Capturing high speed encoder data

[serkanb]

Hello,

I have a motion control project where I would like to record position data. High speed capture is limited with 2Khz sample rate. But I have to record at much more higher speed. 

I read that there was another option which is connecting the motion control card (I am using a PCI 7358) and the DAQ card by using a RTSI cable and routing the A and B channels of the encoder to the DAQ card using the RTSI lines.

I have 6143 and 6280 DAQ boards, PCI 7358 and a RTSI cable. 

Q1. Which card is better to use? 6143 or 6280?

Q2. When I examine examples, I saw that its possible to route phase A and phase B signals of an encoder to the RTSI line with Signal Select.vi. But I couldn't find an example about how to read them from DAQ Card.

Q3. How could I obtain position information from encoder's phase A and phase B pulses which is acquired from DAQ card?

Regards

[John_P1 · Accepted solution]

Hi serkanb,

The 6143 does not have support for quadrature encoder measurements (although you may perform an edge count task and use the B signal as an up/down line to get a similar effect).  If interested, more information can be found here (the 6143 uses the same STC I ASIC that the E Series DAQ devices do).

This doesn't really matter too much since you have a 6280 which does support quadrature encoder measurements (it uses the STC II ASIC).  To answer your direct questions:

Q1.  The 6280 is better (see above)

Q2.  You need to use a DAQmx Channel property node to select which terminals to use for your encoder task:

Q3.   I would start with a shipping example:

Help >> Find Examples... >> Hardware Input and Output >> DAQmx >>  Counter Measurements >> Position >> Measure Angular Position.vi

You would need to insert the property node before the Task is started (but after the channel is created).

I hope this helps, if you have any questions don't hesitate to post back!

Best Regards,