Real time acquisition's time quantification

[Real Time Acquisition]

I am performing a real time acquisition with a PCI GPIB for digital data. I acquire data continiously for say 60 minutes. Now I want the clarification how exactly is this time (ie 60 minutes) exactly equal to 60 minutes? or is there any deviation? if so how is it quantified.

So, As i am using PC as time source-  This needs to be quantified or verified for time how is this done?

Vishwanath

[Daniel_E]

Hey, 0.015625 seconds is the limitation of the time stamp.  If you are using a Real-Time control with the Real-Time operating system, then this is the true limitation.  If you are using Windows, then it may be this and it may not.  It is totally dependant on what Windows is doing and is out of LabVIEWs control.

Hope this helps!

Dan

[Real Time Acquisition]

Hi Daniel Thanks for your interest!

See i am using the vi for calibration of a cesium frequency standard by comparision method which is having  an accuracy of 1x10e-11 ppm. So here the stability is measured by the time taken for change in phase. Here though i have used time stamp, i feel that as I am making measurements from a particular time to time the time has been referenced. hence the time taken will have CPU time and our time stamp will be intre[reting in reading the time from it.

So, in this case

1. how good is the cpu/ mother board time ?

2. How shall that crystal in Mother board characterised?

I hope my interpretation is right.

with regards

Vishwanath

[Daniel_E]

Hey, I am a bit confused.  Are you talking about a specific real-time controller?  If so, which one. 

[Real Time Acquisition]

Hi Daniel, It's no specific I have used the time stamp as a part of my program to build a VI for capturing time vs voltage signals.

[Daniel_E]

Gotcha, then what I said before stands.  The time stamp in LabVIEW is a data type.  That data type is limited to 0.015625 seconds of accuracy.  That is just a limitation of the data type.  Let me know if this helps.

Thanks!

Dan

[Real Time Acquisition]

Hey Daniel, You are specific to labview but I am trying to see the roots. As I have explained to you probably I should debug on mother board oscillator section for its stability/accuracy specifications.

If you can throw some light something on this i will be greatfull.

vishwanath

[Daniel_E]

So are you trying to do this on a windows computer?  If so, contact the manufacture.  If you are doing this on a Real-Time controller, let me know and I can get specs for you.

Thanks!

Dan

[Real Time Acquisition]

Thank you Dan!

Vishwanath