How to use a multimeter to judge whether the solid state relay is good or bad
When we detect whether the solid state relay is good or bad, it is generally impossible to detect it with a multimeter. The correct detection method should be like this.
First of all, after the appearance inspection is complete, we can connect a 3V to 32V adjustable DC voltage source to its input control terminal. At this time, we need to observe whether the indicator light-emitting diode can glow normally. At this time, we should pay attention to the output terminal without connecting the load. , and do not connect to the power supply.
The second step is to operate like this: At this time, we can use the pointer multimeter RX1K to detect the output terminal resistance. If the input terminal control voltage UI<2.7V, the resistance value indicated by the multimeter should be infinite, in other words, the solid state relay The output terminal of the solid state relay should be non-conductive; we continue to increase the voltage. When the voltage increases to 3V, the resistance value of the multimeter is generally lower than 10 ohms, indicating that the output terminal of the solid state relay has been conducted.
The last step is the third step: After the tests in the first two steps are normal, we can connect the load and power supply. When the input voltage is 0V, the load does not work; when the input voltage reaches about 5V, The load will work. At this time, it means that the solid state relay is intact, otherwise the solid state relay is faulty and needs to be repaired.
On the housing of the AC solid state relay, the input terminal is generally marked with "+", "-" and "INPUT", while the output terminal is not divided into positive and negative, but some devices are marked with the word "LOAD". For DC solid state relays, the input and output terminals are generally marked with "+" and "-", and some devices are also marked with the words "IN" (input) and "OUT" (output) to show the difference.
When using a digital multimeter to identify the input and input terminals, you can use the diode file to test the forward and reverse directions of the four pins respectively, and the voltage value between a pair of pins must be measured in accordance with the law of forward conduction and reverse cut-off , that is, it displays "1.3~1.6V" when measuring in the forward direction, and displays the overflow symbol "1" when testing in the reverse direction. Based on this, it can be judged that these two pins are input terminals, and when measuring in the positive direction, a measurement of "1.3~1.6V" is displayed, the red test lead is connected to the positive pole, and the black test lead is connected to the negative pole. For DC solid-state relays, after finding the input terminal, the positive and negative poles of the output terminal are generally opposite to each other horizontally. It should be pointed out that some DC solid-state relays have protection diodes on their output terminals, the positive pole of the protection tube is connected to the negative pole of the solid-state diode, and the negative pole of the protection tube is connected to the positive pole of the solid-state relay. Pay attention to the correct distinction when testing.
