Encoder data and speed calculation with PXI 4472B card

[ziasaga]

Hi,

I want to collected time, vibration, encoder and speed signal in one file. I am trying to develop NI by using PXI 4472B and LabView 8.6. Everything is okay but getting only one rpm for speed data. I want to collect continuous data for 15 sec (constant speed) and 15 sec (ramp up speed).

q1. Would you please look into the VI and provide me some suggestions to get continuous speed and all data?

q2. What is the best way (programming etc.) to collect constant speed (100 rpm) and ramp up speed (50-1000rpm) data in two files automatically from one test? Any help?!

New Labview user.

Regards, Niaz

[preston_johnson]

The best method is to calculate speed at each encoder pulse, you then get multiple speeds that will give you the speed ramp up.  We have an excellent set of tools in our Sound and Vibration Measurement Suite, https://www.ni.com/en-us/shop/product/labview-sound-and-vibration-toolkit.html that will calculate speed at each encoder pulse and provide a time stamped array of speeds output.  In addition, the tools will calculate phase and magnitude of vibration at each encoder pulse and provide graphics for bode plot, polar plot, shaft centerline and so forth.  You can actually download and evaluate the tools and examples from the resources tab at the above link. 

[ziasaga]

I already have this suit. Now, please let me know how can I do that.

Regards, Zia

[Chris F]

Hi Niaz,

To answer your questions:

1.  Tachometer processing - Inside the Sound and Vibration pallette, there is an express VI called "Analog Tacho Processing".  That VI is specifically set up to process your digital pulse train, pulse by pulse, and give you a speed profile 

2.  Which file format are you hoping to end up with?  We have a couple of different types: ASCII, TDM, Binary, etc.  The difference is in what medium you wish to open the data.  Will you be opening this in excel after you are done?

Look forward to hearing from you,

Chris

[ziasaga]

Hi Chris,

Thank you for your warm response. Here is the status:

1. I already tried to use 'Analog Tacho processing' sub-pallette. See the attachment, but the RPM value is not the same/similar with the actual known RPM. However, 'Timing trans..' sub-pallette shows similar speed in terms of frequency to actual known RPM. Do frequency and speed profile value in NI should not be the same/very close? Encoder disk is of 60 pulse/rev and using laser TTL to get the pulses, signal input is into 4472B. Does it neet to extra processing to count the edges of rising?

2. I prefer ASCII or TEXT. Experiment is for one ramp-up (50-1000rpm) and one steady (100 rpm) for 15 sec each. I will use this data in Matlab. I am looking for help in programming so that single experiment will divide into two separate files of ramp-up and steady speed. File will consists of time, vibration, encoder value (0,1...) and speed.

Kind regards, Niaz