Do you know the three testing methods of electromagnetic relays?

There are many kinds of relays, and there are more than a dozen types classified by the working principle or structural characteristics of the relay. However, in amateur production and conventional applications, we are more exposed to electromagnetic relays.

The following is a brief description of the test method of electromagnetic relays:

1. Measure the coil resistance: You can use a multimeter with the R&TImes;10Ω setting to measure the resistance of the relay coil to determine whether the coil is open circuit. The resistance of the relay coil is closely related to its operating voltage and current. Its operating voltage and current can be calculated through the resistance of the coil.

2. Measure the contact resistance: Use the resistance range of the multimeter to measure the resistance between the normally closed contact and the moving point. The resistance should be 0. If the resistance is large or unstable, it means that the contact is poor. The resistance between the normally open contact and the moving point is infinite. If there is a resistance value, it means that the contact is sticking. This can distinguish which is the normally closed contact, which is the normally open contact, and whether the relay is good (especially the used relay).

3. Measure the pull-in voltage and pull-in current: Use an adjustable voltage-stabilized power supply and an ammeter to input a set of voltages to the relay, and connect an ammeter in series in the power supply circuit for monitoring. Slowly increase the power supply voltage, and when you hear the relay pull-in sound, record the pull-in voltage and pull-in current.

Measure the release voltage and release current: Connect and test as above. After the relay is closed, gradually reduce the supply voltage. When you hear the relay release sound again, record the voltage and current at this time. Generally, the release voltage of the relay is about 10-50% of the closing voltage. If the release voltage is too low (less than 1/10 of the closing voltage), it cannot be used normally, which will threaten the stability of the circuit and make the work unreliable.