time taken for CVI under OS Win2000 to read DAQ devices in ISA slots

[owlowl]

Hi,

I am acquiring some analog signals from an ISA DAQ card. I have used the low level driver in labWindows/CVI to enable me to read data from this DAQ card under Win2000 OS.

However, as Win2000 is not a real time OS, i wonder if there is any way i can check what is the delay incurred... I know the sampling speed of my DAQ card.

Hope someone has some answer to this... Thank you.

Wee

[BeckyB]

Hello Wee -

What delay do you want to check? Can you be more specific about the delay?

There is no delay between the data being digitized and put into the driver memory (it is neglible).

If you are wondering about the delay between data entering the driver buffer and being read by your program, there is no direct way to calculate this. It varies based on when the Microsoft operating system allows memory access.

However, if you are looking to measure the delay between samples, please review this KnowledgeBase or your user manual.

Please let me know if these suggestions do not answer your question and I will continue to look into it. Have a great d
ay!

Becky B.
Applications Engineer
National Instruments

[owlowl]

Hi Becky,

Thank you for your response and answer.

Actually i think i am trying to measure the delay between the data entering the driver buffer to being read by my program. Correct me if i am wrong. The situation is like this.

I have a DAQ program running in CVI under Win2000 using your ... I want to compare the speed of this signal acquisition with one which i use exactly the same hardware but now i placed the acquisition program running on a real time OS like running RTX in parallel with Win2000 but still using my original CVI interface. The CVI will now access the DAQ card through the RTX instead of using the

Thank you

Wee

[BeckyB]

Hi Wee -

The simplest answer is that if you want a deterministic process, use RTX. Windows 2000 is nondeterministic and system dependent.

The only way you can attempt to measure this is by using an external program, but adding in any functions to measure time will result in an inaccurate reading.

I hope that helps! Have a great day!

Becky B.
Applications Engineer
National Instruments

[owlowl]

Thank you... well guess i can try out some stuff to get what i want

cheers

Wee