RPM sensor integration to cRIO

[GRancourt]

I am currently trying to integrate an RPM sensor from Pepperl+Fuchs (NJ0,8-4,5-N) through a Pepperl+Fuchs 'sensor output interface terminal' (KCD2-E) to my NI 9205 Voltage Module.  I'm working in the cRIO infrastructure; I've got an NI 9023 cRIO controller and an NI 9114 cRIO 8-slot chassis.  I probably don't have it right in my conversion software but what I'm reading from the FPGA raw voltage data doesn't make sense either and that's my focus right now.

If I'm reading the data sheets correctly (Definitely not an EE), the following is true:

1. I'm supplying 11.8 V to the KCD2-E terminal (Across 5+ and 6-) with the understanding that my output will go from 0-10 V.  
2. The terminal supplies 8 V to the sensor.
3. I've wired the terminal as an RSE connection (confirmed in the module properties of my LabVIEW project) with Output 4- as the signal line and 6- as the common ground between my module, the chassis, and my power supply.

I've double checked all of the wiring with the continuity function on my multimeter, i.e. all grounds go where they should, output is connected to the NI 9205, etc.  I've also used the DC voltmeter function across the signal and ground pins on the KCD2-E to check what the input to the NI 9205 should be and it's a nonzero input (~1/sqrt(2)).  

I've attached my FPGA.vi file but all it's doing is reading directly from the cRIO and outputting to a numeric indicator with a six-digit floating point.  Even if the sensor voltages are small I should be picking something up with that kind of precision.

All of my other sensors in the package read noise when I don't have sensors plugged in except for the thermocouple values which tend to settle after enough run time.  The RPM sensor raw voltage data reads 0.000000 or +1.000000 and never vary.  Going up a level in the program to the user interface (GetData.vi) that calls FPGA.vi I can see my sensor reading is a solid line never wavering from the center of the chart it outputs to.

So basically I have a couple of questions.  Did I incorrectly wire my sensor?  Is the way I've extracted the voltage from the chassis incorrect?  And how do I convert the voltage to RPM (it's not clear to me what the upper value is for the RPM sensor)?  I've tried everything my brain can come up with so any ideas would be greatly, unequivocally, stupendously appreciated.

Greg

[Drew_T]

Greg,

I am sorry that you are experiencing difficulty.  What pins are your RSE inputs connected to?  

If I understand correctly, the part you are looking at is a proximity sensor.  Is this correct?  In this case, I would assume that it will provide an increase (or decrease) in signal when an object is in proximity to it.  If you have the sensor measureing an arm on a shaft for instance, you would get one peak of voltage for each rotation.  Then you would simply need to count the pulses to determine frequency.

Finally, to test the input of the NI 9205, you can do a "Battery Test".  To do so, simply connect a known voltage (within the specs of the 9205) and run the FPGA VI.  This way you can determine whether the input signal is bad or something else is amiss (perhaps you've wired it incorrectly).

[GRancourt]

Drew,

I appreciate the help.  I think I'm going to rig a wire to send the output to an oscilloscope so I can see exactly what's happening.  I think you are right that the sensor actually just pings when something gets close to it.  How to program the counter should be fairly straightforward; I've just got to figure out what the output is.  Thanks again.

Greg