Automated Bode-Magnitude and Bode-Phase Frequency Response Testing of Analog Systems and Electronic Circuits Using Standard USB interfaced Test Instruments

摘要

This paper describes the design, operation and use of a PC controlled automated frequency response measurement system using the standard USB-interface-enabled bench-top test instruments which are now available in most undergraduate electronics laboratories. Being a much faster alternative to manual measurements, such automated measurements meet a need created by the heavy emphasis put on "design" in the electronics curriculum, in particular, in the design of analog circuits with high precision. TheUSB interfaces built in the instruments are employed in the control of the oscilloscope's settings in a synchronized manner with the frequency and the amplitude settings of the signal generator. The LabView code developed increases the frequency of the signal supplied in steps and acquires the amplitude and the phase data of the signals measured by the oscilloscope at both the input and the output of the circuit under test. It creates a data file compatible with Excel for graphing and data analysis. The code also generates Bode frequency response plots on the screen for the user to observe the response of the circuit as the test progresses. The frequency range of our system extends from 0.001Hz to 25MHz. This wide frequency range makes our system suitable for use in testing the very low frequency response range encountered in Controls and Electro-Mechanical Systems, as well as the medium and high frequency ranges encountered in Vibrations, Acoustics, Ultrasonics, and in Electronics.