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Synchronize the data aquisition with an external clock signal

Hello I am a student of Spain.


I wanted to synchronize the GPCTR 0_OUT of my PCI 6013 with the signal of a fuction generator.

For this synchronization I connect the reference clock of the generator (10MHz) to a PFI that I have configure ( I use Counter Set Attribute) like source of my GP Counter 0. I can observe that the signals are not totally synchronous and in addition the delay to the output signal of the counter with respect to the signal of the generator increases with duration of this signals.

I thought that this factor of delay is due to the length of the cable, but would this delay factor have to be constant ?.

In order to obtain a signal TTL of 50Hz with my counter 0 and a duration of 1 second there is a delay error approximated of 1ms with respect to the sine of the geneardor. If increase the duration in 2 second the delay is of 2ms.

I am using LabView 7,0 and NI DAQ 7.2 and my card is PCI 6013.


I wanted to know if this error in the synchronization is due to the cable and like solving it.


I sorry for my bad english. Thanks
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Miguel,

First, delays in the order of 1-2 msec will not be due to your cable length.

Second, it is not clear to me how you are trying to synchronize to the function generator. It sounds like you are using a 10 MHz reference clock as a source for your 50 Hz output from Counter 0, but I don't see what would synchronize it to your function generator.

The reason that the delay changes with duration is that you aren't generating the exact same frequency with the two devices. Perhaps your function generator isn't truly creating 50.000000000 Hz cycles. Or perhaps your 10 MHz reference clock isn't truly 10.0000000 MHz. Or (most likely) both.

To synchronize Counter 0 to the function generator, you should:
1) generate a TTL square wave with the function generator and use it as a source signal for your Counter 0.
2) ideally generate a square wave with the function generator that is even integer multiple of 50 Hz, such as 200, 300, 400, etc.
3) configure your Counter 0 pulse train units to be "Ticks". If the function generator is at 200 Hz, you'd configure for 2 low ticks and 2 high ticks.

-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).
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Hello Miguel,

what you are trying to do is completely possible if you follow the instructions from Kevin.

Where you able to get this working?

If not, please post a simple example and we'll take a look at it (please include info on the external connections you are making to test the example).

Regards,

Jorge M.
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