Performance Identification of Unidirectional Thyristors
Unidirectional thyristor, abbreviated as thyristor (SCR), formerly known as silicon controlled rectifier, is a controllable rectifying component. Its circuit symbol is shown in Figure 1, where A stands for anode, K for cathode and G for gate.
① Electrode Identification Keep the red probe in contact with any one electrode, and touch the other two electrodes successively with the black probe. If a reading of 0.2～0.8 V appears for one electrode and overflow is displayed for the other, the electrode connected by the red probe is G. The electrode giving overflow when touched by the black probe is A, and the remaining electrode is K. If the measurement result does not match the above description, change the electrode for the red probe and repeat the steps until the correct result is obtained.
② Trigger Characteristic Test The diode mode of a digital multimeter can only supply a test current of approximately 1 mA, so it can only be used to check the triggering capability of low-power unidirectional thyristors. The operating procedure is as follows: Keep the red probe touching A, and connect the black probe to K. The meter shall show overflow (off state). Then, while maintaining contact between the red probe and A, briefly touch G with the red probe. The reading will generally drop below 0.8 V (the device turns on). When the red probe is removed from the gate immediately afterwards, the conducting state will be maintained. If the same result can be reproduced in repeated tests, the thyristor has sensitive and reliable triggering. This method is only applicable to devices with low holding current.
