divide Internal Sample Clock (VCXO)

[Jirav_Fadia]

Hello all,

I want to divide down internal sample clock source of my PXI 5122 High Speed Digitizer card.

Pxi 5122 has 200 MHz Internal Sample clcok source. I want to sample my data at 10 MHz.

So I want to divide down internal sample clock by 20 factor.

I want to do it programatically.

I didnt find any vi or property node for that (although found proprerty node for divisor input in NI Scope...but that was used only for reference clock not for onboard clock)

Help me as soon as possible...

[Henrik_Volkers]

Why not use the NIscope horizontal setup vi (or driver call ) and set the samplerate?

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@Jirav Fadia wrote:

Hello all,

 [...]

Help me as soon as possible...

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A hint I usually give my children ( sorry, I can't resist here) : The small word 'please'  will motivate much more persons to spend time for your problem.

[Jirav_Fadia]

Thanks for your reply... I will check it and get back to you.....

Sorry for not using please.... but now thanks a lot for showing interest on my problem and for using your precocious time....

[dansch · Accepted solution]

Hi Jirav,

I just wanted to clear up some things. The 5122 has a maximum real-time sampling rate of 100 MS/s (not 200 MHz as you originally suggested). To get a rate of 10 MHz, you would be dividing down by a factor of 10. From page 13 of the NI 5122 specifications document:

Just to add to what Henrik suggested, the following help topic describes the specific VI he mentioned for configuring the horizontal properties such as sample rate:

http://zone.ni.com/reference/en-XX/help/370592P-01/scopeviref/niscope_configure_horizontal_timing/

Most NI-SCOPE shipping examples use the above VI and there is an input for "min sample rate" where you can simply specify a value of "10M" or "10000000" to get the device to sample at the lower rate.

Note: Because the digitizer only allows sample rates that are an integer divide-down of the maximum sample rate, the rate will always be coerced up to the next highest legal sample rate. For example, if you specify "9.8435M", it would automatically coerce the rate up to 10 MHz. To see the actual value that the digitizer is using, you could query the "Actual Sample Rate" property node at any point in your code after the configurations have been committed to the digitizer. The help manual describes this property on the following page:

http://zone.ni.com/reference/en-XX/help/370592N-01/scopepropref/pniscope_actualsamplerate/

Regards,

[oscilentinc]

Great Input. I am thinking of useing one of these timing crystal filters http://www.oscilent.com/catalog/Category/vcxo.htm which one do you think would be the most applicable for me?