Using 9411 Scan Mode cRIO-9074

[Juancar]

Hi,

I am using a NI9411 Incremental Differential Input Module under cRIO-9074 with Scan Mode, but I have noticed that some problems are arising.

My application need two encoder and we select two differential encoders with 1024pulses/rev. I have configured the NI9411 in quadrature Mode, so I can read the position and speed of the encoder. Each shaft rotates at different speed.

One of them can rotate at 4,6 rad/s as a maximum speed while the other one will reach up to 402 rad/s. Then,  the input filter of the module configuration is fixed at 1microsed, the velocity timebase  32768 microseconds and the index mode disabled. Are these values suitables for a correct reading?? The scan rate of cRIO is fixed at 1ms.

On the other hand, looking the NI tutorials (http://zone.ni.com/devzone/eda/tut/p/id/7109) the amount of rotation depends on the encoding type, what kind of encoding is used in Scan Mode? X4?? 

Using the NI Distributed System Manager, one of the encoders read sometimes sporadic pulses (up to 2 counts) although the encoder is stopped. However the other one reads always 0. It seems that the encoder is broken, isn´t it?

Thanks in advance for your comments

[JesusG · Accepted solution]

Hi Juancar,

I think the values are suitable. The issue of reading 0 is explained in this KB:

http://digital.ni.com/public.nsf/allkb/C9088DFDF803CD8B862575F3007C40FD?OpenDocument

Besides, according to that document:

http://zone.ni.com/devzone/cda/tut/p/id/7338

decoding type must be set to X4.

I hope this helps! Suerte con ello.

Jesus

[Juancar]

Hi Jesus,

Thanks for your reply.

I have been doing tests, measuring the angle with two different methods and the results are the same.

The encoder which measured sporadic counts has been substituted by another one and the problem has been solved.

Now all is ok.

Regards

[jeffyy]

I'm currently using the 9411 with the fpga to acquire speed. Am I assuming correctly, that I can configure the 9411 to do the same thing in scan mode? If so can I see an example of this?

Thanks,

JY