RPM,of a wheel with 8 point ,read by proximity and FP DIchannel .

[nicola]

I have a wheel with 8 metallic sector (one for 45°) and one proximity capture the presence of sector.I would like perform the Field point for read the RPM of the wheel.
My proposition is in the attached VI.This capture the front side level Hight by the read of previous state and the present state of Prox. (By shift register).
But the RPM is not linear.
What's the best solution for this work.
Thank Nicola.

[AndreOliveira]

Hi Nicola,

It seems that you want to use FieldPoint hardware to measure the frequency of a signal. The option for you would be either FP-CTR-500 or FP-CTR-502, you can find information about these modules in the following link :

http://sine.ni.com/apps/we/nioc.vp?cid=2198〈=USNI

http://sine.ni.com/apps/we/nioc.vp?cid=4350〈=US

Be aware that the choice you are going to make, whether use FP-CTR-500 or FP-CTR-502 will depend on the kind of signal you have to provide to the module, if it is a sinking or sourcing device.

Regarding the VI you have attached I could not see the relation between your program and FieldPoint hardware, if you really want to use FieldPoint hardware you will need to install Fieldpoint Explorer (software hardware for the
fieldpoint) and by doing that you will get a LabVIEW shipping example program called "Frequency Measurement.vi" that will perform the measurement you need, once the module is appropriatelly set.

Best Regards

Andre Oliveira

[nicola]

"Hi ANDRE,
Thank for your answer
Sorry but I don't have specified the application.I utilize one channel of field point FPDI dual channel module.The software for communication with the Field point explorer is in the other subvi, the attached VI is only for the transformation of signal input (by FP channel).
Kind Regards
Nicola Bavarone"

[AndreOliveira]

Hi Nicola,

I would not recommend the FPDI dual channel module because this is a digital input channel that needs to be poll by the application in order to receive the new state of the channel, if you are trying to measure frequency you would need an input that does not need to be polled by the application program.

Your option would be work with counters as opposed to regular digital input channels.

Andre Oliveira

[nicola]

Dear Andre
I'm aware of the fact that a software polling is needed, but the frequency to be measured is so low that I reckoned this kind of soluttion as feasible. the wheel turns at a maximum speed of 20rpm, therefore I can simply don't care of the acquiring time.
what I'm pursuing is the better software solution to obtain an estimate of the average speed; I don't need an absolute precision on this data.

Nicola.