Factory Talk data log question

jimdi4

Member
Join Date
Aug 2004
Posts
108
I am using the Factory Talk data log and in the setup the max data log points is 300,000. I want to monitor only 6 data points. How do I determine the length of time my trend will acquire data for lets say at a sample of all 6 data points every 10 ms? (lets say in total minutes)

Im not sure I understand the data log feature...:eek:
 
You are aware that you will not be able use an HMI application in order to acquire data and log it at I/O "quality" sample rates, don't you?
I would set a more realistic goal such as 500ms triggers.
And then if you want to be able to comprehend the 500ms logged data I would log it for a maximum of one hour which will give you 14400 samples.
The longer the sample rate the longer time intervals you will be able to cover, however, remember that the log is a graphical representation (vs. time)of the recorded values and not a classic database container.
There are dedicated software applications specifically designed to implement this kind of tasks; a FTVS application is an HMI (Human Machine Interface)application and not a Database server.
 
Last edited:
You are aware that you will not be able use an HMI application in order to acquire data and log it at I/O "quality" sample rates, don't you?
I would set a more realistic goal such as 500ms triggers.
And then if you want to be able to comprehend the 500ms logged data I would log it for a maximum of one hour which will give you 14400 samples.
The longer the sample rate the longer time intervals you will be able to cover, however, remember that the log is a graphical representation (vs. time)of the recorded values and not a classic database container.
There are dedicated software applications specifically designed to implement this kind of tasks; a FTVS application is an HMI (Human Machine Interface)application and not a Database server.


Abosolutlely!!....This would be sampled via my laptop...

the reason for the sample rate is to not miss any event changes between plc scans; its important to pick up any changes between scans.
 
To exactly answer your question though:
300000 samples at 10 ms = 3000 seconds = 50 minutes
I would not expect updating the log in less than 250 ms though (your actual sample rate will be 250ms at its best).
Even if running on your laptop, FTVS still is an HMI application
 
To exactly answer your question though:
300000 samples at 10 ms = 3000 seconds = 50 minutes
I would not expect updating the log in less than 250 ms though (your actual sample rate will be 250ms at its best).
Even if running on your laptop, FTVS still is an HMI application

So as I understand this the 6 data points that i am setting up for scan don't get subtracted from the 300000. I can have 20 tags in the data log, and the whole log is not depended on the number of tags. The 300000 size chunk is the log size.

The 250 ms will be way too slow if i expect to be capturing event changes between PLC scan times...I just went online with the PLC540 I am using and the max scan time is 26 ms...and the last overall scan time is 10 ms. So it may appear this won't work for what I intended....🤞🏻:cry:

any other ideas, suggestions? We are also working on a separate PLC, Clogix that will monitor the PL5 and capture data hardwired though..My method or what I was trying to achieve was less evasive....
 
I see where you are standing, sympathize, however, like I have stated within my first post, any HMI application is running at "snail" speeds when compared to CPUs scantimes or Logix I/O updates; a 500ms "response"is pretty much what to be expected from any HMI application, especially when using a (Maximum!)250kbps baudrate communications protocol like DH+.
In order to implement the I/O "quality" sample rates data logging you will need to invest serious $$$...Ethernet (Ethernet/IP) and a dedicated Historian (such as FT Historian SE)Database Server software/hardware is what I would look into.

http://www.rockwellautomation.com/rockwellsoftware/data/historian/historianse.html
 

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