We used and transformed an existing digital measurement system, to implement a virtual instrument able to perform measures in real time.
In fact, the original system was able to perform post-processing only, in deferred time.
Therefore, the first step has been to establish an innovative approach in the use of the existing system units in order to perform real time measurements.
Although the fulfilment of this project led to a use of the system at the limits, with unimaginable performance even from the system vendors,
we succeed in our main goal to perform signal processing in real time.
We could do that, by changing the hierarchy between the different parts forming the system.
For instance, setting the DSP as the master of the communication, and the Macintosh as slave.
The sample transfer has been performed by using the DMA controller of the NB-DSP2300 board in FLYBY Block mode.
This has allowed a throughput of 32MByte/second (i.e. 32 packed samples per second).
Once designed and implemented the communication between the different parts, we implemented the following measurement algorithms:
• IIR filtering.
• FIR filtering.
• Spectral Analysis with classical FFT and related windows.
• Spectral Analysis with a new FFT with phase error correction.
About the IIR filtering implementation, we worked first theoretically for develop just one only and original algorithm, which was able to let us implement our desired filter.
For sure, we developed a flexible algorithm, but we were lucky to use a flexible development tools, LabVIEW.
In fact, in LabVIEW each instrument can be transformed in a graphical icon to be used as a component for a new instrument.
BIBLIOGRAPHY
[1] A.Ferrero, R.Ottoboni A NEW APPROACH TO THE FOURIER ANALYSIS OF PERIODIC SIGNALS FOR THE MINIMIZATION OF THE PHASE ERRORS IEEE TRANSACTION ON INSTRUMENTATION AND MEASUREMENTS, VOL 38, NO. 4, AUGUST 1989
[2] G.Andria, M.Savino WINDOWS AND INTERPOLATION ALGORITHMS TO IMPROVE ELECTRICAL MEASUREMENTS ACCURACY IEEE TRANSACTION ON INSTRUMENTATION AND MEASUREMENTS, VOL 38, NO. 4, AUGUST 1989
[3] National Instruments. LABVIEW 2 USER MANUAL N.I., OTTOBRE 1990, P.N. 320249-01
[4] R.E.Blahut FAST ALGORITHMS FOR DIGITAL SIGNAL PROCESSING ADDISON-WESLEY, READING, MA, 1985
[5] A.V.Oppenheim, R.W.Schafer DIGITAL SIGNAL PROCESSING ENGLEWOOD CLIFFS, NEW JERSEY: PRENTICE HALL 1975
[6] M.Bellanger DIGITAL PROCESSING OF SIGNALS JOHN WILEY & SONS, 1989
[7] E.O.Brigham THE FAST FOURIER TRANSFORM AND ITS APPLICATION ENGLEWOOD CLIFFS, NEW JERSEY: PRENTICE HALL 1988
[8] O.S.Sorensen REAL VALUED FFT ALGORITHMS IEEE TRANSACTION ON ACOUSTIC, SPEECH, AND SIGNAL PROCESSING, VOL ASSP.35, NO. 6, JUNE 1987
[9] G.Guardabassi ELEMENTI DI CONTROLLO DIGITALE CLUP, MILANO 1988
[10] A.Antoniou DIGITAL FILTERS: ANALYSIS AND DESIGN MCGRAW-HILL, NEW YORK, 1979
