LabVIEW

cancel
Showing results for 
Search instead for 
Did you mean: 

Help needed with Continuous PDF vi

Solved!
Go to solution

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.

0 Kudos
Message 1 of 7
(3,116 Views)

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.

Josh
Software is never really finished, it's just an acceptable level of broken
Message 2 of 7
(3,086 Views)

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. Smiley Happy

 

 

0 Kudos
Message 3 of 7
(3,084 Views)

@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. Smiley Happy

 

 


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?

Josh
Software is never really finished, it's just an acceptable level of broken
Message 4 of 7
(3,080 Views)

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! Smiley Happy Thank you.

 

 

0 Kudos
Message 5 of 7
(3,073 Views)
Solution
Accepted by topic author AT12

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.

Josh
Software is never really finished, it's just an acceptable level of broken
Message 6 of 7
(3,066 Views)

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. Smiley Happy

0 Kudos
Message 7 of 7
(3,061 Views)