First Up Alarms

Hi ,

I was going through one of the decently writen code where i saw a routine called first up alarms.
There is one more seperate routine dealing with alarms ,then what is this firstup alarms ?
First up alarms are not used anywhere in program.may be they are used in SCADA alarms.

I want to know how SCADA ,PLC watchdog timer is implemented.
How do we check the SCADA communication stauts in PLC.


With Regrds
SCAN.PLC

Ok, firstly

Here is a list of SCADA manufacturers:

http://www.automation.com/sitepages/pid212.php

and here is a list of PLC manufacturers:

http://www.automation.com/smc/plugin/search.php

How are we supposed to guess from that list which 2 you are talking about ?

Hi ,

I believe it is irrelevant to manufacturer.
I want to know the general concept behind firstup alarms
and a watchdog implementation for SCADA-PLC Communications.

Any way here is the hardware i am talking about.
SCADA : RSVIEW 32
PLC:CONTROLLOGIX


SCAN.PLC

Not sure, its quite common though for alarm handling to be written in a manner where any subsequential alarms are suppressed in order to only diaplay one alarm.

Therefore you don't cloud the issue with nuisance alarms and only have the original fault shown.

Maybe this is what it does.

If i get an error between Citect and the PLC i get an automatic hardware alarm, i dont have to program this it just happens, it looks after itself.

Citect has no such thing as firstup alarms either.

Therefore i think you may be mistaken in thinking it is irrelevant to manufacturer.

You would normally check the PLC communication status with the scada

if you are using an OPC server- then check the raw values against the tags in the server itself- if they don't show here then the PLC has dropped coms

Sometimes you can use an event to drive alarms. Say you have 1028 alarm coils (bits) in a PLC program. The SCADA could run an event on CHANGE of any these bits to generate an alarm.

Sometimes it is necessary to force the SCADA to run this routine on startup of the SCADA to initially read the values of the bits and refresh the alarms. (I usually do this with an initialisation script) However you say the block is in the PLC so who knows.

Do you have a copy of the software design specification for your machine? I assume not but that would be the place to look.

Cheers

A first-out is used to detect the first alarm that came in since the last reset, event, etc. It is a good trouble shooter. However, it will not work properly if 2 or more alarms ring in at the same scan.

Hre is my logic for a Logix system. All alarms bits must be latched to work properly