1. Measure the relay contact resistance

Use the resistance profile of the universal meter to measure the resistance of the normally closed contact and the moving point. The resistance value should be 0; and the resistance value of the normally open contact and the moving point is infinite. From this, it can be distinguished which is a normally closed contact and which is a normally open contact.

2. Measure the resistance of the relay coil

The resistance value of the relay coil can be measured with the universal meter R×10Ω, so as to judge whether the coil has an open circuit phenomenon.

3. Measure the pull-in voltage and pull-in current of the relay

Get an adjustable regulated power supply and an ammeter, input a set of voltages to the relay, and insert 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. For accuracy, you can try several times and find the average value.

4. Measure the relay release voltage and release current

The connection test is also like the above. When the relay pulls in, then gradually reduces the power supply voltage. When you hear the relay release sound again, write down the voltage and current at this time. You can also try several times to get an average release. Voltage and release current. Under normal circumstances, the release voltage of the relay is about 10~50% of the pull-in voltage. If the release voltage is too small (less than 1/10 of the pull-in voltage), it cannot be used normally, which will threaten the stability of the circuit.