Getting high data acquisition rate (Under 1ms)

Hello,
I'm having a bit of trouble with data resolution when taking voltage measurements from my photodiode. I have been collecting data at about 1 point per ms and I need to be collecting at a resolution greater than this (however my actual needed resolution is not yet known as the signal is currently buried due to resolution problems). I'm currently using labview version 8.6 to collect data from a ThorLabs PDA36A amplified photodetector (resolution of 17MHz) running to a NI BNC-2110 and then to a PCI-6143 card with a 250kHz resolution. I've attached the code below.
The one item of interest that I have noted is that I am able to select the frequency of data collection in the DAQmx_read.vi properties however whenever I run the code all it spits out is one point per ms. With any frequency higher than 1kHz (which is the default) the data output occasionally puts 5-6 data points at one time each time being on ms apart.
Any help will be appreciated.
P.S. I've attached both files which I use to check our data. The Light Sensor is the file that collects the data, the Read File file just spits out a graph after I've saved the information. I've tried to speed this code up as much as possible and am now convinced code speed is no longer an issue and that the problem lies elsewhere.
Message Edited by Luminescence9 on 05-19-2010 02:44 PM
Attachments:
Light Sensor.vi ‏17 KB
Read File.vi ‏51 KB

On your DAQmx Timing vi, you need to specify the source input to Onboard Clock. Otherwise you have no timing source. On your DAQmx Read vi, set the polymorphic selector to Single Channel - Multiple Samples - Waveform. Then use the Get Waveform Components to get dt. This gives the time interval between samples. You can use the same Get Waveform Components to get Y, which is the same 1D array of data as you get in your original code.
If you use the Waveform data type, you can wire it directly to a Waveform Graph and eliminate the top loop altogether.
- tbob
Inventor of the WORM Global

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Message Edited by Marc A on 01-16-2006 05:07 PM
Message Edited by Marc A on 01-16-2006 05:09 PM

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