OAT Number of Samples per revolution

[MiamiVipul]

Hello:

This is related to OAT Convert to Even Angle Signal VI. I would like to know how I can change the number of samples per revolution. I'm using "Even Angle Reference Signal Processing (Digital Tacho, DAQmx).VI" example and trying to modify this example for my application.

I have a shaft running at 180 RPM hitting an obstruct once at each revolution. Therefore, I need to collect as many samples as possible per each revolution to capture the transient signal. I tried all the combinations of Sampling rates, Number of samples (block size) ect. but when I check the even-angle reference signal, it has the same number of samples per each revolution.

I have NI 4472 DSA card to collect data, using NI 6601 counter to collect Tachometer pulses (720/rev). Attached Zip file contains a collection of modified VIs for my application.

At this point, I'm only interested in the "Even Angle Reference Signal". In other words, I would like to get the best resolution possible for a single revolution of the shaft.

Thank you very much.

[MickeyD]

Hi,

Looking at your post and the example you are discussing it seems that if you increased the number of revolutions in your reading, then you would recieve more samples in the even angled reference signal.

averaged samples (Default)—Specifies that the VI specifies N revolution averaged even angle samples as the reference, where N is the number of revolutions in even angle reference determined by # of revs in reference

The VI is making an averaged signal, so you could have more samples in the average if you were to increase the number of revolutions you averaged over.  Looking at the VI that generated this signal it would be difficult to modify it to just have a larger number of smaples put out without increasing the number of samples available for averaging.  I increasing the # of revs in reference would give you the behavior you were wanting, but I do not know if it is an acceptable way for you to take the measurement.  Let me know if you need any further help or want to discuss more about this example.

Have an awesome Friday,

Michael D
Applications Engineering
National Instruments