LabVIEW

cancel
Showing results for 
Search instead for 
Did you mean: 

Clock drift on a cRIO ... getting way more points than expected?

Solved!
Go to solution

I discovered an odd issue today.  I have a really simple LV RT application that is running on a cRIO 9040.  It captures AI voltages at 20kHz. 

 

I noticed that I was getting a lot more samples than I expected.  It seems like either the clock on my CRIO or my system clock is really inaccurate.  Or I am just doing something wrong.  

 

I suspect it is the cRIO because when I sample some OPC tags, they match the count on my Windows clock.  

 

Below is a screenshot of my code.  And I attached my code, too.

 

Can someone explain this to me?  I should be getting 20,000 points a second, but it looks like I am getting a bit more than that?

clock drift example.png

 

http://www.medicollector.com
0 Kudos
Message 1 of 6
(132 Views)

Hi j,

 

Which DAQ module do you use?

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
0 Kudos
Message 2 of 6
(107 Views)

It’s a NI 9232. Going to use it for some remote vibration measurements. 

http://www.medicollector.com
0 Kudos
Message 3 of 6
(82 Views)
Solution
Accepted by topic author josborne

The 9232 is a DSA device. It can only sample at specific divisors of its internal master time base, 13.1072 MHz.

 

I am guessing that it is sampling at 20.48kSa/s. The formula is

mcduff_0-1741997667669.png

 

Message 4 of 6
(76 Views)

Oh wow that is totally it!  Thank you!  

http://www.medicollector.com
0 Kudos
Message 5 of 6
(64 Views)

Hi j,

 


@josborne wrote:

Oh wow that is totally it!


Yes, reading the specs/datasheet often helps... 🙂

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
0 Kudos
Message 6 of 6
(33 Views)