Spectral Measurements - Y axis units?

All;
When I choose to use the RMS magnitude selection on the spectral measurements dialog attached below.... If I am taking angular velocity measurements in degrees/second, what are the units of magnitude on the y axis of the subsequent frequency domain result? Additionally, what are the units if I select any of the other selections? Thanks!!
-Nick-
Attachments:
Capture.JPG ‏66 KB

When the selection is rms the output units are the same as the input units. Power Spectrum units are the square of the input units and power spectral density is in units of (input units)^2/Hz. This information is in the detailed help for the VI.
Lynn

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Number of Points used in FFT calcuations using Spectral Measurements

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Hi,
The answer lies in the labVIEW Help file< If you dig deep enough through the hierarchy of the Spectral Measurment Express VI's, you will end up eventually to the Power Spectrum.vi or Real FFT.vi that can be found in the Analyze>>Signal Processing>>Frequency Domain Palette (see screenshot attached)>
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I will let you go through those files for details, but basically, when the number of samples in the input signal is a valid power of 2, the VIs compute the fast Fourier transform using the a fast radix-2 FFT algorithm.
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But the help file explains it better than me
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Attachments:
ScreenShot008.gif ‏29 KB

How do I count digital pulses and convert them to an x-axis unit?

I am a grad student in Chemistry and I have undertaken a project to switch an old spectroscopic instrument from a stepper motor chart recorder to a digital interface.
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I just measured the signals coming from the instrument, so I know exactly what I am working with.
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Hints:
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Making octave plot in SVT to use g/SQRT(Hz) units

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Session Facade and Access to a Non SQL Based Persistent Data Store

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E. Sulzer
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Plot xy graph

Hi I am just making a simple simulation model in which a result of a formula is the acceleration. This result I plot it against time. By integrating the acceleration I obtain velocity and by integrating the velocity I obtain distance. Those last results i plot them against time. However, when I tried to plot distance vs. velocity, it looks like a get a graph of distance against time. What would be the correct functions to be used to plot this correctly thanks. The first picture attached shows a view of part of the model and the second pictures shows the results of the graph that I getting. The graph that I need is taking correctly the y axis units but the x units are incorrect, it seems like it is just plotting against time.
Thank you
Solved!
Go to Solution.
Attachments:
plot xy graph.JPG ‏24 KB
graphs.JPG ‏34 KB

Hi,
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Regards,
Nitzz
(Give Kudos to good Answers and Mark it as a Solution if your problem is Solved)
Attachments:
Untitled 3.vi ‏12 KB

Draw rectangle in plot

How can i draw rectangle in graph
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Is there a way to make table entries vertical rather than horizontal?

I am wanting to make custom x-axis values which are names of sensors rather than numbers so i was going to just place a table to make the custom values. But i do not think Labview will allow vertical text like it is in the y-axis units. It only allows this for captions and labels. Does anyone know?

Here is a quick demo that is a bit more robust and picks-up on CC's suggestion.
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Message Edited by Ben on 09-17-2006 10:48 AM
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction
Attachments:
Markers.vi ‏27 KB
Text Mrakers.JPG ‏144 KB

Grphics Problem

Hi
I am working on Graphics 2.5. I am facing a problem while plotting XY Line graph. On X-Axis I am taking a Date column value, item description as sub-category and on Y-Axis Unit Price of the item is being shown, the problem is that the line/graph starts some where after the Y-Axis. which is not touching the Y-Axis at all. or rather I want to start the X-Axes values rigth from the axis starting point. (which if ORGIN of the XY Graph). On X-Axis, entire One unit is being considered as the value not exactly one perticular point.
Hope I made clear my requirement.
Badly I need the solution for this.
thanks
Mahesh
null

Hi, Beverley.
Thank you for visiting Apple Support Communities.
I understand that you are unable to trim clips using iMovie. I would need a little more information on how you were attempting to trim a clip to provide a better answer. However, make sure you have the movie project open and are selecting the clip that you wish to trim as this will activate the clip trimmer.
Trim clips
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How does Pulse Params Vi determine pulse width

I need to know how the PulseParams vi calculate pulse width, rise/fall time? Is it based on the standard 10/90 method or something else? How does it determine what is a "valid" pulse? What is the "Delay" parameter and how do you use it?

