Dynamic Alarm Setpoint not Updating Quickly

Ignition
1

I am trying to use a Dynamic Setpoint to Trigger an Alarm and it does not update the setpoint as quick as I need it to.

Below is what i am doing.

  • I have a UDT for a Flow Meter and a UDT for a Combustor.
  • If the combustor is running I want to ensure that I have flow being measured by my meter, if I don't I want to trigger an alarm.
  • The setpoint on the flow rate tag is set to the following binging: if({[.]../Pad/ecd_run_status}>7,1,-10)
  • Basically if the Run status is greater than 7(Burning) the low flow setpoint should be 1, else -10(Not running so set it to an unattainable).
  • The issue is when I monitor all this on a custom display the run status goes to 15 but the setpoint doesn't change unless i restart the tag.
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2

Alarm bindings do not update dynamically. They are only evaluated when an event happens, which too late for setpoint changes.

For a robust solution, make the setpoint a separate memory tag, then use an expression tag to generate a boolean. Use that boolean for your alarm.

1 Like
3

Thanks! Before I create a bunch more tags, I could also bind the Enable/Disable feature of the alarm to the condition. And only enable the alarm if the equipment is in a running state. That seemed to be working quickly; however, it seemed to trigger my alarm cleared event state script every time it was re-enabled. Is there any workaround for this?

4

Same fundamental problem. That won't be evaluated with the timing you need.

5

Why not do this in the PLC as it can be evaluated more real-time and have more control than the HMI should have?

2 Likes
6

Even better. :100:

7

For some PLC models, changing or adding such alarms requires a reboot. This also requires updating each PLC, which is more convenient in UDT.

8

I don't know of any major PLC brand that cannot live add a generic tag and comparison logic to yield the desired boolean. The alarm definition would still be in Ignition on that boolean.

9

These are the PLCs I (and others should) avoid!

The only time I've seen analog alarms actually used in an HMI is when there's not a PLC involved like monitoring power equipment/HVAC equipment in datacenters.

10

It's really part of my job.
From the perspective of factory managers, many devices are provided and installed by suppliers. When managers want to monitor information that was not originally considered, they have to contact suppliers, which requires additional costs and, more importantly, time. We should avoid this situation, but it happens all the time.

11

Yeah it can be done in a PLC and we do most alarming that way. However, for this alarm in particular we need to do it for 120 different facilities and there is no reason for it to be a local alarm. It is for our Air Quality team to look for potential issues from a high-level standpoint. It was quicker to roll this out in ignition in a UDT. I appreciate all the responses, and I have a path forward that will work. Thanks again everyone.