Multifunction DAQ

cancel
Showing results for 
Search instead for 
Did you mean: 

Resolution or step size of time of a digital pulse train from a counter output of PCI-6221

Hi Guys,
 
I am using PCI-6221 Card- Counter Output (32-bit).
Basically my requirement is to adjust the pulse train HIGH time and LOW time as fine as possible.
I want to use this pulse train for Frequency-Voltage converter where accuracy is NOT compromized.
 
please share your knowledge of how small the increments of HIGH and LOW times. and the accuracy of the pulse train generated.
is there any way i can test the pulse train?
0 Kudos
Message 1 of 4
(2,902 Views)

The 6229 has an 80 MHz internal clock available to drive the timing of your pulse high and low times.  Each must be an integer multiple of the timebase clock, so you get 12.5 nanosecond resolution.  The frequency resolution is variable -- very high freqs produce very coarse increments of frequency while very low freqs produce very fine increments.  This is inherent in the fact that freq comes from 1/integer.

Depending on the frequency you're generating, you may need to override some of DAQmx's default behaviors.  At lower output frequencies, it may decide to use a slower timebase unless you configure explicitly to use the 80 MHz one.

Note too that frequency and/or duty cycle can be changed on-the-fly without stopping the pulse train.

-Kevin P.

CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).
Message 2 of 4
(2,898 Views)
Mr. Kevin,
 
Thanks for making me understand the concepts of Time base and the frequency.
Is there any way to change the timebase (i remember it is thru some property node in LabVIEW).
If so, please tell me the various time bases that PCI-6221 supports.
0 Kudos
Message 3 of 4
(2,893 Views)
Is there any way to change the timebase (i remember it is thru some property node in LabVIEW).
If so, please tell me the various time bases that PCI-6221 supports.
I'm not at my LV pc and can't be 100% sure of syntax.  I *think* it can be found as a DAQmx Channel property node. 
 
The available timebases are 80 MHz, 20 MHz, and 100 kHz.  More specs and other useful docs can be found from the 6221 product page.
 
-Kevin P.
CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).
0 Kudos
Message 4 of 4
(2,890 Views)