How to judge the quality of 12vdc relay

There are many types and styles of 12vdc relay. 12vdc relay is mainly used for control loop (input loop) and controlled loop (output loop); the nature of work is to use lower voltage and smaller current to control higher voltage and larger current A kind of "transition switch". The picture below shows the physical picture of part of the 12vdc relay:

Here we use 12vdc relay, which is a relay mainly used in automatic control circuits, using a set of control signals to control one or more sets of electrical contacts.

The detection method of 12vdc relay mainly uses the following simple methods.

①Use a multimeter to measure the DC resistance of the coil of the 12vdc relay to detect different types of relays. The size and structure of the relay are different, and the DC resistance of the coil is different. You can judge whether the 12vdc relay is normal by detecting the resistance of the coil's DC resistance . However, this method cannot detect whether the coil has a partial short-circuit fault.

②The detection of the contact resistance of the 12vdc relay contact uses the R×1 block of the multimeter, and the two test leads are connected to the two pins of the normally closed contact respectively, and the resistance value should be zero ohms, and then connect the two test leads to the normally open On the two pins of the contact, the resistance value should be infinite ∞, then the relay is energized to make the armature act, turning normally closed to open, and normally open to closed, and then use the above method to detect the resistance value Just the opposite of the initial measurement, it indicates that the contact is in good condition. If the resistance value measured by the multimeter is a finite value when the contact is closed, it indicates that the contact is faulty, or the contact is oxidized, and you need to continue testing before it can be used.

③Detection of 12vdc relay release voltage and release current; this method is just the opposite of the above method. After the power is turned on, the contact is closed, and then the voltage is slowly lowered. At this time, its pull-in current is also slowly When the armature is released, the value on the voltmeter and ammeter is the release voltage and current value of the 12vdc relay. If the measured release voltage is less than 10% of the pull-in voltage, it means that there is a short circuit in the 12vdc relay or a fault caused by other reasons. It is also possible to check the 12vdc relay with a 12V DC bulb.