Hello Lancer,
The following is taken from LabVIEW Help under Pulse Parameters:
X is the input sequence. X must meet the following conditions:
� The number of samples in X must be greater than or equal to 3.
� X should have a rising edge, a plateau, and a falling edge.
� The expected peak noise amplitude must be less than 50% of the expected amplitude.
If the number of samples in X is less than 3, the VI sets all the pulse parameters to NaN and returns an error. If X does not contain a rising edge, plateau, and falling edge, the VI analyzes the data, assigns values to as many pulse parameters as it can identify, and sets parameters it cannot identify to NaN. The VI does not report this condition as an error.
Note X can be a positive- or negative-going pulse. A histogram is used to determine top and base. If the difference between top and base is negative, the pulse is considered negative-going with a negative amplitude.
If the data in X is noisy beyond the expected 50% amplitude, the VI does not have enough information to differentiate between glitches and pulse data and may assign incorrect values to the pulse parameters. Because it cannot be detected, the VI does not report this condition as an error.
Note If the data is noisy, you can apply a median filter to the data before passing it to the Pulse Parameters VI. Refer to Noisy Pulse Analyzed with a Median Filter for more information about analysis with a median filter.
Note When the X data is a constant value c, the VI sets the pulse parameters to the following values.
amplitude = overshoot = undershoot = delay = duration = 0.
top = base = c.
risetime = falltime = slew rate = NaN.
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overshoot is the difference between the maximum value in the pulse and the topline.
risetime is the time required to rise from 10% amplitude to 90% amplitude on the rising edge of the pulse.
top is the line that best represents the values when the pulse is active, high, or on. For a negative-going pulse, top is less than base and results in a negative amplitude. For a positive-going pulse, top is larger than base and results in a positive amplitude.
amplitude is the difference between top and base.
base is the line that best represents the values when the pulse is inactive, low, or off and is the level closest to zero. For a negative-going pulse, base is larger than top and results in a negative amplitude. For a positive-going pulse, base is less than top and results in a positive amplitude.
undershoot is the difference between the baseline and the minimum value in the pulse.
error returns any error or warning from the VI. You can wire error to the Error Cluster From Error Code VI to convert the error code or warning into an error cluster.
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duration is the difference between the falling edge time and the rising edge time at which 50% amplitude occurs.
delay is the difference between the time origin and the time at which 50% amplitude occurs on the rising edge of the pulse.
Pulse Parameters Details
Note The Cycle Average and RMS, Transition Measurements, Pulse Measurements, and Amplitude and Levels VIs provide more measurements than the Pulse Parameters VI, and you can configure each of those VIs.
The waveform-related parameters are slew rate, overshoot, topline (top), amplitude, baseline (base), and undershoot. If y-axis units are volts, then slew rate has units of volts per sample. The time-related parameters are risetime, falltime, duration (width), and delay and are expressed in units of samples.
Note The VI assumes the input pulse or pulse train has a bimodal, or two-state, distribution. Any input other than a bimodal input can lead to inconsistent results.
The Pulse Parameters VI uses the following steps to calculate the output parameters.
1. Find the maximum and minimum values in the input sequence X.
2. Generate the histogram of the pulse with 1% range resolution.
3. Determine the upper and lower modes to establish the top and base values.
4. Find the overshoot, amplitude, and undershoot from top, base, maximum, and minimum values.
5. Scans X and determines the slew rate, risetime, falltime, duration, and delay.
The Pulse Parameters VI interpolates duration and delay to obtain a more accurate result not only of duration and delay but also of slew rate, risetime, and falltime.
If X contains a train of pulses, the Pulse Parameters VI uses the train to determine overshoot, top, amplitude, base, and undershoot but uses only the first pulse in the train to establish slew rate, risetime, falltime, duration, and delay.
Note Because pulses commonly occur in the negative direction, the Pulse Parameters VI can discriminate between positive and negative pulses and can analyze the X sequence correctly. You do not need to preprocess the sequence before analyzing it.
If none of these suggestions help, or if I�m not correctly understanding your issue, please post the software and versions you are using, the applicable portions of your code, and any other information that may help, and I�ll be happy to look further into it.
Have a nice day!
Robert M
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National Instruments
Robert Mortensen
Software Engineer
National Instruments

