I have sampling rate issue on extracting data from 1D Array of Cluster of 2 Elements.

[Abebae]

Hi. I am using Micron Optics sm130 for intensity measurement by tweaking original driver.

Original data from sm130 (optical sensing interrogator) is 1D Array of Cluster of 2 Elements (sampling rate: 1 kHz). 

I unbundled the data using 'for' loop and extract spectrum data of single wavelength which I am interested in.

Below is the schematic of my vi code. 

 

I got data from the vi but sampling rate was much lower than I expected. I got only 10 Hz data.

Can anybody can give me some advice if there is any problem in my code.

Thank you in advance. 

[RavensFan]

1.  Are you sure you are getting 1 kHz worth of data out of the subVI?

2.  Do you know how long the Extract portion of signal is taking to run?  Or how long of a portion it is extracting?

3.  Do you know how long it is taking to write the data out to the measurement file?

[Dennis_Knutson]

Well, I'm confused about the whole mention of sample rate. I don't see anything related to sample rate except how often you query the instrument. The only dt being passed to both Express VIs is 1 because the Convert to Dynamic Data is going to use a default dt of 1. You have not provided any mechanism to use anything different.

[Abebae]

Thank you so much for your advice and comments.

I tried to verify how long the Extrac portion of signal and Write the data out to the measurement file.

I generated 1 kHz signal using Simulate signal and got 1 kHz signal using Extract portion of signal and Write the data to the file.

As you guys said I need to verify if I am getting 1 kHz signal from the subVI for each wavelength.

Thank you again and have a good day. 

[Dennis_Knutson]

Again, mention of sample rate is meaningless. You still have not posted the code so no one knows how you have programmed the Extract Portion of Signal and there will be no relationship to actual timing and what is the reported timing in the file you create. Look at what you are doing. You have a 2D integer array. Where do you see any timing information in that array? All that you can process and record is number of samples.

[Kristen_K.]

Hi Abebae,

You said you were trying to extract a particular wavelength, which it looks like you are doing successfully with the Extract Portion of Signal Express VI- yes?  Since optical data comes back as a spectrum of wavelengths, it is handled a bit differently than typical DAQ signals. 

Where in the code and how are you verifying the sample rate?  In other words, how did you come to the conclusion of getting only 10 Hz data?  Also, out of curiousity, why are you needing the sample rate?

I have some experience with optical DAQ devices, so I'll do my best to answer your questions. I look forward to your reply.

[Abebae]

Thank you so much for your help Dennis and Kristen. As Dennis mentioned there is no dt signal in my data set. Actually I couldn't figure out how to get that dt information from sub VI. I began learning Labview by myself from last month and am still learning how to use it. So my questions might not be well refined.

My goal of the present experiment is to measure dynamic response of optical sensor which I made. In my experiment I am trying to evaluate how fast the sensor reacts with respect to sudden pressure change (dt <1 ms). Conventional electric pressure sensor is used as reference. I hooked up optical pressure sensor to sm130 (sweep laser light source (wavelength bandwidth: 1510nm ~ 1590nm) + spectrometer) and got spectrum (intensity) data of one wavelength using extract part of signal using the code attached. Actually I have one more data set from electrical pressure sensor (Kulite sensor). It's sampling rate was set to 1 kHz. I estimated sampling rate of optical signal by comparing the number of data from optical sensor with electrical sensor which is 1 kHz.

I attached zip file of my VIs. If you are available, please take a look at it and give me some advice. File name of the VI I am using is "Micron Optics sm130 Acquire Continuous Spectrum_Modified_Ver1" in the directory of "SM130". Thank you again, Dennis and Kristen.

[Kristen_K.]

Hi Abebae,

I have the driver for the sm130 installed but don't have a sm130 so can't run any tests.  I'm wondering if the  Read Data Spectrum VI would actually be more useful for getting timing data since there is a timestamp output.  

Do you have multiple sensors on one fiber (aka one channel)? 

Message Edited by Kristen H. on 03-19-2010 01:17 PM

[Abebae]

I tried to use that but I couldn't. When I add while loop in that code, it give me error message.

It looks like sm130 cannot handle that. When I applied while loop to any VI in the same folder with Read  Data Spectrum,

it gives me the same message. That's why I couldn't use that.

And I have only one sensor in one channel. Thank you so much for your help. 

[Kristen_K.]

What was the error? maybe there's something else going on....