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Data Acquisition Application Brief


Frequency Spectrum Examples

The Solution

Dr. Beyerlein and colleagues chose to solve the problem with DADiSP, a graphic display data processing software package from DSP Development Corporation. Over the years, using DADiSP has become a requirement for an undergraduate course in engineering. Dr. Beyerlein et al. have developed a three-lab sequence to introduce students to using software in computer data acquisition, harmonic analysis, and data analysis.

Student Lab Equipment

The lab set-up includes a personal computer with a data acquisition card, a Tektronix 2225 oscilloscope, an HP 35665A dynamic signal analyzer, a Tektronix CFG250 function generator, and a Stanford Research SR560 amplifier/filter. Beyerlein and colleagues have written a program called SAMPLER to direct the data acquisition and control functions of the data acquisition board.

Plotting Acquired Data

SAMPLER asks the student for a few parameters, obtains the data, makes a rough screen plot, and then writes the data to disk in ASCII format. Students then use DADiSP to read the ASCII files and display graphs on the screen to which they can apply a variety of mathematical and statistical procedures.

Dynamic Signal Analysis

The dynamic signal analysis labs are part of a Junior-level lab course which introduces about 70 students each fall to methods of measurement and data analysis. Students have weekly lab sessions in groups of about 10 per four workstations, so each student gets to do "hands-on" Digital Aliasing Example work in all three labs. The first lab in the sequence requires students to use a signal generator, an oscilloscope, a PC data acquisition unit, and data acquisition software to gain an understanding of signal levels, resolution, and sampling rate. The second lab adds a spectrum analyzer and filters to acquaint them with harmonic analysis and signal conditioning. In the third and final lab, students are required to integrate the topics covered in the first two labs in an application such as noise reduction, vibration control, or analysis of engine pressure data. The exercises lead them through time and frequency domain concepts involved in the digital acquisition of data, and require them to use DADiSP to examine their data.

DADiSP, an Economic Teaching Tool

Dr. Beyerlein and colleagues say that a data acquisition computer with dynamic analysis software such as DADiSP is much less expensive to use for teaching than an oscilloscope and spectrum analyzer. They also appreciate the great flexibility that DADiSP affords students in examining recorded and imported data. They believe that using this hands-on approach to dynamic signal analysis can "boost student confidence." They also state that students' use of all lab equipment has become "much more ambitious and professional" in the three years since this lab program was implemented. The students themselves appreciate this lab plan most of all, as their course-end evaluations show. They comment, "The in-class experiments and computer demonstrations were particularly effective," and, "More classes should have hands-on work like this one."

The Problem