[dpearson]

I am using a memkey that came with a gaging system that my company purchased a few years ago. Last year I added an automation system to the gage and am using a plc to trigger one of the memkey outputs by closing a relay output to simulate a button push. Every once in a while something happens that causes the memkey to lose its programming and go back to its default settings. I am looking for any help that can be provided. I have two units that both do the same thing.

Thanks for any advice.

[Lon]

Without sample code it's difficult to find out exactly what is happening. If the controller interfaced to the MEMKey has any code that implements a Default Reset command (H'11') then the relay closure you're using could be causing a power reset condition, or some other condition, that causes the controller to use that command.

Alternatively, the relay closure could be causing noise on the FM line that looks like a H'11', or binary '00010001'. If your PLC/relay closure is a common occurance then the noise could be a random appearing result. The way to test for this is to monitor the FM line with an oscilloscope and see if noise is present during the PLC/relay.

There are two tests that you can do if you don't have a scope, but do have control of the PLC.

1. Setup the PLC to constantly trigger the relay. If the problem is randomly generated by noise caused by this closure it should happen more often.

2. Setup the PLC to never trigger the relay. If the problem is randomly generated by noise caused by this closure it should never happen.

Lon