08-10-2012 05:06 AM
Hello,
I have a DAQ Assistant that supplies Voltage-Time data. I now want to create a PDF(Voltage) vs Voltage distribution plot, as shown in Fig 1.1 in the below link:
http://www.analogzone.com/avt_0904.pdf
I've built the Continuous PDF vi into my project but it isn't giving me the result I wanted. I wonder if it is taking time as pdf(x) instead of voltage?
Attached is my project.
I would be very grateful for some assistance with this. Thanks for your attention.
Solved! Go to Solution.
08-10-2012 12:11 PM
The "Continuous PDF VI" you are using gives you the Y value of an existing pdf function. Not calculating the pdf of a set of data.
The figure that you pointed out is actually just a histogram rotated 90deg. Get rid of the for loop and input the double array directly into the histogram vi and create an indicator from the output.
08-10-2012 12:19 PM
1) OK, but how do I get the histogram as a curve, not as bins?
2) What would be the pest way to calculate the PDF of the data?
Many thanks for the reply.
08-10-2012 12:33 PM
@AT12 wrote:
1) OK, but how do I get the histogram as a curve, not as bins?
2) What would be the pest way to calculate the PDF of the data?
Many thanks for the reply.
1) Go into the histogram properties and tweak with the plot tab. Fill to none and changing the lines will help. You can also decrease the step size.
2) I'll answer with more questions. Do you need the pdf equation or just a graph? Do you need it of the entire signal, or just the noise?
08-10-2012 01:41 PM
Thanks for that, I tried the histogram earlier and it worked fine and will look better with your suggestion.
In answer to your questions:
Q1) I need a graph on the front panel, with the data to be saved through the 'write to measurement file' with all the other data.Q
Q2) This is all for noise measurement.
This is much appreciated by the way - this is a great forum to learn from and reduces a lot of stress! Thank you.
08-10-2012 03:27 PM
Ok, then the histogram will work for your needs. It's "effectively" the same as a pdf (a statistician can detail the finer points, not me). Plus it's easier.
This approach, at the moment, does not measure just the noise. It's the entire signal. I'm not sure where to begin because methods for subtracting the signal to get the noise depends on your signal type. You may need to experiment.
08-10-2012 03:42 PM
OK thanks. If I were to want the pdf of the singal how would I got about it?
What function would I use to subtract the signal?
The voltage signal comes from a low noise current pre-amplifier by the way and then through a DAQ board.
Thanks again.