Flow meter cycle Logging

I'm looking to install a Panelview Plus in order to log the totalized flows on a system. I will be using a CompactLogix L24 processor to count the pulses on the flow meter in order to show how much fluid has passed at each cycle. I know how to show that data, but don't know how to show a log of historic data.
We operate on a 20-second cycle time (typically), but it sometimes varies faster or slower, so just setting a 20-second sample rate wouldn't work well. Is there a way to make it only record the values when it receives signal from a specific trigger (i.e. limit switch)?

For historic data, you will have to fiddle in the logic. It all depends on how much data you want to look back on. Lets assume the data you are capturing is single value that can be captured by an Int or Dint. Make an array of FlowData of type Int/Dint or Real and give it length of say 32/64/128 depending on your need.

Make an index variable of type Int so that you have a variable FlowData[Index]. Start with Index=0. Whenever you capture the flow at defined interval move it to FlowData[Index] and increment it by +1. This will happen as as long as Index value is less than total length of the array you chose. i.e.


while Index < Arraysize

Move data to FlowData[Index]

Index = Index+1

When Index = arraysize -1

Index = 0

and on your Next cycle the oldest value will be overwritten.


On the HMI make numeric display fields starting from address FlowData[0] all the till the end or you can make a single field with the address FlowData[HMIINdex] with Next and Previous button that increment and subtract the HMI Index and display the subsequent value at that index on to the HMI.