convert signal encoder to rpm using USB 6251.vi

[ariawan]

Hi, NI

Please solve my problem,

i ve a problem with measuring rpm motor DC using USB 6251..

Pls how procedure that i use?

Can i use function DAQ counter and display this in rpm?(please give an vi example using USB 6251)

Pls reply..

Thanks

[ManLongAtNI]

Hello ariawan,

Here are a few online references.

How Do I Use a Qadrature Encoder with My Data Acquisitoin Board

DAQmx-Measuring Angular Encoder Position

[ariawan]

Hi, user.

i've a problem with my vi

i get TTL signal from my optocoupler sensor and i connect it to PFI 8 dan DI Ground. But data output which i get is 0 and 1 value..

and i hope i get number of pulses(count pulse) as encoding type i used(X1 Encoding).

Is it wrong? whether this fault by its sensor? is it different using optocoupler and encoder as long as signal that i get is TTL(0 and 1)

So, how can i convert this value into (number of pulses/fixed time) and later RPM data?

Here, i include my vi..

Please give me a respond of my work..

i'll appreciate this..

Thanks.

Best Regards,

Ariawan 

l

[ManLongAtNI]

Hello Araiwan,

If you're only measuring frequency try the following example.

DAQmx Measure Frequency with a Counter Input

[ariawan]

Hello, Glen and all

i've measured degree out from my optocoupler using edge count signal..

but i still difficult to convert this value(degree) to rpm(degree per fixed time)..

what i want is like this:

Time |  Position  | Rpm

1       46     14 rpm

2       76     13.5 rpm

3       96      14 rpm

and after this, i want to display the rpm value with waveform chart...

Here i attach my work recently...

i hope i can get the answer...

With Sincerely,

Ariawan

[ManLongAtNI]

How deterministic to do you need the rpm values to be? Judging from your code it heavily relies on software timing. If measurments are taken very minute, you can probably get away with using your existing code and using shift registers to hold onto the last value of the last loop iteration.

[ariawan]

Sorry, i absolutely don't understand what the statement that u said..

May be, can u give me some clue easier..or with some example program..

i just want to know how get the pulses(degree value) in fixed time..how hard i am is to implement the fixed time so that i can convert the degree/fixed time into velocity(rpm)..

Pls..give me some advice...

Thanks...

[ManLongAtNI]

Measure Position and Velocity of Angular Encoder Using One Counter

[ariawan]

Hi ALL,,

i've seen the link that u give to me..

As my picture below..

I've gotten a position value in single sample..

When i use your advice(it's a N sample method that is formed in array and of course it uses sample clock method by ither counter)

So how can i easily develop RPM(velocity) value by its position? and even i get fixed time interval i can't..

~my optocoupler just has 2 output:

TTL signal and ground 

Any comment would be appreciated..Thank

Ariawan. 

[John_P1]

Hi Ariawan,

I think the attached VI might clear things up a bit--this should be what you need, it uses the 2nd counter to generate a clock for the first so you have a deterministic amount of time between sampling the count. 

The VI subtracts the previous count from the current one on every loop iteration.  Since we are using a sample clock, we know exactly how much time passes between each sample so from this we can calculate RPM.  I hope this helps!

Best Regards,