Control System Time

Join Date
Jan 2009
Location
NH
Posts
505
Does anyone have any best practices on keeping good time on their control system? What equipment do you use? I realize the definition of 'good' is very subjective, but let's say for simplicity there are two cases:

1. We just install control equipment without dealing with time at all
2. We want some control over time, but there is no sub-ms precision requirement or anything like that. We just want the clocks on the controllers and SCADA to be reasonably close.

I am more interested in case 2 - I see GPS receivers, and other hardware we can buy. What about NTP? Any comments on using this? Does it work for you?

Thanks for your comments.
 
Does anyone have any best practices on keeping good time on their control system? What equipment do you use? I realize the definition of 'good' is very subjective, but let's say for simplicity there are two cases:

1. We just install control equipment without dealing with time at all
2. We want some control over time, but there is no sub-ms precision requirement or anything like that. We just want the clocks on the controllers and SCADA to be reasonably close.

I am more interested in case 2 - I see GPS receivers, and other hardware we can buy. What about NTP? Any comments on using this? Does it work for you?

Thanks for your comments.

We have used these a couple of times, NTP and are very good, can get its time source from GPS or radio (GPS is better)

http://www.timetools.co.uk/

There a are lots of options out there, just depends if all your devices are NTP capable and how much you want to pay.
 
Most of the automation products I use support NTP, and it works quite well. You do need an NTP server, but often this can run in the background on the same PC as your SCADA/HMI system. Usually, I've seen those hooked up to a master NTP server on the internet, but you don't really need that if your only goal is to just keep your system synced up.

I've used GPS units before as a time master, and they do work well, especially for systems in remote areas. They were perfect on some systems I did that controlled solar panels tracking the sun. Needed very accurate position and time info to be able to calculate exactly where the sun is in the sky.
 
robertkjonesjr

I've used the timetools NTP servers on many occasions and can't fault them, great for PLC and isolated SCADA systems, keeps all the date time stamping in synch
 
We have to set the PLC Clock in Rockwell PLCs as we use triggers at 7am on a Monday morning to reset counters for our Production Management System.

We use the free tool from Rockwell to run on our Transaction Manager servers to set the PLC clocks on a regular basis, to keep time with the server.

Logix5000 Clock Update Tool - comes on the DVD with Logix5000.
 
If you are using AB PLC, you can use PTP time server on the network. Contrologix will automatically sync to PTP server and AB Alarm and Event server is able to do ms level logging to OPC server (this last part I haven't dealt with).
 

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