Creating RPM profile to input into extract waveforms vi

[ARBaker]

I am modifiing a vi in which we are using a NI-9234 cdaq module (4 inputs) and the program reads in 3 accelerometer channels and using 1 of the channels to read in a magnetic pickup to use for a Rpm profile. The speed signal gets sent to analog tacho processing sub vi and generates a RPM profile, then the profile is used as an input to an extract orders subvi. This seems to only work about 50% of the time because of the signal not being very "clean". I have modified the script to allow a voltage level (0-5v) input as the RPM signal and then I have code that then creates the RPM profile from this voltage level. The RPM profile looks exactly the same by looking at it with a probe, but the extract order and compute magnitude sub vi's give problems...I get an out of memory error numerous times when I continue past these dialog boxes my graph that gets updated later in the code does not show any orders. So I'm stumped as to why I get the errors using the voltage level input even though the RPM profile looks the same as the profile that gets generated using pulses to the analog tacho processing sub vi. The RPM profile is just a 2-D array with time and RPM value Am I missing something within the RPM profile that gets included within the analog tacho processing sub vi? There are some screens shots attached showing the code for each type of input.

Thanks for any help

Adam Baker

Cummins Inc.

[mikealder]

Firstly check the inductive speed probe tip to ensure its clean of swarf and the air gap is correct once re-installed.

If you are only after the frequency profile why not extract single tone information to give you the flywheel teeth frequency, divide this by the number of teeth on the flywheel to derive the RPS (rotations per Second) further multiplication will derive the RPM and store this value to your array or am I not reading your query correctly?

You should be able to see the cylinders firing on the engine if you view the frequency information on a chart assuming your sample rate is fast enough, I know I can do this using this technique on a 6BT engine - Mike