convert encoder signal to rpm

[ariawan]

i've a problem with my function in labview to convert signal encoder to RPM..

Signal encoder has on off voltage (0-5 Volt) but i actually have made signal conditioning from signal encoder to data digital(rpm) with hardware i designed..and it can display..(rpm value)

and my idea is to move that data to my labview(waveform chart), so i can make program for next step...

i've enter it to counter input and digital input,,it can't be displayed and error..what should i do for this??

My DAQ type is USB NI 6251..

Please help soon..what step should i do for these problem??

And how the best way to convert this signal(encoder signal) to rpm???

Message Edited by ariawan on 01-04-2010 10:56 AM

[Nate.H]

Hi ariawan,

Please review these resources, as they will describe how to correctly connect a quadrature encoder to a DAQ card counter input to measure encoder counts.

Quadrature Encoder Measurements: How-To Guide

http://zone.ni.com/devzone/cda/tut/p/id/7109

How Do I Use a Quadrature Encoder with My Data Acquisition Board?

http://digital.ni.com/public.nsf/allkb/C6C6632A54DBA7DD86256275005E18E2?OpenDocument

Once you are able to successfully read encoder counts (use on of the DAQ counter shipping examples to test) you can then convert the counts to whatever unit of measure you desire. If you are looking for RPM, then take the formula for rotational position given in the above How-To Guide, and compute then change in rotational rotation between two measurements. With the change in position, and the time interval over which it occured (time between measurements) you can easliy compute the rotational velocity and convert from degs/sec to RPM.

Best Regards,

~Nate

[ariawan]

hi...

There some questions..

i use optical encoder for this project..what is the method same??

i still confuse with converting signal waveform(encoder signal) to RPM..?

please give me some example how to convert that signal to rpm...

thank, ariawan. 

[Nate.H]

Hi ariawan,

It depends...what kind of signal does your optical encoder output? How are you currently trying to perform the conversion? Where specifically are you getting stuck?

Best Regards,

~Nate

[Jochen]

Ariawan,

I think the most important point is not to use an analog input to acquire the encoder signal, but a counter, which provides good methods like frequency measurement or buffered position measurement to get the velocity value.

Regards,

Jochen