How to check the quality of Schottky diodes with a multimeter
1. Detection of two-terminal Schottky diodes
(1) Detect with a pointer-type multimeter. Put the multimeter in the "R×1" block to detect, the black test lead is connected to the positive electrode, and the red test lead is connected to the negative electrode. When normal, the forward resistance value is 2.5~3.5Ω, and the reverse resistance value is infinite. If the measured forward and reverse resistance values are both infinite or close to 0, it means that the Schottky diode has been opened or damaged by breakdown.
(2) Detect with a digital multimeter
Put the multimeter in the diode block and measure the forward and reverse resistance values of the two-terminal Schottky diode. When normal, its forward resistance value (the red test lead is connected to the positive pole) is 2.5-3.5Ω, and the reverse resistance value is infinite. If the measured forward and reverse resistance values are both infinite or close to 0, it means that the Schottky diode has been opened or damaged by breakdown, as shown in Figure 5-44.
2. Detection of three-terminal Schottky diodes
The three-terminal Schottky diode should first measure its common terminal to determine whether it is a common cathode-to-tube or a common anode-to-tube, and then measure the forward and reverse resistance values of the two diodes respectively. Now take the test of two Schottky diodes with common cathode and common anode as an example to illustrate the specific detection method. The pins are marked as 1, 2 and 3 respectively, and the multimeter is placed in "R×1' 'Do the following three-step test:
(1) Measure the forward and reverse resistance values of pins 1 and 3. If it is infinite, it means that these two electrodes have no unidirectional conductivity.
(2) Connect the black test lead to pin 1 and the red test lead to pin 2. If the measured resistance value is particularly poor, then switch the red and black test leads to measure. If the measured resistance value is 2.5~3.5Ω, then Note 2. The 1 pin has unidirectional conduction characteristics, and the 2 pin is positive and the 1 pin is negative.
(3) Connect the black test lead to pin 3 and the red test lead to pin 2. If the measured resistance value is infinite, then replace the red and black test leads to measure. If the measured resistance value is 2.5~3.5Ω, it means 2 , 3 pins have unidirectional conduction characteristics, and 2 pins are positive and 3 pins are negative.
According to the above three-step measurement results, it can be judged that the Schottky diode under test is a common anode pair tube, in which pin 2 is the common anode, and pins 1 and 3 are two cathodes. On the contrary, it is a common cathode pair tube.
