Best OPC reading method

[bartb]

Hello,

I am working with a WinCC OPC server i would like to read out the tags in Labview 8.5. This works fine, but i get some errors when my logging of the wincc opc tags is to fast . Whats the best way to read out as fast as possible and without errors about 50 tags? Some example code?

at the moment i use the open read and close commands in a loop for 50 iterations with different opc addresses. Maybe i can do the reading parallel instead of serial.

Thanks in adavnce,

B Bakels

[yenknip]

I have a few dozen opc addresses to open and read/write. What I have done is to use an action engine to open the addresses, then store them all in a cluster an unitalised shift register. I call a 'use' action which reads the cluster, and a destroy case which closes all the references. In doing this I am saving computation as I do not need to open and close references every iteration. I can post a pic if you like?

Can you just confirm that I read your post correctly - The server is faster than you can read from it, so you need faster a reading algorithm?

[bartb]

hello thanks for your reply, yes a picture will be great. Im not sure if my server is fast enough but i sometimes i get a undefined error.

Thanks

B Bakels

[yenknip]

I think these VIs should demonstrate what I mean. Essintially whay what I have done is to take the open and close outside the main reading loop. This will massively speed up the reading, as you are not opening / closing a lot of references every iteration.

A thought I've just had, is that the undefined error may be if you are trying to write to a read-only process variable? I've done this a couple of times 😛


Message Edited by yenknip on 06-19-2008 12:01 PM

[yenknip]

Another thought - You say the error does not always happen, have you got the 'wait for updated value' set to false? It may cuse a timeout error if left to true.





Message Edited by yenknip on 06-19-2008 01:12 PM

[bartb]

Nope, that wasnt the problem but thanks for the solution. You way of opening the opc items was much faster the creating the ref each time i want to read out al items.

Thnx,

B Bakels