Watching quick events onscreen


Thread Starter

Dale McLaughlin

Short duration events in our Quantum plc are not shown in Proworx nxt online display. It seems more likely a computer problam than a Proworx one. What would be a solution? Faster computer? Faster monitor refresh?

You can catch the event using the "trend" function. Another way latch it with a "dummy" coil then unlatch with a timer function!!
I caught the contact turning on the coil using an upcounter, It would not show up when trending. I can see the output light turn on on the card in the rack but it would be nice to see it onscreen.
> Short duration events in our Quantum plc are not shown in Proworx nxt
> online display. It seems more likely a computer problam than a Proworx
> one. What would be a solution? Faster computer? Faster monitor refresh?

Proworx NxT is as slow as molasses when communicating through an RS-232 link. The problem seems to be the way the NxT comm driver
is written. To me, it looks like it does screen updates and Modbus comms one at a time, rather than in parallel. Getting a faster computer will help some, but not much. Monitor refresh is not the problem. Using ethernet will help a lot. If that's not fast enough I think you'll need some other tool.

Jay Kirsch

Joseph Luft, FasTrak SoftWorks, Inc.


Depends on what you define as short duration. The ProWorx NXT product is notorious for slow screen and data update rates. A faster computer may help a bit. If you are using a serial connection, you could move to a faster communication like TCP/IP.

The best solution may be to move to a full 32 bit software product which uses an high speed OPC server for communications.

Good Luck. Joe

Joseph Luft
FasTrak SoftWorks, Inc.
6659 W Mill Road
Milwaukee WI 53218

1-414-358-8088[email protected]
It is not likely a computer problem, and monitor refresh rates have nothing to do with it. When Online to the processor with ProWorx, click on the 'Edit' menu and you will see an option for 'Update Rate'. This controls how fast the ProWorx will poll the PLC. If this is already set as fast as possible, then there's not much you can do other than put in a latch circuit to hold the coil on until reset by a command or timer.

It also depends on the size of the program, the number of coils & registers used, and the range of addresses used as well as the communication method. Ethernet and MB+ will be much faster than serial.

One note regarding the update rate: The online documentation suggests that the absolute best case for update rate is approximately 55ms, due to overhead, etc. More likely you will see in the range of 200-500 ms, which could be as many as 10-50 scans. Also be aware that if you set the update rate very high, all other applications and even mouse and keyboard commands will become very sluggish.

Hope this helps.

Don Zunti, P. Eng.
Delco Automation Canada
Saskatoon, Saskatchewan
Or Modbus Plus. All Quantum PLCs have Modbus Plus ports. The modbus Plus protocol is 1MB/sec, so it's worlds faster than RS232. You can get a Modbus Plus card for your computer and communicate that way. Or you can buy a Modbus Plus to Ethernet bridge and allow any machine with an ethernet connection to share the Modbus Plus card. I personally recommend the bridge
solution, that's what we use in our classroom. The cards are expensive, but the bridge is just a bit more and allows everyone to use it. Alot cheaper than several cards. Proworx NxT will communicate over ethernet through the bridge.

I can give part numbers if required.


Curt Wuollet

That's fairly simple. Modify the software to update on the event you want to see. Oh that's right, never mind, you don't have source for your tools.


Even if i had the source code, I doubt highly my background would help me to reprogram the Proworx NXT package. I have seen in other vendors' software an indicator that you could display on the screen that would count the transitions and displayed a colored box that changed colors when the selected condition was met. It even had the option to sound an audible beep in the PC speaker when this occured. I'm sure some of you know which software I'm referring to... Would be nice of NXT or even Concept had this option.

You are trying to observe a short duration event from another computer with the graphical interface of the programming software(regardless of manufacturer) which is not the best method because it is dependant upon communications, PC CPU speeds, programming software design, drivers, housekeeping functions in the PC, etc. etc. etc.

As other posts have mentioned put in a latch to catch it. In other words, let the PLC program do the monitoring for you. In all of my years of programming and troubleshooting that is the most reliable method if you absolutely must know the event occurred.
[email protected]

My point was, if you were using Open Software, it'd not only be nice, but feasible to add it. Before long, the feature set would be awesome. If we all put in a little...........
Of course, you _could_ ask the vendor to add it for you :^).
We ought to have the LPLC ready by then.
I'll add watchpoints to the list.