Custom scale with Create Channel CI Position Angular Encoder

Question

Hi!
In my application I use angular encoders for position measurement. I programatically create channel (task) using DAQmx Create Virtual Channel, CI Angular Encoder instance. Prior to that I use DAQmx Create Scale to create custom scale for the measurement, to convert from degrees directly to meters. The problem is that when I use the task (Start Task for instance) I get the following error message:
Error -200378 occurred at DAQmx Start Task.vi:4
Possible reason(s):
Measurements: Custom scale specified does not exist.
Custom Scale: RowCounter
Task Name: _unnamedTask<66>
Maybe somebody can help me out with this one.
I use the same principle to create custom scales for AI measurements, and everything works without any problems. I know the scale is created properly, as I tried saving the custom scale to max after I create it. I then used the scale without a problem when I wired it as a constant to the custom scale input of the DAQmx Create Virtual Channel vi. It only gives me problems when I create it dynamically, using Create Scale vi.
Some technical info: I use USB-6210 Daq card for signal acquisition.
I will appreaciate any help!
Jernej

Answer 1

Hey!
The error message I get is as follows:
Error -200378 occurred at DAQmx Start Task.vi:4
Possible reason(s):
Measurements: Custom scale specified does not exist.
Custom Scale: RowCounter
Task Name: _unnamedTask<66>
I use USB-6210 Daq card for signal acquisition. The error occurs right after the DAQmx Start Task.vi on the counter task.
As I said, the code runs sometimes without problems and then sometimes it returns an error. I noticed that if I run the CustomScaleProblem.vi on its own it runs ok. When I open the project with mine application, from where I extracted CustomScaleProblem.vi part, and then try to run the CustomScaleProblem.vi, it stops working. It looks like when I open the project it allocates some space which is in conflict with the scale part of the code. Then if I close the Labview environment and open CustomScaleProblem.vi and run it, it runs again without any problem. Well, for now I did a work around the problem by saving the scale in the program and then using it. This approach works fine.
About the arm start trigger. I use it because I dont want the counter to start counting before the AI task starts. I noticed that if I use the AI as a start trigger, and I move the encoder before AI starts, the counter will not start with 0, but will start with a number indicating the encoder movement before the AI start. Is that the right approach if I want the encoder to start
counting from 0 when AI starts?
Thanks and kind regards
Jernej