# LabVIEW

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## RPM to Position

Hello,

I'm still having this problem and I was wondering if anyone has a solution for me.

I have a shaft rotating at about 600 RPM.  I have an analog signal that jumps to 5 volts whenever 1 revolution has passed.  I do not have a digital encoder setup for this.

I would like to be able to measure the position of the shaft in real time.  Does anyone have a solution?  I have attached my VI.  In the bottom right hand corner i tried to start a for loop that will count time, but it's not working out for me.

Thanks

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## Re: RPM to Position

@kramerfrog wrote:

I have an analog signal that jumps to 5 volts whenever 1 revolution has passed.

I would like to be able to measure the position of the shaft in real time.

You can't "measure" the position of the shaft, you just count rotations on each 5V pulse that comes in.

At 600rpm, one rotation is done in 100msec.

What position accuracy did you expect?

Do you expect to run your LV application at 10ms basis to have an estimated 1/10 turn accuracy?

I can't open your VI since I'm using LV 8.6

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## Re: RPM to Position

I think i should be able to measure the position of the shaft based on previous data.  If i could get a timer to work properly then i could find the real time.

attached is the vi in 8.6

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## Re: RPM to Position

i need to have it as accurate as possible - 1 degree would be amazing.

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## Re: RPM to Position

@kramerfrog wrote:

i need to have it as accurate as possible - 1 degree would be amazing.

600rpm = 1 turn in 100msec

360° = 100msec

1° = 0.278 msec

Do you expect your PC to run at that interval

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## Re: RPM to Position

is that a problem?

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## Re: RPM to Position

@kramerfrog wrote:

is that a problem?

Like Rachel onces said in "Blade Runner" Of course it is!

Message 7 of 22
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## Re: RPM to Position

okay, minus that issue - what about the VI. is it possible to measure the position? There are digital encoders that do this..why can't i do it with an analog device?

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## Re: RPM to Position

labview can sample things at 100khz...i don''t think this should be a problem.  Also the file i posted, the simulated signal i think should be changed to 10000 HZ at 3000 samples.

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## Re: RPM to Position

and the signal should be 8.34 hz. - i uploaded the correct file here again.

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