Newbie - Waveform Peak Detection - Location Mean

Hi,
I'm trying to implement a magnetic speed sensor in my project, this speed sensor produces a signal like this:
(Image from this site)
For now I use this to simulate the sine wave:
I was trying to build an application that:
- Read my measurement file.
- Detects the sine waveform peaks
- Calculates the mean of 10 locations values
But with no success...
Any help? Thank you
Sorry for my bad English.
Attachments:
1. Sine Waveform Generator.vi ‏48 KB
2. RPM.vi ‏36 KB

If you go to toolbar and help. And then select find examples. You can do a search for peak. Labview is shipped with many good examples. It is often quicker then ask for help in this forum
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)

Similar Messages

Does anyone know why the waveform peak detect function provides accurately the position of the peaks but not the value?

Does anyone know why the waveform peak detect function provides accurately the position of the peaks but not the value?
I have been looking at my data at the position indicated by the function as a peak, and it is correct at that place the wave has its peak, but the value provided by the function is higher than the actual value at that point.
Attachments:
Test.jpg ‏53 KB

The help makes it clear that the VI will make a quadratic fit to the data, so the locations are not integers (i.e. not aligned with you exact data). From that analysis, the peak is between two of your points, and slightly above the neighboring data.
See the coercion dot. Make the "locations" array DBL (Why did you change it to I64, that makes no sense at all!)
Quote from the help:
"Locations contains the index locations of all peaks or valleys detected in the current block of data. Because the peak detection algorithm uses a quadratic fit to find the peaks, it actually interpolates between the data points. Therefore, the indexes are not integers. In other words, the peaks found are not necessarily actual points in the input data but may be at fractions of an index and at amplitudes not found in the input array."
All clear?
LabVIEW Champion . Do more with less code and in less time .

6i can't find waveform peak detection vi. Load error code 20

6i can't find waveform peak detection vi. Load error code 20

The waveform peak detection VI is found only in the Full and Professional development systems. Do you have the base package?

Waveform peak detection ...Please have a look

Hi folks,
I am trying to acquire 2 signals and then detect the peaks of each of them and divide the peaks and display it in a waveform chart.But my Peak detection doesnt work at all...I tried plugging in values from 3 to 10000 but it just doesnt work...Please have a look at my VI and feel free to point out any errors in my VI..
Thanks
Attachments:
slope 2 channels3.vi ‏51 KB

Hi,
Had a look at ur VI
tell me, do u need a single peak for every iteration or a series of peaks above a certain threshold?
If it is a single peak for each acquired waveform , then extract y array from the waveform cluster( you have already done it in ur VI) and connect it to 'find array min max' function found in array functions palette and u get the single peak for each waveform.
If it is a series of peaks u are interested in, then compare all these values inside a for loop.
Index each element inside a 'for' loop, check it for threshold using a conditional case structure and put it inside a shift register.
regards
Dev

How to measure error on peak detect?

Hello!
I'm using the vi Waveform Peak Detect to find peaks in some signals that we analyze at the lab where i work. However, i must know also what's the error on the measure. Anyone knows if there is a vi that measures peak AND the error on the values found? Or at least a mathematical way to find the error myself?
Thanks!

This is not an simple question to answer. When you search for the peak value of a signal you have to make some assumptions about that signal. For example if your signal looks like [1, 1, -1, -1, 1, 1, -1, -1, ...], it may be difficult to define its peak value.
The first approach is, that your signal is a square wave of amplitude 1.0 and normalized frequency = 0.25. It this case the peak value is also 1.0
But the same signal could be the result of the sampling of a pure sine tone of amplitude 1.4142 (SQRT(2)). if you sample your sine tone at 45, 135, 225 and 315 degrees of phase, you get the same sequence of samples. In this case you would like your peak result to be 1.4142.
So the error can be as big a 41% (3 dB). This is of course an extreme situation, and
in most case the error is much smaller.
In general, the higher the relative bandwidth of your signal is (the ratio between the signal bandwidth and the used sample rate), the most uncertain is your result. So if you want to "stay in control" you need to make sure your signal is sampled at a rate that is high enough to give a good representation of your original analog signal.
As an option, you may want to re-sample your signal (to a higher rate) using an appropriate algorithm. The new resampling VIs offer various interpolation algorithm that you can experiment with, depending on the nature of your signal. The peak detection VI will then do the work for you.

