DAQ write DAQ read synchronisation

Hi,
I want to create the Low Pass Filter Tester with TestStand. I want to generate sine wave with frequency form 1 to 1k Hz and read amplitude before and after the filter. First of all I have to ensure synchronisation between DAQ read and DAQ write[ http://i79.photobucket.com/albums/j122/thor_tory/1_zpsab4a4c00.png~original ]. I already used a bit modified examplary sine wave generator to analog output VI and read from analog input VI. I put them as subVIs into one VI and then called it in TestStand although the read apmlitude was in many cases not even close to the generated amplitude (like the read was performed too soon). I put all subvis one by one, I also tried flat sequence structure but it was not ok because it stopped in first stage while generating sine wave.
Have you any idea how to make synchronisation between generating signal and acquiring amplitude? And what to match it to given frequency (value of frequency is increased in TestStand)?
Michał
Solved!
Go to Solution.

Thanks for showing me that example, I have somehow problems finding it myself What is the difference in using that built in clock?like in this example:https://decibel.ni.com/content/docs/DOC-26326
Having set the acquisition finite I get an error:
Possible reason(s):
Attempted to read a sample beyond the final sample acquired. The acquisition has stopped, therefore the sample specified by the combination of position and offset will never be available.
Specify a position and offset which selects a sample up to, but not beyond, the final sample acquired. The final sample acquired can be determined by querying the total samples acquired after an acquisition has stopped.
Attempted to Read Sample: 50
Property: RelativeTo
Corresponding Value: Current Read Position
Property: Offset
Corresponding Value: 0
Task Name: _unnamedTask<4F>
I've been changing all the values but I keep on getting that error. Is there any way to make everything dependent on the frequency of generated signal(I know it is )? I mean like sine wave f = 100Hz
so the f_sampling = f * 2.5 (to prevent aliasing), same thing with samples to read, does the amount of them have to be the same for every channel?
Michał

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DIO_write_read DAQ from file.vi ‏17 KB

What does your file look like? The DAQmx write is expecting a single U32 value, not an array of I64.
Message Edited by vt92 on 09-16-2009 02:42 PM
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Solved!
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StepanieO,
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