Testing RC Circuit

[Jeff Dillon]

We have a graduate school homework assignment where we need to generate a AC
waveout (DACOUT), then measure the response and phase shift (if any) of an
RC circuit (DACIN)

Since this is a homework assignment, I'm just looking for general advice. I
am using a NI 6024E Card.

I am able to generate the output waveform OK. But then I need to measure the
rc waveforms on either side of the RC circuit. How can I measure phase
shift, since both signals would need to have a common time reference?

I tried just generating a single cycle waveform, and tried capturing the
result using triggered acquistion. But my board doesn't support hardware
analog triggering, only software triggers.

Any suggestions?

thx

Jeff

[Doug (CapeFl)]

The trick to your task is to add the same reference number (trigger) to each waveform cycle [synchronization of data]!
Could you build a multi-dimension array (1 dimension for each RC circuit) using a For loop, where the iteration number of each For loop represents the waveform cycle number (array index) for the readings of each cycle? Thus, each For loop will increment only after all measuremetns have been indexed into your array.
After recording the data, you compare each deminsions based on the triggered index number.
Just a thought - Good Luck.

[Steve_M.]

Hi Jeff,

What you basically need to do here is simultaneous analog input/output. I would recommend doing this by having the analog input and output share the same clock. This can be done by using the route signal vi to connect the analog input scan clock and the analog output update clock through either PFI5 or PFI7 depending on which clock you want to use as the master. This is outlined in the link below:


http://zone.ni.com/devzone/explprog.nsf/ webmain/ 913E26CCF1019BBB862566EB007BB202?opendoc ument


After you have the simultaneous analog I/O portion of your code running, you should be able to use the cross power spectrum vi to input your two time domain signals and take a look at the phase difference between them. Good luck.

-Steve

[Tomoya ITO]

Hi Jeff,

Simultaneous triggering on a couple of boards has difficulties
in some points, but is it sure that you just want to do on two
boards(input and output voltage)?

If so, it is better to have time wait unit involved in a
processing loop for synchronizing two wave forms aquiring.
A simple loop process generally consumes about 10-20ms per
one loop without multithread function, so time wait is to
be set at least 10ms. Please try to set it gradually up
to appropriate value.

Of course whether my suggestion is valid or not is quite
depending on frequency of your RC circuit. Hope it helps.

Thanks,
Tom (Tomoya ITO)

Jeff Dillon wrote:

> We have a graduate school homework assignment where we need to generate a AC
> waveout (DACOUT), then measure the response and pha
se shift (if any) of an
> RC circuit (DACIN)
>
> Since this is a homework assignment, I'm just looking for general advice. I
> am using a NI 6024E Card.
>
> I am able to generate the output waveform OK. But then I need to measure the
> rc waveforms on either side of the RC circuit. How can I measure phase
> shift, since both signals would need to have a common time reference?
>
> I tried just generating a single cycle waveform, and tried capturing the
> result using triggered acquistion. But my board doesn't support hardware
> analog triggering, only software triggers.
>
> Any suggestions?
>
> thx
>
> Jeff