Peak detection method

Hi,
Can anyone recommend the best method to use for peak detection incoming
array of data (represents ECG).
I would like to use the 2nd deriviative method, any ides if its
recommended, and how best to use it?
Thanks

There is a vi called "Waveform peak detection.vi". You set a threshold to detect peaks or valleys.
www.vartortech.com

Peak detection from waveform data

Hi Folks.
This is probably an obvious one but I cant figure it out. In the sine wave detector VI attached the peaks are determined from a simulated signal. I want to be able to do the same with a waveform data (DBL) but it wont let me. How can I extract the signal from the DBL to feed to the rest and make the waveform peak detector VI work right??
Thanks,
Mark.
Solved!
Go to Solution.
Attachments:
Sine Wave Detector 2009.vi ‏140 KB
waveform peak detector.vi ‏40 KB

Use From DDT, found on the Signal Manipulation Palette, to change the Dynamic wire into a Waveform.
Bob Schor

Peak detection( take 100 ms samples?)

Hi...
I have a problem using peak detection under Analysis=>waveform monitoring.
I want to get the real data (ECG data), and detect the peak of the data. Then i want to store the index of the peak into array so that i can measure the time difference between two peaks.
my problem is that when i use peak detection, i cannot get the result as above mentioned. Before this i have tried to test the peak detector and found that if it will detect the peak for 100 ms time interval only. SO if i have waveform with f=100 Hz, then it will detect only 10 peaks..Is it correct that this vi takes 100 ms sample for detection? *correct me if i'm wrong
And since i want to get the real data from ECG hardware, is there any method to measure index of the occurence of all peaks and store it into array? (not only for 100 ms)
-I saw the formula in peak detector help :
To view the locations in terms of time, use the following equation.
Time Locations[i] = t0 + dt*Locations[i]
What does [i] here represent?
Thanks for the help...
Regards,
Rismi *newbie...:d

Hi...
Thanks, now i can understand about peak detection for simulate signal...
Then if i use this vi to detect peak of ECG data(data from DAQ or recorded data)..This vi will detect the locations of peak of current block of data. what "current block of data" in this case represents..??
i attach my simple program to detect the index of peak of my data. But i cannot get my desired result. And when i detect the number of the peak, the values is either 0 or 1. I don't know how to fix this problems.Can anyone give me advice?
Attachments:
retrieveSunday22.vi ‏161 KB

Problem in peak detection

Respected sir/madam,
i am actually processing human radial artery pulse signal... i acquired that signal and linearised that by using filter...
there is a problem in peak amplitude detection and location...by manually we can say there is more number of peaks ..but peak detector shows only 25 peak's amplitude and their locations...i can't understand about locations that shows..i attached the data which is in .lvm extension and the vi
please help me to rectify the problem..
thank you
Attachments:
Untitled 2.vi ‏100 KB
Untitled 2.vi ‏100 KB

