Three test methods for electromagnetic relays

There are many types of relays, and there are more than a dozen types classified only according to the working principle or structural characteristics of the relay. However, in amateur production and regular applications, electromagnetic relays are more exposed.
The following briefly talk about the testing method of electromagnetic relay:
1. Measuring the coil resistance: the resistance value of the relay coil can be measured with the multimeter R&TImes; 10Ω gear, so as to judge whether the coil has an open circuit phenomenon. The resistance value of the relay coil has a very close relationship with its working voltage and working current, and its working voltage and working current can be calculated by the resistance value of the coil.
Three test methods for electromagnetic relays, do you know?
2. Measuring contact resistance: Use the resistance profile of a multimeter to measure the resistance of normally closed contacts and moving points. The resistance value should be 0. If the resistance is large or unstable, it means that the contacts are in poor contact. The resistance value of a point is infinite. If there is a resistance value, it is contact adhesion. From this, it can be distinguished 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 regulated power supply and an ammeter to input a set of voltage to the relay, and connect an ammeter in the power supply loop for monitoring. Slowly increase the power supply voltage. When you hear the pick-up sound of the relay, write down the pick-up voltage and current.
Measure the release voltage and release current: It is also connected to the test as described above. When the relay is closed, the power supply voltage is gradually reduced. When the relay releases sound again, write down the voltage and current at this time. Under normal circumstances, the release voltage of the relay is about 10-50% of the pull-in voltage. If the release voltage is too low (less than 1/10 of the pull-in voltage), it cannot be used normally, which will threaten the stability of the circuit. The work is unreliable.