How do you test relays?

[six el six]

1. How do you test relays to make sure they're good?

The ubiquitous Omron G6A-274P-ST-US for instance?

I mean you can't see the contacts so how do you know?

I'm attaching a data sheet for the this type relay.

Thanks,
six

[sluckey]

There are two problems you can have with a relay, assuming the energizing circuit is OK. The coil may fail to operate the contacts because it it open (check with ohm meter) or some mechanical problem. Or the contacts may fail to operate properly even if the coil is doing it's thing. First determine the contact arrangement. Then use your ohm meter. Check the contacts just like you would a manual switch.

For example, to check a DPDT relay...

Use an ohm meter to check for continuity between the common (C, or COM) contact and normally closed (NC) contact. Repeat for the other set of contacts. While you're at it, make sure ther is no continuity between the common and normally open (NO) contacts.

Now energize the relay using the proper coil voltage. Most times you can hear or feel the click as the relay operates. Now check for coninuity between the 'C' and 'NO' contacts. And make sure there is no continuity between 'C' and 'NC' contacts.

That's about all you can do to a small sealed relay.