Alarm when Analog Signal stops moving

[Ones_Zeros]

Hello,
I have a compact Logix plc and I have been task with configuring alarms into our SCADA when an Analog signal stops moving.

The analog signal normally should trend upward and if it would go out of replay and the signal would stop moving, how could I configure this state to trigger and output in the plc?

Then I could feed this into our SCADA as an alarm that something is wrong with this input and needs addressed.

Thanks

 

[Ones_Zeros]

Hello,
I have a compact Logix plc and I have been task with configuring alarms into our SCADA when an Analog signal stops moving.

The analog signal normally should trend upward and if it would go out of replay and the signal would stop moving, how could I configure this state to trigger and output in the plc?

Then I could feed this into our SCADA as an alarm that something is wrong with this input and needs addressed.

Thanks

Also when the analog signal stops could also mean a leak as well.

 

[Bit_Bucket_07]

Hello,
I have a compact Logix plc and I have been task with configuring alarms into our SCADA when an Analog signal stops moving.

The analog signal normally should trend upward and if it would go out of replay and the signal would stop moving, how could I configure this state to trigger and output in the plc?

Then I could feed this into our SCADA as an alarm that something is wrong with this input and needs addressed.

Thanks

1. Compare the value of the analog input to a tag called "AnalogValueLastScan".
2. If the two values are equal, start a timer. If the timer times out, set an alarm.
3. Move the value of the analog input into a tag called "AnalogValueLastScan" to initiate the next iteration of comparisons.

NOTE: You may want to create deadbands around the analog input value for your comparisons, if your analog input has some inherent drift.

 

[GaryS]

If this is a critical as you say then I would recommend that you install a redundant sensor feeding it in to a separate analog input modules in the plc.

Establish an allowable difference between the 2 sensor. The difference between the 2 inputs values exceed that value trigger an alarm.

That way a sensor or module failure will trigger an alarm.

I have done this for a number of systems and it has pay off for my clients



Create 2 Tags Labeled OLDINPUT_1 and OLDINPUT _2

Read in the 2 inputs and move then into the new tags

Next on a preset time read in the 2 inputs and compare them to saved values

If the new input values are not larger than the saved value then trigger an alarm

If the both the new values are larger than the saved values then move the new input values to the OLDINPUT tags

Repeat



Not you should always setup and trigger your alarm in the plc and then post and display them in the HMI

And in this case I would log these alarms so you have a history to look at.

 

[I_Automation]

Search for Anti-Stall Timer.

Run a timer for the preset of your alarm time.
Every scan see if the analog value is not equal NEQ the analog value you recorded last scan to a tag, if not equal then reset the timer. (If it has to raise then check if greater than GEQ)
Next record the current analog value to the last scan tag.
If the timer ever gets done you have an alarm condition

With an analog signal varying slightly every scan you probably have to programming in a tolerance or dead and range.

 

[MaxK]

Uhhh... “Beer_and_popcorn”

Bros, feel free to apply your algorithms to blue curve

I propose the following algorithm

Initial:
ancillary_variable : = measured_value – noise_amplitude (of course peak to peak amplitude)

on every scan:
IF
ancillary_variable < measured_value
THEN
ancillary_variable : = ancillary_variable + slope factor (of course slope factor per scan time)
ELSE
Alarm := true
END_IF

IF
measured_value – ancillary_variable < noise_amplitude
THEN
ancillary_variable : = measured_value – noise_amplitude
END_IF


it is obvious that the distribution mode is equal to half of slope factor

 

[Ones_Zeros]

Thanks guys for the feedback
I greatly appreciate it!