Spurious readings on FP-1600 using OPC server

[Puho]

We have implemented 4 frequency meters using a FP-CTR-500. We are monitoring one input status (linked to an internal counter generating 1 Hz pulse) through a VB application with OPC server, on Windows NT 4.0 (the same using Win 98). Sometimes, the readings (one per second) look as "freezed" but the counter module is going OK (we are sure about that). Is there any special seting of module to avoid those false readings?

[Green_Rives]

There are no special settings on the module to avoid the false readings that you are talking about. It sounds like there is nothing wrong with the counter module, but with the program on your computer.

Are you reading the values from the OPC server? If you are using datasockets, you cannot use the ReadAutoUpdate access mode with OPC servers. It will give results similiar to what you are talking about.

[Puho]

Dear Green,
We don't use datasockets and ReadAutoUpdate access mode. We are using timers from VBasic and one standard dll (from Siemens in this case) to communicate with OPC Server. Has National its own dll to interface the OPC Server. Where do you recommend find the problem? Best Regards,

Eduardo

[Green_Rives]

National Instruments does have a dll that you should use to talk with our OPC servers. It is called opcdaauto.dll You can find it by searching for:

visual basic opc dll

on our main website, www.ni.com.

The first result is "Controlling OPC Servers with the OPC Automation API in Visual Basic - Example..." This example has a copy of the dll that you should use to access our OPC servers.

[Puho]

Dear Green,
We have installed the opcdaauto.dll from National and there was not change in the trouble of "data freezed". We think the problem is the time management in VB application. We are thinking in replace the sub module currently used to generate interrups at fixed time, by other new more secure version writen in "C" language.
Best Regards,

Eduardo

[Green_Rives]

Eduardo,

That may be the cause. Please let me know if this solves the problem.

[Puho]

Dear Green,

The sub-routine writen in "C" language is a pending project yet...By other way, we have modify the current method of VB timer management in our application, and we have obtained an important reduction in events of data lost (or freezed). Thank you very much for your answer. Best Regards,

Eduardo