Testing methods for relays

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This post was last edited by shrien on 2018-7-4 08:33. A relay consists of a coil and a set of contacts; there are various types of coils available. In circuit diagrams, a relay coil is represented by a rectangular symbol, and if a relay has two coils, then two rectangular symbols are drawn side by side. At the same time, mark the textual symbol “J” for the relay inside or next to the rectangular box. There are those with outsourcing and those without; the coils should all be placed separately in dedicated containers. If they collide and interconnect, breaking them apart can cause the wires to snap. The following is the testing method: To measure the coil resistance, a multimeter set to the R×10Ω range can be used to determine the resistance value of the relay coil, thereby checking whether there is an open circuit in that coil. To measure the contact resistance, use the resistance setting on a multimeter to check the resistance between the normally closed contact and the moving contact; this resistance value should be 0 ； The resistance value of the normally open contact and the moving contact is then infinite. This allows one to distinguish which is a normally closed contact and which is a normally open contact. Measure the attraction voltage and attraction current. Obtain an adjustable voltage regulator and an ammeter, apply a voltage to the relay, and connect an ammeter in series in the power supply circuit for monitoring. Gradually increase the power supply voltage, and when you hear the relay engage, note down the voltage and current at which it engages. For accuracy, you can try it several times and take the average. Measuring the release voltage and release current also involves connecting the test as described above; after the relay engages, the supply voltage is gradually reduced, and this process can be repeated several times to obtain the average release voltage and release current. Under normal circumstances, the release voltage is around 10~50% of the holding voltage. If the release voltage is too low (less than 1/10 of the holding voltage), it cannot function properly, which poses a threat to the stability of the circuit and results in unreliable operation.