RS5K Alarm FB and deadband

Greetings,
I'm bringing a Process Variable into an ALARM function block and using the L LL H HH parameters for alarming on RSViewSE.
The problem I'm having is setting a deadband/filtering the process variable input. I'm getting alot of nuisance alarms because the process variable is teetering around my alarm setpoint.
How can I set a deadband for my Lo LoLo Hi HiHi alarms or maybe filter the input?


Also When PV is tettering around alarm setpoint...In RSViewSE an alarm line pops up on the AlarmInfo page when a point goes into alarm and then another alarm line popsup indicating that the point is "out of alarm". It doesn't take long to generate a large volume of alarms (for the same point) on my AlarmInfo Window.
Is there a setting I can set such that the "out of alarm" alarm line doesn't display on the AlarmInfo page? I'd like to see the existing "In alarm" alarm line just change color/stat when it becomes an inactive alarm.

Any help would be greatly appreciated.
Thanks
Modicon2

The Alarm Block in RSL5k does have a deadband value that defaults to 0. You can enter any floating point value to provide a deadband on the alarm points, either in the configuration dialog, or if you check the box to expose the input, you can feed it a source, or you can write directly to the location in the ALARM Tag (ALM_01.DeadBand).

If you need filtering, you can either apply it on the analog input channel at the module, or use one of the FBD Filter blocks (probably low-pass in your case), or use a simple, but effective one that has been posted here several times:

Filtered_Val = Filtered_Val + (Raw_Val - Filtered_Val) / Filter_K

Try different values of the constant Filter_K to get your desired filtering level.

About View and it's display of alarming, well, it's doing what it should really. You might want to be looking at only the ACTIVE ALARMS, rather than the running history of the AlarmDB.

Or, (which is a method I usually prefer), Latch alarms in the PLC, and have View clear the latches via an acknowledge.

follow up

Thanks for the reply. According to the description, this deadband is only for the HiHi & LoLo alarms. What about the Hi & Lo?

Hrm.... I'd have to check, I thought it applied to all of them. The range limit on the deadband is such that it must be set within the HiHi to LoLo range, or the block will trip the "Deadband Invalid" error state. There is a seperate deadband for the rate of change alarming.

Sorry I'm not more certain. If all else fails, and you are using analog inputs, just use the alarming on the input channel. I know that deadband applies to everything.

follow up

Thanks Again for your replies!

My inputs are coming through a Flex AI module (1794-IE8). I don't beleive that it has the ability to filter or deadband at the channel level. I'll have to play around with it some later, probably tommorrow.

Thanks Again!