Low frequency measurement with the NI-4552

[bajaf]

Question 1. I have the NI PCI 4552, I´m trying to measure low frequency signal comming from an electric signal and from an accelerometer. Using the SVXMPL_SUBSETFFT(DAQ).vi is possible to measure frequencies up to 20 Hz, what modifications I have to make in this program to measure frequencies under 20 Hz ?

 Question 2. When I write a program to avoid to use the previos one, I use the C-SCAN rutine, but this produces a delay in the measurement, then I have to Windowing the signal, where I have to allocate this module (Windowing) in my program?

Question 3. How I can export the signal acquired, I mean for example as a figure in wmf format ?

[AllanS]

Hello bajaf!

I have opened the example program you have refered and I have some follow up questions.  First there are no programmatic changes that will need to be made to measure signals 20hz in below.  In general as long as you are sampling at least 2x (usually more like 5 to 10x) faster then the fast the frequency component of interest you will successfully acquire the signal.  You will also want to set the start and stop frequency, on the VI, accordingly.

Could you elaborate more on question two.  I am not sure I understand what you mean.

On question three do you mean you want an image of the graph, such as a jpg or bmp?  If so you can do this by using the report generation VI append control image to a report.  This will allow you to create a report that will include the graph.  If this is not what you are refering too let me know.

I want to make sure I provide you with the help you need to please let me know if I am not understanding you questions.  Have a great day!

Allan S.

National Instruments

[bajaf]

Thanks you Allan, I´m going to review the way I´m measurging and will send you the experiments. I´m going to precise question two.

Thanks again, greetings

bajaf

[AllanS]

Sounds good.  Let me know if you have more questions!

Have a great day!

Allan S.

National Instruments