Static REAL Value Capture

[riggs33x]

Hi all,

Let's say we have a nice real (analog) value that has already been scaled with an SCP in Studio5000.

Is there a slick method to capture/notice when this value has become static (non moving, sensor failure, etc.) without using some Mov instructions to move numbers and timers around.

I want to be able to check on this real value (constantly measuring and changing reported values as it weighs material == it's a scale) say every 60 seconds or so; then, if the value isn't changing (has become static), I can make myself some alarms and so on.

Thanks,

 

[Steve Bailey]

You can check for an open wire or a maxed-out signal without using a MOV instruction, but to check for data changes over time you have to capture and hold a value for later comparison and that implies a MOV or COP type of instruction. What is your objection to using the obvious tool available to do the task?

 

[Ken Moore]

You might be able to use the ALM function block and use the Rate of change alarms, if ROC is true, then rate has changed.

 

[dmroeder]

Still uses timers/mov but is concise.

NEQ CurrentVal OldVal TOF ChangeTimer 60000 0 MOV CurrentVal OldVal

That works in my head. The timer should always be done if the value is changing because a TOF goes DN on transition to True, will go False after not true for the time period. You could hide the code in an AOI, then just provide the analog value.

 

[janner_10]

KISS.

No need to re-invent the wheel, if it's not changed in whatever seconds - sound the alarm.

 

[mylespetro]

Still uses timers/mov but is concise.

NEQ CurrentVal OldVal TOF ChangeTimer 60000 0 MOV CurrentVal OldVal

That works in my head. The timer should always be done if the value is changing because a TOF goes DN on transition to True, will go False after not true for the time period. You could hide the code in an AOI, then just provide the analog value.

This seems to me like the quickest and simplest way to do it programmatically, and having it in an AOI would be nice as well

 

[JeremyM]

Presumably you’re scaling and filtering raw data?

Monitor the raw data for its noise.

One (good) reason to max the channel resolution wherever possible.