Filter Frequency Fluctuations

[Marshman]

I have a RPM sensor that outputs 0 - 5V pulses to my DAQ.  I am having trouble with fluctuations in my frequency output. I confirmed with an oscilloscope that the sensor is working with minimal noise, so I know the noise is coming from within my LabVIEW program. Does anyone have any suggestions as to how I can minimalize the noise?

Thanks

[Marshman]

I have a RPM sensor that outputs 0 - 5V pulses to my DAQ.  I am having trouble with fluctuations in my frequency output. I confirmed with an oscilloscope that the sensor is working with minimal noise, so I know the noise is coming from within my LabVIEW program. Does anyone have any suggestions as to how I can minimalize the noise?

Thanks

[HollyBerry]

Have you tried plotting the data before the Timing and Transition Measurements express VI? What is the purpose you are trying to get out of this express VI? Try measureing the frequency in Test Panels within NI Measurement and Automation explorer. Do you still get jitter?

[johnsold]

What speed is your system running? How many pulses per revolution does your sensor generate? What is the minimum pulse width at the maximum speed?

And, as Holly asked, please show us the the data coming from the DAQmx Read.

Lynn

[Marshman]

Before the Timing and Transition Measurement express VI the data plots just fine.  The only purpose of the express VI is to obtain the frequency of the signal, is there a better way to do this??  I did measure the frequency using the test panels and its exactly what it should be.

[Marshman]

My system is running between 400 - 1800 RPM with one pulse per revolution

[HollyBerry]

Maybe there is jitter thrown in by the automatic LabVIEW conversions(indicated by the red conversion dots on the input terminals. I would try to Convert to Dynamic Datatype (the datatype that express VIs use) and then convert from Dynamic Datatype when you read the data. I would also recommend wiring your error wires through the express VI to see if there are any errors being thrown.

Please let me know if this helps you out!

[Marshman]

I tried what you said but I am still getting significant fluctuations in the frequency.  The signal coming in is very clean but for some reason labview is not able to make sense of it.  What do you suggest next?

[HollyBerry]

Which test panel are you using in Max that is giving you the frequency measurement you would like? As I re-read your first post, it sounds like you are using a digital signal (0-5V pulses) and it would make more sense to use a Counter Frequency task (rather than Analog Input) to measure the frequency. 

[Marshman]

I am just using an analog input test panel, my hardware only allows for analog inputs.  My I/O is NI 9207.

[Dennis_Knutson]

I don't see anyplace with the test panel that returns the frequency. Please create an indicator for the DAQmx Read, run the VI until you see data, go to Edit>Make Current Values Default, save the VI, attach the saved VI.