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02-27-2015 08:20 AM
Hi!
I have an analog inductive sensor hooked up to a rotating shaft that as a screw in it. I'm trying to get the RPM value from the shaft but I'm stuck. I have already implemented someone ells code here on the forum to calculate the total number of revolutions, but not the rpm.
I know there is several ways of getting the values, I have tried to convert my analog signal (0-5V) to a digital square wave (0, 1) so I could then use pulse measurement or tone measurement to get the frequency (w=2*pi/T), with the frequency I can get the rpm. But I didn’t succeed with converting my analog signal to a digital one.
I have also tried to use pulse management and tone measurement directly on the analog signal but I don’t get the right values, reason why is because there is some nose around 0V that the pulse measurement calculate as a frequency, I have tried filtering it away without success.
And I have also tried to use FFT on my analog signal to get the frequency, but nor did I get this to work either.
What I'm I doing wrong? Is there an easier way? I’m I on the right track at least?
Best regards Maurlind
02-27-2015 10:02 AM - edited 02-27-2015 10:05 AM
I'm not sure I understand your problem. It seems to me you were successful at reading the RPM. Is there another question?
Oops, I think you were explaining how you should be able to calcuate it and couln't actually do it.
02-27-2015 10:08 AM
Unfortunately I only have LV 2013 so I can't see your VI.
02-27-2015 12:21 PM
Here is a quick example that I posted on a similar question.
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02-27-2015 02:45 PM
Hi Maurlind. Well, at least some of what you tried should have worked somehow and it should be easier than this. What is your captured signal like? - a nice even waveform or full of noise? If Hoovahh's example doesn't help you, can you capture some of the raw waveform into a tdms file and post it so we can see what the signal that you are trying to analyse looks like. It would make it much easier to suggest a solution which can actually filter out and count the taco pulses.
Stu.
02-28-2015 04:30 AM
Hi Stuart!
I will post som tdm files of the waveform that i get from my signal. Unfortunately I only have acces to my equipment on monday, so I will post it then!
Thanks!
Best regards Maurlind!
03-02-2015 01:39 AM
HI !
Here is the two tdm files and a screenshot of them. The one to the left in the screenshot is the filtered signal with a lowpassfilter, and the one to the right is the raw signal.
Best regards Maurlind!
03-02-2015 06:10 AM
Why not just use a counter to measure the frequecy on the pulses? That would be, by far, the simplest approach to this problem.
03-02-2015 07:01 AM
Hi!
To use a counter, dosen't I need to have that kind of module?
Since I only have a analog input module for my signal, I don't think I could use a counter.
Best regards Maurlind!
03-02-2015 07:50 AM
@maurlind wrote:
Hi!
To use a counter, dosen't I need to have that kind of module?
Since I only have a analog input module for my signal, I don't think I could use a counter.
Best regards Maurlind!
What DAQ hardware do you have? Many of the PCI/PXI DAQ modules have counters on them that you could use.