Angular Position Sensor

[mhunt]

I am using a PCI-6251 connected to a SCXI-1001 chassis with a SCXI-1180 and SCXI-1302 terminal block.

I am trying to use an angular position sensor connected to the 1302 terminal block.

The position sensor generates an A,B&Z output, but I am only using the A and B signals.

I am having trouble reading the position. I have the sensor A signal plugged into PFI8 terminal 47 on the 1302 and the B signal PFI10 plugged into terminal 37 and the ground for both signals to terminal 33. I assumed that I had to use the conversion chart from a 68pin cable to a 50pin since the scxi-1180 is a 50pin connection.

I am not reading any signal changes in NIMax, but I see the signals changing with an o-scope.

Any suggestions?

[ryan_d]

Hi mhunt,

It sounds like your signal source is not properly grounded. Table 1 of this tutorial demonstrates different grounding requirements of floating signal sources. Also, this KnowledgeBase article makes some recommendations about which configuration to use when measuring a floating signal source. Please post back if you have any difficulties or if your signal continues to rail.

Have a great weekend!

[mhunt]

Counters use digital signals and I have already grounded the signal through pin 33.

[ryan_d]

Hi mhunt,

It looks like you have everything set up correctly. I think it is a connection problem either from one of the pins or a short in your cable.

First, check your cable for any bent pins, including the PCI-6251 connector and the SCXI-1180 feed through panel.

Second, you can test your cable by creating a pulse output on your PFI lines. To do this, create a new DAQmx Task either in Measurement & Automation Explorer or by placing a DAQmx Task Constant on the block diagram.  Configure the task for pulse output by selecting Generate Signals » Counter Output » Pulse Output. On the next screen select your PCI-6251 ctr0, and on the last page set the Generation Mode to Continuous.

Now you can generate a pulse output example by right clicking on the output terminal of the task and selecting Generate Code » Example.

We need to route the pulse train to one of your PFI lines. This can be done with a DAQmx Channel Property Node. Select the Counter Output: Pulse: Output Terminal property, change it to ‘write’, and create a constant as its input. Select one of your PFI lines (8 or 10) from the pull down menu.

Start the VI and test the line with your oscilloscope. Be sure to test both PFI8 and PFI10. If don’t see any output, try connecting a different cable between your PCI-6251 and the SCXI-1001 chassis.

Let me know if this helps. Have a great day!

Message Edited by ryan_d on 10-03-2007 03:31 PM

Message Edited by ryan_d on 10-03-2007 03:31 PM

Message Edited by ryan_d on 10-03-2007 03:32 PM