Once again the Dynamic Data Type (DDT) generated by the Express VIs hides the real problem.
The data segments are too short to reliably detect the peaks - not every segment has a peak and some peaks may be partly in one segment and partly in the next. By combining all the data into one waveform before filtering and peak detecting, it is possible to get reliable matching between the "eyeball" peak detector and the software peak detector.
Note that the large transients at the beginning of the data set are detected as peaks. These transients are due to the real transient in the data and the transients of the filters. I did not attempt to remove them. You could use Array Subset with either manual selection of the end of the transient or some automated process based on the larger amplitude and lower frequency of the transient compared to the real signal.
There is a lot of "stuff" in this VI - things I tried and did not remove and multiple ways of doing things. The enabled diagrm of the Diagram Disable structure has a constant with the data from your file so that I did not need to read and process the file repeatedly while working on the filters and peak detector.
Comments in no particular order regarding what I did and how the posted VI works.
1. The DDT data from Read from Measurement File.vi is converted to an array of waveforms. The Waveform data type is well docmuented and the internal data structure is readliy accessible.
2. Each element of the array of waveforms from Read from Measurement File.vi is appended to the corresponding element from the previous iteration to form one array of waveforms containing all the data in the file. This is displayed on Array of Waveform, Array of Waveform 4, and Signals total. Note that these are graphs, not charts. The data is also put into 2D arrays as Array of Waveform 2 and Array of Waveform 3.
3. I do not have Advanced Peak Detector PtByPt.vi, but I think the data is not truly point by point so this may be a poor choice.
4. I used the standard filter VIs (rather than Express VIs) to stay away from DDT. The outputs are slightly different, but the Express VIs do not give you complete control or knowledge of what the filter setup is. I used Butterworth filters for both filters and adjusted the cutoff frequencies slightly to get similar waveforms.
5. I used the standard Peak Detector.vi from the Signal Processing >> Signal Operations palette. It reliably finds 104 peaks over a wide range of widths and some variation in thresholds. That count includes the transients at the beginning as mentioned above.
The .2 VI contains all the junk code I described above. The .3 VI is a cleaned up version.
Lynn
Attachments:
Untitled 2-9.2.vi ‏760 KB
Untitled 2-9.3.vi ‏183 KB

2 Channel peak detection and value look up

Hi all,
I have 2 different sin waves going into channel 1 and channel 2 of an oscilloscope. What I'm trying to do is:
1. From Channel 1's input determine the time when peak values occur and save them to an array
2. Then find out what channel 2's voltage output is at times determined from step 1.
I started doing this project by only using 1 channel where I was able to extract the y data as well as plug it into peak detection.vi.
However after I merge the two channels together and proceed like I did with 1 channel labview shows disconnected wires due to data incompatability.
Any help would be greately appreciated on how I can locate channel 1's peak times and plug those time values to determine output values for channel 2.
Attached is
1. The single channel peak detection (which works)
2. 2 channel peak detection (the .vi I need help on)
Attachments:
Single Channel Peak Detection.vi ‏33 KB
2 channel peak detection.vi ‏22 KB

The VI is broken because you are connecting an array of waveforms with VI's that are asking for a single waveform. You need to use Index Array to break out one or the other waveform to feed to the other VI's.

Need Help with peak detection

Hello,
I am in need of some help using the peak detection. I have an array of values that I need to find the centroid (peak) of. I am only interested in finding the centroid of a large peak. The problem I keep having is that the peak detection VI finds every little peak above the threshold when I really want the overall average peak. Please look at the graph in the picture file to see what I mean.You can see that the main peak has jagged edges. The peak detection in Labview will find every one of these jagged edges and report the location back as a peak. I am only interested in the overall shape of the peak. How can I filter out the multiple peaks and only report the centroid of the desired shape? There is an example program in the labview package called "advanced peak detection point by point" but I cannot figure out how to employ it in this application.
Thanks in advance for any help.
-Mark
Attachments:
Array values.PNG ‏9 KB

If I were you, I wouldn't even use peak detection.
The point of peak detection is to find multiple peaks, like in a sine wave, etc.
If you just want the maximum:
Just use 'Array Max & Min'
The 'max value' equates to your y-value.
The 'max index' can be used to find your x-value
Message Edited by Cory K on 05-07-2009 11:52 AM
Cory K
Attachments:
Peak.PNG ‏3 KB

