NI 9423 - Frequency Read VI Help

[mcox53fsae]

Hello,

We are looking to read an 0 - 5V speed sensor into an NI 9423 using a cRIO 9178. We have debugged the hardware and checked to verify that there is an output signal for the sensor using an oscilloscope.

Before moving on to concluding that the module itself may be broken, we wanted to verify that out VI is correct.

Utilizing reference designs for this we put together a VI that will simply read what we believe is the correct channel on the module.

The problem is our is giving us nothing and the module has no LEDs indicating that the module is working.

I have attached a copy of the VI in the hopes that someone can tell us if we are doing something blatantly stupid.

Thanks,

MC

[chaka123 · Accepted solution]

Hi mcox53fsae,

Your VI is not completely wrong, but I do see some details that may not be allowing you to read correctly from the speed sensor.

•  Your DAQmx Create Channel function is set to reading Period, is this the type of measurement you want to perform?
• Your DAQmx Read function is only reading one sample per loop cycle, try reading more samples by changing the type under the function. 
• What range of frequencies are you expecting to read? 
  • Adding a DAQmx Timing function would allow you to have more and better control over how fast you are acquiring data. 
• Finally, the loop has a floating "Wait Until Next ms Multiple function" which is not necessary. 

Also, you may want to take a look at this article https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P8xgSAC&l=en-US. 

Finally, I would prompt you to look at the examples under X:\Program Files __\National Instruments\LabVIEW 20XX\examples\DAQmx\Counter Input. This folder includes examples for frequency measurements and more. 

[mcox53fsae]

Chaka123,

We have figured out the issue. it is actually with the hardware itself. We made the silly mistake of using the NI 9423 when we should have been using another module.

The NI 9423 is meant for 24V industrial logic levels and is not compatible with 5V TTL levels. The minimum voltage for a high level is 11V.

Thank you for the suggestions, we will most likely use these once we get the proper module for our measurements.

Thanks,

Matt