How to test relay using multimeter?
As an important component in electronic circuits, relay is widely used in automation control, communication equipment, household appliances and other fields. Its main function is to control large currents through small currents, thus realizing the automatic switching of circuits. However, relays may malfunction in long-term use, resulting in equipment not working properly. Therefore, learning to use a multimeter to test the status of a relay is one of the necessary skills for electronic engineers and hobbyists.
As a professional foreign trade company, MobikeChip is committed to providing customers with high-quality electronic components and technical support. This article will give you a detailed introduction to how to use a multimeter to test the relay, to help you quickly determine whether the relay is working properly.
The working principle and test significance of the relay
Relay is a kind of electromagnetic switch, usually composed of coil, contact, core and other parts. When the coil is energized, the magnetic field generated will attract the contacts to close or break, thus controlling the switching state of the circuit. The main parameters of a relay include coil resistance, contact resistance and operating voltage.
The significance of testing the relay is:
Determine whether the relay is damaged or not, so as to avoid the equipment not being able to operate due to relay failure.
Confirm whether the parameters of the relay meet the design requirements to ensure the stability of the circuit.
Understand the performance of the relay through testing to provide a basis for maintenance and replacement.
Preparation before testing
Before testing the relay, you need to prepare the following tools and materials:
Digital multimeter or analog multimeter (digital multimeter is recommended for higher accuracy).
The relay to be tested.
DC power supply (for powering the relay coil).
Connecting wires and clips (for connecting the circuits).
It is also important to know the pin definitions of the relay. Usually, the pins of a relay are labeled on the coil and contacts, e.g. “COIL” for coil, “NO” for normally open contact, “NC” for normally closed contact, “COM” for normally closed contact. “COM” means common contact.
Steps for testing a relay with a multimeter
1. Test coil resistance
Set the multimeter to resistance measurement (usually Ω), and contact the coil pins of the relay with the meter pen. Under normal circumstances, the coil resistance value should be between tens of ohms and hundreds of ohms. If the resistance value is infinity, it means that the coil is disconnected; if the resistance value is zero, it means that the coil is short-circuited. Both conditions indicate that the relay is damaged.
2. Test contact resistance
Normally closed contact (NC) test: Set the multimeter to resistance measurement, and use the pen to contact the “COM” and “NC” pins. When not energized, the resistance value of the normally closed contacts should be close to zero; after energized, the resistance value should be infinity.
Normally open contact (NO) test: use the meter to contact “COM” and “NO” pin. When not energized, the resistance value of the normally open contact should be infinite; after energized, the resistance value should be close to zero.
If the test result is not consistent with the above, it means that the contacts may be oxidized or damaged, and the relay needs to be replaced.
3. Test operating voltage
Connect the DC power supply to the coil pins of the relay and gradually increase the voltage until the relay operates (“click” sound is heard). At this time, the voltage value displayed on the multimeter is the operating voltage of the relay. If the difference between the operating voltage and the nominal value is large, it means that the relay has poor performance.
Precautions during the test
During the test, be sure to disconnect the power supply to avoid electric shock or damage to the multimeter.
When testing the contact resistance, make sure the relay is not energized to avoid affecting the test results.
If the working voltage of the relay is high, it is recommended to use insulated tools to ensure safety.
For sealed type relays, when it is impossible to test the contact status directly, you can judge indirectly through the external circuit.
Through the above steps, you can easily use the multimeter to test the status of the relay and quickly determine whether it is working properly. As an important part of electronic components, the performance of relays directly affects the operating effect of equipment. Therefore, it is very necessary to test and maintain relays regularly.
As a professional foreign trade company, MobikeChip is always committed to providing customers with high-quality electronic components and solutions. If you encounter any problems when testing or using relays, please feel free to contact us, we will be happy to provide you with technical support and service!
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