09-01-2006 09:16 AM
09-01-2006 12:18 PM
09-01-2006 12:45 PM
Hi Chad,
The relay closures occurred over a period of several weeks with perhaps a few hundred closures per coding cycle. So shutdown before the count being written to nonvolatile memory is clearly not the reason for the loss of the count.
As far as testing the contact resistance, I was thinking about a fixture that would present a load (several 10's of milliamps?) and comparing the applied load to the measured load. But, like you said, a relay can fail at any time.
You didn't come right out and say it, but it does sound like there is no way to reset the closure count in the non-volatile memory. Is this correct? Do users replace the relays based on closure count? Or do they do it upon noting a relay failure?
- les
09-01-2006 01:14 PM
Hi Les Bartel,
You are correct in stating the loss of relay count still does not have an explanation. I cannot explain what might've happened in this case, as there have been no reported incidents of such a scenario in the past. You are the first as far as I know. Perhaps someone else has had this experience and will post as well.
There are several methods to measure path resistance. The one you propose is exceptable, and could be relatively easy to automate.
As far as resetting the count, you can perform a reset using the Switch Soft Front Panel. Under File->Relay Maintenance, you can reset and/or edit the relay count stored in non-volatile memory. Although it depends on the application, most users will replace a relay upon noting a failure. Relay lifetimes are not exact, as a lot can play a part in how long a relay lasts. I've known several users in the past who will use one particular relay until it reaches a count limit. Then, they change to using another relay of that same module.
Let me know if you have further questions!
Chad Erickson