Peak Detection Specifics

A part of a fatigue testing data acquisition program requires peak detection. I've read the other peak questions on here, but mine seems to be different.
Each cycle, I collect n points. Within that, there are x peaks. The data between peaks 1 and 2 is extracted, potentially saved to disk, and always inserted into a circular buffer. This continues for each peak found. Of course, there is always data left after the last peak that does not get included into a cycle. So, I shift register it back to the next data collection loop, and append it to the beginning of the next set of data.
My problem is that peak detect doesn't seem to find the peak if it's the first point in a data set. This seems to happen regardless of settings that I use. I c
an't change threshold values, and any width seems to have the same result - skipping the first point. Consequently, all the data that got held over from the last cycle gets discarded because the first peak is ignored.
Anyone have any ideas? I'm reinitializing the peak detection system each cycle because if I don't, it screws up the location indicies. I may put together a picture later, the whole problem makes more sense graphically.
Thanks!

The peak detection requires a peak (data on both sides of peak). Since the first point of the data does not have points on the other side of the peak... I would suggest that you keep more points before the peak as your remainder waveform and it will then pick up the peak. The number will depend upon your peak width spec.
Stu
Stu McFarlane
Viewpoint Systems, Inc.

Peak detect error

Hey guys.
I have a problem with my peak detect on a Power spectrum signal. from http://www.ni.com/white-paper/4278/en/ I know that
I would like to have f = 1 meaning that the frequency at which the acquired time-domain signal was sampled (Fs) has to be equal to the number of points in the acquired time-domain signal (N).
When i try to do this the peak detect returns the error 20013 the width must be greater than zero and smaller than sample rate.
this makes no sens to me ?
When i have Fs = N x 10 it runs.
I have added the VI that i have problems with ! if you need the whole project I will gladly add that to.
Attachments:
Both sensors.zip ‏329 KB

Hi Genex,
instead of that huge VI you should attach a smaller one, that demonstrates the problem! Right now we would need your DAQ setup to generate a signal to be able to try that VI...
So please:
Generate some typical waveforms, make them default in a waveform control and attach a VI with those waveforms and a typical call (with all your parameters) of PeakDetector!
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Any app in OS X Mavericks unable to detect location after updating

I'm using MacBook Air (late 2013) & OS X Maverick 10.9.3 on it. I'm facing to this problem since I updated to 10.9.2 from 10.9.1.
Like no any app from Maps, Twitter, Facebook is able to detect location. Earlier it was able to. Mean, when I click on Current Location button nothing happens on Menu bar earlier there used to appear sign like this (➤). I connect to internet strictly through the WiFi so not any problem with that. In Systm Prefrences Location service is also enabled. So very frustrated, Please help me.

2 things you could try.
1. If you go to Google Maps, is that able to locate your location?
2. Do you have access to another computer or smartphone that can use your wireless network to determine your location, without relying on cell towers? For example, if you have an iPhone, if you put the phone into airplane mode and then turn the Wi-Fi back on, it will only search thru your wi-fi network. Can it determine your location by that means? If so, at least the Wi-Fi router can be discounted as part of the problem.

Block Peak Detection and Display

I am doing a project on a spike check automation program in Labview. I am trying to detect the peaks and valleys from a probe test on a wafer.The probes are attached to the wafer and connect to an oscilloscope. Right now finding the peaks and valleys are done manually but take a lot of time from one pin.
My program has to optimally run for 20 seconds and, at every interval, of let’s say 20microseconds, has to take the worst case scenario for the peaks and take the screenshot from the oscilloscope and save it until the worst case scenario in the next block on 20 microseconds until the 30 seconds are up.
I am using LV 2010 and I don’t have experience with LV before. I have researched and found a VI called waveform peak detector which seems helpful but I am not sure how to save a screenshot at each interval or block.
I am also unsure on what to put in a loop so my program can run continuously for 30 seconds without stopping. I also have the instrument drivers for my particular oscilloscope so I can control the scope from my computer and LV program.
Any help is appreciated and thanks in advance for your assistance.

Share for care... oops share for cure...!!
please share your code or more info..!!
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Newbie - Waveform Peak Detection - Location Mean

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