When you configure a hardware analog trigger in ComponentWorks AI control, you
are configuring a one-shot acquisition. The trigger (start or stop) should go
high when the trigger conditions are met. The AcquiredData event will be fired
when the correct number of scans have been acquired. The acquisition then
stops. You will have to restart the acquisition to take another measurement and
see another trigger signal on the ATCOut circuitry. Depending upon the
frequency of the analog input signal, you may miss triggers because the
acquisition was not been restarted in time. To measure frequency in the way you
described would require a continuous acquisition that exerts a hardware signal
each time the conditions are met. This functionality is not currently available
in ComponentWorks.
To treat the signal as an analog signal and measure frequency, I would recommend
using a software algorigthm such as AutoPowerSpectrum and PowerFrequencyEstimate
(methods on CWDSP control) to determine the frequency of a large sample of data.
To perform a hardware measurement of the signal, I believe that you could build
an RC circuit that would transform the analog input sine wave to a TTL signal.
You could then configure a counter for a frequency measurement based on the
incoming signal.
"paulkelleyisme@my-deja.com"
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Subject: Re: Frequency Measure Sample
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natinst.public.componentworks.general
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Hi,
I work for GE in a test development department. We are using NI DAQ
boards in an ATE we are building for testing circuit boards in for
repair.
I am trying to read frequency on the VXI MIO 64E-1 analog input board.
I want to choose through software any of the analog input channels to
read frequency on. I am trying to route the analog hardware trigger to
the general purpose counter to do this as well as using the on board
timebase. I figure one cycle of the analog input signal will enable
the counter and I will count the timebase pulses. From that I can
figure the frequency. I am using the counter and analog in component
works(version 2 full development system) controls in visual basic. It
doesn't seem to be working. I'm not sure I am routing my signals
properly.
Am I right in using the AI control to configure the hardware trigger?
Will the hardware trigger only work while I am doing a AI read on the
desired channel? (I don't care about the actual voltage read on the AI
channel, just the frequency)
Any suggestions?
Also, is there better documentation than comes with the VXI boards or
component works. I am looking for logic schematics showing this
routing between the different areas talked about above. All I have is
very general block diagrams in the VXI catalog manual and the component
works manual only has timing diagrams on seperate sections. I find
myself trying to read the different sections and put it together by
drawing my own logic gates. I don't know if I am putting it together
right however.
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