Dial to Calculate Speed

[jtc]

Hello.

I am still stuck with my previous problem of solving for speed using a Dial Indicator. I have a dial with range 0-359 deg. I am taking the difference in time from computer clock (when the dial starts to move and when it stops). Likewise, the distance travelled is the difference when it started to move and when it stops.

But there is an issue on distance travelled that I can't interpret yet in my VI; when it passes the 359 deg.

If say I move from 7deg to 340 deg through 359 section. I actually moved 7 deg + 20=27 deg......(360-340+7=27). 

Similarly, if say I am at 350 deg and stopped at 11 through 359 in this case the formula will be 360-350+11=21.

I want to show this in my VI to accurately calculate for the Speed wherever it pass the dial.

Thank you very much for any help.

[becktho]

Hi Bong

Could you post it as LV8.0? I just want to have a look at it (and give advice if possible ;)).

[jtc]

Hello.

Thank you. Here is the version in 8.0.

[becktho]

I assume you use this vi as a subvi - right?

[jtc]

 "I assume you use this vi as a subvi - right?"

- I plan to use it as a sub VI but at present it is wired in the main VI since i am trial and error yet.

[becktho]

Ok - but I also assume that you get the angle value (represented by the dial) from a hardware measurement (e.g. fieldpoint). Right?

What about the direction? I think you also want to see in which direction the angle changed.

[jtc]

"Ok - but I also assume that you get the angle value (represented by the dial) from a hardware measurement (e.g. fieldpoint). Right?"

- Yes. Its a Magnetic Compass.

What about the direction? I think you also want to see in which direction the angle changed.

- Yes. I showed in another vi the change in direction wherever the compass points.

[becktho]

What range of revolution speed can be expected?

[jtc]

"What range of revolution speed can be expected? "

- about 0.0083 rev/sec. (0.5 rev/min) but it varies in different application.

[becktho]

Have a look at the attached vi - maybe this is helpful.

In general I buffer the angle-differences with the corresponding dt values. The average of these buffered values is then passed to your speed calculation.

On the left side I also check the actual and the last value whether there is a transition 360 -> 0, 0 -> 360 or none of them.

Thomas