Extraction of a portion from graph

I have to extract a portion from Graph .
I know the starting and ending point in x-axis and i have to know the y-axis values.
I have used "extract a portion of signal " express VI but am not getting the values correctly.
There is a picture with this, in which the portion in red box is the part i have to extract.
@nk
Solved!
Go to Solution.
Attachments:
Untitled.jpg ‏57 KB

Hi uday ,
Thank you for a fast response .
The VI in the above link shows how to extract a portion of graph with use of cursors. In my VI the user won't do anything . Everything should happen automatically.
First of all.
1.I have detected the peaks in my graph using a peak detector VI. This process have given me the position of peaks in terms of time (i.e x-axis units).
2. I have added a constant offset time like 0.005 sec to each time value and then I provided that value as the starting point of extraction .
3.The length till which the extraction should be done is also kept constant.
4. I just need the amplitude vales of that particular part so that I can use them for my further calculations.
For clear information I am adding a picture of my graph in which the areas I have to extract is perfectly marked inside red box.
@nk
Attachments:
Untitled.jpg ‏57 KB

What's the unit label of y-axis of PSD when using Spectral Measurement Express VI?

Hi:
What's the unit label of y-axis of PSD when using Spectral Measurement Express VI?
Selected Measurement : Power spectral density
Result : dB
No Averaging..
Is dB/Hz the magnitude label of PSD output? Thx!

There could be an issue the the Express VI converting your waveform data into the dreaded Dynamic Data Type, which is just causing more and more memory to be used.
So what I would recommend is use the DAQmx Configure Logging VI to configure DAQmx to stream the data as you read straight to a TDMS file. There are various other properties you can set to make the logging go across files. You just set up the logging before running your task.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Problem: XYGraph with units in one axis in LV7.0

When I bundle one array with units (length) and another without units
together into a cluster and wire it to an XY Graph, the unit label
shows up correctly at the lower-right corner of the X axis.
But when I rescale the unit by changing the unit label (from nm to
uin), the Y axis rescales as well! Furthermore, if I change the unit
label back to nm, the Y axis values to not revert back!
It seems that there is a problem when units are in only one axis of an
XY Graph. (I tried with units on both axis and that seems to work
fine).
Any solution/workaround?
Thanks,
germ Remove "nospam" to reply

In article <[email protected]>,
Philip C. wrote:
> Hi Germ,
>
> Please post the VI that shows this behaviour. Then it will be easier
> for me to troubleshoot.
>
> Thanks!
>
> Philip C.
Philip, I tried to post one, but there's something wrong with my ISP or
some other problem, so I cannot post.
But it's very easy to create: Make two array controls, one for the X
values and one for the Y values. Assign the unit nm to the X axis, and
leave the Y array without units. Make a new XY Graph control.
On the block diagram, bundle the two arrays and connect them to the XY
graph. Go back to the front panel and make "unit" visible in the
graph. A unit label will appear near the lower-right corner. Change m
to nm
Enter a couple of values in each to the two arrays.
Execute the VI. The points will plot on the graph. Now change the unit
lablel from nm to uin on the graph and then change it back. Watch the Y
axis go berserk.
germ Remove "nospam" to reply

Spectral Measuremen​ts - Y axis units?

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Spectral Measurements - Y axis units?