Most recent data displayed on our Real Time Trends are 50 seconds old.
Is this latency to be expected?
I haven’t seen it quite that bad before…
Is your data being stored/retrieved using the historian?
Have you checked the delay between the client and gateway, and between the gateway and database?
Synchronize your Clients and Gateway and Database clocks.
This is Easy Chart displaying R/T data.
Watching PLC and HMI interaction: Latency between PLC / HMI is ~ 1+ seconds.
Multiple Clients, including my (remote) development computer show the same symptom.
Not sure what you mean by synchronizing Gateway and Client clocks?
Do you mean at the operating system level?
Does a difference in time setting between computers really affect display of R/T chart?
Thank you for the response,
Forgot to state:
The R/T display shows 50 seconds of blank space between right edge and first trace. Scaling the duration changes the width of the gap but the actual delay remains the same,
Yes.
And yes.
The OS clock at the client is used to create the date bounds for the chart. If the clock is wrong, it won't match the data recorded.
Since you have the problem on all your clients, the gateway’s clock is probably the culprit.
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Good call there, pturmel!
Gateway computer time was set, but sync not enabled.
Somehow, somewhere, gateway clock was off by 50 seconds from the rest of the world.
Changed Gateway PC time and all is well.
I don’t understand why or how. Seems to me the gateway records, then delivers the data, so any time discrepancy should carry through. But it does not …
Thank you
regards
GF
I have a similar problem with a new installation on version 8.1.
The gateway time is 30’ish seconds ahead of the Development/Test client.
I’ve tried syncing both to time.windows.com but there is always an offset between the machines
The easy chart displaying 3 only realtime tags is confusing.
with the gateway leading by 30 seconds, the client displays “Realtime” data from 30 seconds ago.
i.e. at gateway time 13:00:00 reads value X, client time is 12:59:30
at gateway time 13:00:30 reads value Y, Client Time is 13:00:00 - chart displays value X
How do you get a chart to display actual realtime data.
Need this for tuning and commissioning control loops.
Is it possible to set the charts sync to Gateway Time so that “Realtime” display is always Realtime?
Typically in web applications - and I assume that Ignition works the same - the server (gateway) will assemble a dataset consisting of timestamps and data points and present this to the (Development/Test) client which renders the chart based on it’s own internal clock.
The proper solution would be to fix your time sync issue.
A hack solution to get you through commissioning could be to change the easy chart to manual mode, enable polling and configure Ignition to automatically update the End Date property e.g. once per second. But I suspect that it would still be easier to just disable the time sync on the client and manually set the time to be the same as the gateway just until you have time to get IT to fix the time sync issue.
Fix your time infrastructure. Use a local NTP server and have your local DHCP server include option #42 to have your clients automatically pick it up.