quadrature encoder as Clock input?...

[humbleANT]

Greetings!

Can anyone give me some advice on using a quadrature encoder as a clock input to an m-series daq?

-Thus accepting A B and Z inputs..

My aplication calls for measuring an Analog input on every rising edge (from the Clock generated) , now I've been scanning up and down the forum -found some posts, mostly concerned with the E-series.

Some pointers will be appreciated!

[Kevin_Price]

You're in luck.  Because the M-series boards support digital change detection (since DAQmx 8.0), you can actually set up a digital input task that's sensitive to both rising and falling edges of both A and B.  This in turn generates an internal "change detect pulse" signal which can be used as a sampling clock for other tasks such as Analog Input.

Here's a link to a posted example with more context found in the associated thread.  I've used this technique to get samples on every quadrature edge too, so I can vouch for it.

-Kevin P.

[humbleANT]

Thanx!

spending some time on the threads... I happen to come across it -was wondering if this was the way to go. Maybe one last question, I've read abit about applying digital filtering to decrease jitter -does it hold true for the M-series? will it be needed -or is it a case of- if you need it use it...

Again, thanx for the advice!

[Kevin_Price]

Hmmm, not sure how to comment.  When I think of "jitter", I think of an undesired variation in time intervals.  I wouldn't think that the digital filtering features would be a very natural way to address jitter.

It may be a moot point though.  Digital filtering can be configured for "PFI" pins on the M-series board, but those pins can't be used for correlated DIO -- only for software-timed static DIO.

I haven't found the need to use digital filtering in quite a while.  Need or lack thereof pretty much depends on the type of sensor signals you have and the kind of electrical environment you're in. 

-Kevin P.