313C Siemens plc counter input

[orense]

Hello everybody.

I have got a tanker where we have a 313C running the safety system on the propulsion engine. The engine has a pick up which is a proximity switch wired to the counter input on the plc. It is reading the rpm of the engine.

sometimes it is showing strange values which can not be correct. When I check the module information buffer, I got the meassage which is in the attached document.

Has anybody seen that message before:
"Modue problem or maintenance necessary", I am thinking that might make problems for the rpm reading.

Thanks for any answer...

brg
Andreas

 

[dchartier]

Hello Orense;
Until the diagnostic buffer can access the right tools in the PLC, information is sometimes sketchy.
First thing would be to insert an OB82 in your CPU, as requested by the diagnostic info you posted. ThisOB will be called when the situation arises and will lod a lot more details in the diagnostic buffer on the problem encountered.
To do so, go to the blocks folder of your program, right-click, Insert New Block, select OB and name the new nlock OB82. Then download it to the CPU (no program necessary in the OB if all you need is extended diagnosis).
The next time the module encounters a fault of the same type you will be better prepared to understand the cause of the error.
Hope this helps,
Daniel Chartier

 

[orense]

Thanks

Thank you for the answer, I will try to insert the OB.
Only one more thing, when you mention the following:

"Then download it to the CPU (no program necessary in the OB if all you need is extended diagnosis)"

When you say that all I need is extended diagnosis, what does that mean? Is it something I need to program?


brg
Andreas

 

[dchartier]

Hello Orense;
Sorry if I was not clear enough the first time.
No, do not program any code in OB82 if all you need is extended diagnostics on the event that called the OB82 (here, a diagnostic fault on a module). The presence of OB82 in the CPU's memory is sufficient for the diagnostic buffer to collect information on the fault, when it appears.
Code is programmed inside the OB82 (and other diagnostic OBs) for further provcessing or treatment: logging the date and time of the event in the PLC; calculating the duration of the event; setting a diagnostic bit in the program; calling a block you heve programmed to take over when the fault appears.... The code has to be as short as possible, so the diagnostic OB interrupts the processor for as short a time as possible.
Hope this helps,
Daniel Chartier

 

[orense]

Thanks

Ok,

got it now.
will go ahead and implement as soon as possible





andreas