Microllogix 1400 issue

Hello everybody,


we have in our power plant micrologix 1400 PLC installed with filter. The main task of these PLC is to:
1-Read via a one differential pressure transmitter the pressure before and after filtering.
2-Launches a cycle to clean filter.


The problem is sometimes (e.g after 1 month), the measurement of pressure jammed & set at one value ( e.g 100mbar) on the PLC, by reboot of PLC, the measurement of pressure refreshed and the issue is solved but temporarily.
Now, I am trying to find a definitive solution for that problem.



Would you please help me.

Can you post your code so we can help you out?

Some clarification would help.
How is the PLC reading the data (I.E. analog inputs, etc…)?
How are you reading the values (HMI, LCD screen, etc…)?

Hi

Just a while back I had a issue with a compact logix analog input something like you are talking about. I had some vsd that where starting and stopping from outputs in the plc. I had to seperate the 24v dc power supply to both and then the problem went away. I actually installed a second power supply to do this after checking the wiring, grounding etc etc
It was of those ones were I should not have had to do that but it worked and fixed my problem

Donnchadh

Hello Guys, first I want to thank you for your answers and second I am sorry for this delay.

Well:

- Coulombboy please find attached the code

- Firejo we are reading the values through PV 600

- Donnchadh I will try your proposition and as you see in the attached file the 24V is common.

Still pretty sparse on data however one thing I would do (when the problem is presenting itself) is go online with the PLC and see if the raw analog input data is fixed or changing. If the analog input (from the pressure sensors) is changing then look to see how that data is being provided to the PV. Is it being moved, scaled, etc…? If it is being manipulated before making it to the PV then is the data source the PV is reading fixed or changing? In other words start with the raw analog data and work your way back to the HMI and you should find where the problem lies.