1) Measure the coil resistance Use the ohm gear of a multimeter to measure the DC resistance at both ends of the relay coil, which is the coil resistance.
2) Measure the pull-in voltage and release voltage Select a 0-30V regulated power supply and connect it according to Figure 2.

Adjust the voltage of the regulated power supply from low to high. When you just hear the "click" of the relay's moving iron core (armature), write down the voltage value indicated by the voltmeter, that is, the pull-in voltage of the relay. Then reduce the voltage of the regulated power supply in the opposite direction, and when you hear the sound of "click" being released from the moving iron core, write down the voltage value indicated by the voltmeter, that is, the release voltage of the relay. Multiplying the measured pull-in voltage by 1.3 to 1.5 is the rated working voltage of the relay.
1. The DC resistance of the coil refers to the resistance value of the coil measured by a multimeter.
2. Rated working voltage or rated working current, which refers to the voltage or current value of the coil when the relay is working normally.
3. Pull-in voltage or current, which refers to the minimum voltage or current when the relay generates pull-in. If only the pull-in voltage is applied to the coil of the relay, the pull-in at this time is not reliable.
4. The release voltage or current refers to the voltage value when the relay changes from the pull-in state to the release state when the voltage across the relay decreases to a certain value. The release voltage is much smaller than the pull-in voltage. Generally, the release voltage is about 1/4 of the pull-in voltage.
5. Contact load refers to the voltage and current value that the contacts of the relay can withstand when switching.