Averaging values with A Controllogix L61

440_Man · Jan 21, 2016

I have a process that is using a mV signal to control a PID loop. Currently, the mV signal is experiencing a +/- 1 mV noise. In this process, +/- 1 mV is a tangible change. I would like to take a sample of ten mV readings every second, then use the average of those ten readings to control my process. I am fairly new to ControlLogix, so detailed help with the instructions would be appreciated.

thanks,
440_Man

IF4XOF2F/A analog card
Digital filter for the mV input is set at 1000 milliseconds
RTS for IF4XOF2F/A is set at 25 ms
PID loop is in a periodic task set at 100 ms time period
Report Post

Paullys50 · Jan 21, 2016

Search the forums for 'Digital Filtering'

To get you started:
http://www.plctalk.net/qanda/showthread.php?t=91108&highlight=digital+filtering

Lovell · Jan 21, 2016

If you have access to Function Block, I have used the LDLG instruction to do filtering. You can adjust the Lag parameter to get the desired result.

440_Man · Jan 21, 2016

Thanks for the reply Lovell, but I am looking for a ladder logic solution instead.

GaryS · Jan 21, 2016

what's wrong with using the AVE function
copy the data to an array with a FIFO load unload and then use the AVE

440_Man · Jan 21, 2016

Gary, Could you post some example code for this?

Mickey · Jan 21, 2016

That card is not made to measure mv. The resolution is probably your problem.

See PDF

Thermocouple input modules have mv ranges.

440_Man · Jan 21, 2016

Mickey, my range is from approximately 800 mV to as high as 1.500 volts.
Is there a better card for my application?

440_Man · Jan 21, 2016

Found the formula FV=FV+C(NV-FV) while digging through the forum. I will implement this and let the process run a few hours to see if this filter will work for me.

thanks for the help!

Mickey · Jan 21, 2016

440_Man said:
Mickey, my range is from approximately 800 mV to as high as 1.500 volts.
Is there a better card for my application?

A mv transmitter may be a better option, that would give you an input in the 4 to 20ma range or 0 to 10 volts etc.

440_Man · Jan 21, 2016

Thanks for the tip Mickey. I will look into that option.

Averaging values with A Controllogix L61

440_Man

Member

Paullys50

Lifetime Supporting Member

Lovell

Member

440_Man

Member

GaryS

Member

440_Man

Member

Mickey

Lifetime Supporting Member

440_Man

Member

440_Man

Member

Mickey

Lifetime Supporting Member

440_Man

Member

Similar Topics