NI 9401 + cRIO 9082 speed measurement

[franz94]

Hello!

I want to measure a rotational signal with the NI9401 and cRIO 9082. For testing i am using a signal generator and it is connected to Mod5/DIO0. In the FPGA I want to measure the rising edges. (see attached picture) With them I would be able to calculate the rpm. But my code doesn't work: The counter counts up constantly even I have no signal generator connected. What is the problem?

Thank you in advance.

Best regards

Franz

[preston_johnson]

Here is a good design document that may help. 

http://www.ni.com/white-paper/3230/en/

Figure 3 in the above white paper, uses the FPGA clock to determine the time between digital input events.  This is not a counter example, it simply uses the DIO to give the current state of the line. 

Further down the white paper is a conversion VI to RPM. 

Hope this helps. 

[franz94]

Hello!

Thank you for your answer. I have tried it and it works, but only with an analog signal. but i have an digital one... Now i found an interesting tutorial (Point 4): http://www.ni.com/white-paper/14549/en/#toc4

There they wrote, that i can find the example in the example finder under Hardware Input and Output >> CompactRIO >> FPGA Fundamentals >> Counters >> Frequency Measurement >> Count and Period – cRIO.lvproj., but in my labview version (2015) I can't find this example. Do you have an idea where I can download it?

Thank you in advance.

Franz

[Christoph_D · Accepted solution]

Hi Franz,

I didnt find the examples in LabVIEW version 2013, but in 2012 you can find them. In general you could just download the version as a evaluation and get the examples. Since I found the examples in a VM youc an find the examples attached to this post.

Besides that most examples are a restructured in the newer LabVIEW versions but the general topics are still there.

Best regards,

Christoph

[franz94]

Hello!

Thank you very much - it works

Now I'm able to measure the rotational speed.

best regards

Franz