analogic input external clock

[orsogna]

Hy,

is it possible to acquire an anlog input at every pulse of an encoder (NI 6221)?

thank you

[Claudio_Guido]

Hi

You can read these forums:

http://forums.ni.com/t5/Counter-Timer/Using-Differential-Encoder-With-USB-6221-and-LabView/m-p/91050...

http://forums.ni.com/t5/Dynamic-Signal-Acquisition/Synchronize-NI-6221-and-absolute-encoder/m-p/7363...

http://forums.ni.com/t5/Motion-Control-and-Motor-Drives/connecting-encoder-DH053-to-USB-6221-DAQ/m-p...

Have a great day

Claudio

[orsogna]

Hy Claudio,

as far as I understood the forums explain the normal way to synchronise the encoder to a analog input that is sharing the same clock and so on. My problem is that doing like this when I have low rpm I have some values of the angle repeated because (i think) the sample clok is too much fast and send in the buffer more than 1 one value of the same angle. Is there a way to connect the encoder so that I can use it as an external clock?or better, is ther another way to solve the problem doing the normal synchronization?

Thank you again

[Claudio_Guido]

If I understood your problem, you can reduce the velocity of the loop that provides Encoder Value, or you can programmatically delete wrong equal values.

[Kevin_Price]

Depending on what you truly need:

1. To avoid duplicate position values, you can do as Claudio suggested and delete them after the fact with some software processing of the measurement array(s).  This will avoid duplicates, but won't directly guarantee an analog measurement at each position change.   You'd pretty much always need to sample at a higher-than-necessary rate and then trim away duplicates.

2. With an M-series board, you can accomplish one sample per quadrature state change directly by using a digital change detection task.  Here's a link to one example, and you can find more by searching variations of the terms "change detection" and "quadrature".

-Kevin P