data acquisition

[Philip]

I am measuring the voltage from a photodoide. The light intensity falling
on the diode is changing very quickly. The signal from the diode is fed
to a lock-in ampplifier and then to a Bytronics card.

My labview programis not responding fast enough to the rapidly changing light
intensity falling on the photodiode. The program consists of a sequence
structure. In the first sequence it waits a period of time. In the next
sequence a measurement is taken and wrote to a spreadsheet. The sequence
is placed in a for loop. The program is unable to respond to fast light
intensity changes.

Also can buffering be used in the program, if the card used is a Bytronics
card.

Thanks

Philip

[markwysong@my-deja.com]

In article <3933fb48@newsgroups.ni.com>,
"Philip" wrote:
>
> I am measuring the voltage from a photodoide. The light intensity falling
> on the diode is changing very quickly. The signal from the diode is fed
> to a lock-in ampplifier and then to a Bytronics card.
>
> My labview programis not responding fast enough to the rapidly changing light
> intensity falling on the photodiode. The program consists of a sequence
> structure. In the first sequence it waits a period of time. In the next
> sequence a measurement is taken and wrote to a spreadsheet. The sequence
> is placed in a for loop. The program is unable to respond to fast light
> intensity changes.
>
> Also can buffering be used in the program, if the card used is
a Bytronics
> card.
>
> Thanks
>
> Philip
>
Philip,

First, I don't know if a Bytronics card buffers data into memory. That would
be something you'd have to look up in a Bytronics manual.

However, there are ways to speed up even a single point acquisition: 1) Use
the DAQ->Analog Input->Utils->AI 1 Scan VI and initialize the acquisition on
the first pass, and then just read the card on the next pass. (Or you can do
this with your own VIs that control the Bytronics) 2) Save the data into an
array, and write the data array at the end. Opening and closing files takes
a lot of time. If that's not possible, write 100 samples at a time. 3)
Decrease the amount of wait time in your sequence.

Mark


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