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

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2015 ASEE Annual Conference & Exposition


Seattle, Washington

Publication Date

June 14, 2015

Start Date

June 14, 2015

End Date

June 17, 2015





Conference Session

Instrumentation Division Technical Session 3

Tagged Division


Page Count


Page Numbers

26.271.1 - 26.271.12



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Paper Authors


Mustafa G. Guvench University of Southern Maine

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Dr. Guvench received M.S. and Ph.D. degrees in Electrical Engineering and Applied Physics from Case Western Reserve University. He is currently a full professor of Electrical Engineering at the University of Southern Maine. Prior to joining U.S.M. he served on the faculties of the University of Pittsburgh and M.E.T.U., Ankara, Turkey. His research interests and publications span the field of microelectronics including I.C. design, MEMS and semiconductor technology and its application in sensor development, finite element and analytical modeling of semiconductor devices and sensors, and electronic instrumentation and measurement. He can be reached at

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Mao Ye University of Southern Maine

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Mao Ye is an electrical engineering student at the University of Southern Maine, and an equipment engineering intern at Texas Instrument, South Portland, Maine. He also worked at Iberdrola Energy Project as a project assessment engineering intern. Prior to attending the University of Southern Maine, he served in the United States Marine Corps as communications chief. His area of interests are microelectronics, Instrumentation, software development, and automation design.

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Automated Frequency Response Testing of Analog Systems and Electronic Circuits with USB interfaced Standard Test InstrumentsThis paper describes the design, operation and use of a PC controlled automated frequency response measurementsystem using the standard USB interfaced bench-top test equipment available in undergraduate electronicslaboratories. Being a much faster alternative to manual measurements, such automated measurements meet a needcreated by the heavy emphasis put on "design" in the electronics curriculum, in particular, in the design of analogcircuits with high precision. In the implementation of such high precision circuit designs, in order to achieve therequired level of precision, many design iterations (i.e. design+simulate+verify+protoboard+test+if not passingspecs, redesign) are needed, therefore forcing a quick turn around time in order to fit such design experiments intothe limited hours of weekly laboratory schedule. This system can also be employed for the frequency responsetesting of any form of analog or control systems including electro-mechanical systems and in vibration testing [2].The automated frequency measurement system reported here employs a standard set of bench top instrumentsconsisting of a Tektronix Oscilloscope (Model TDS 2024C), a Tektronix Arbitrary Function Generator (AFG3021C) and a Tektronix Digital Multimeter (DMM 4040) all with USB interfaces, and a Tektronix Triple PowerSupply. Expensive GPIB (IEEE 488) interface cards and cables are not needed. Recent availability of USBinterfaces in affordable instrumentation make implementation of automated tests possible even in undergraduatelaboratories with limited budgets. The control software has been developed in LabView environment but it is anexecutable file, therefore portable, and can be distributed and run on any Windows based computer includingstudent owned laptops. The code can be adapted for other instruments with USB interface, and will be madeavailable to share with faculty in other institutions.In the frequency response measurements of a circuit magnitudes and the relative phase of a signal applied to theinput and the voltage appearing at its output of a circuit have to be measured. To measure a frequency response, thesignal frequency has to be stepped, the measurement being repeated at every step to gather data points to plot theresponse as a function of frequency. Input and output voltage amplitude measurements can be accomplished verysimply by employing two AC voltmeters. However, most undergraduate teaching laboratories are equipped withonly one meter per station. Beams [1] has shown that with external circuitry controlled by a PC, one can multiplexthe input and the output signals into a single voltmeter. He has cleverly designed a I-Q phase detector andincorporated it with his multiplexer to do both phase and amplitude measurement with only one digital multimeter.However, the frequency was limited by the phase detector to only two decades of dynamic range and to a maximumvalue of 100KHz.In our system we employ the digital oscilloscope of the set up rather than the multimeter (Figure 1). Unlike thedigital multimeter, the oscilloscope (1) provides multiple channels, thus eliminating the need for multiplexing, (2)has three orders of magnitude higher frequency bandwidth and covers DC through 100MHz, (3) displays actualwaveforms, showing distortions, noise and oscillations in real time without hiding or averaging them into thesignal's amplitude, and, (4) can be triggered externally for time delay (phase) measurements between the channels.In addition, from the waveforms displayed one can measure and verify the frequency of the signal. However,autoscaling of the time base and the vertical sensitivities of the channels and, extraction of amplitude, frequency andphase from the displayed waveforms become challenging difficulties. In the earlier generation of the system acompiled Quick Basic program was developed to control and step the signal generator, to autoscale the oscilloscopeand to measure and extract frequency, amplitude, phase delay data and to create a text file for use with a spreadsheetprogram. In the second generation of the system reported here National Instruments' LabView was employed tofacilitate a user friendly graphical interface, to create virtual instruments and plot the frequency response on thescreen while taking data. The "CIE-Bode" LabView program developed also creates data files that can be processedand plotted in Excel. The automated frequency response measurement system described has been used incharacterizing active/passive filter circuits and amplifiers designed in the junior electronics laboratory (Figures 2a &2b) and in the evaluation of the gain-bandwidth performance of student designed CMOS operational amplifierswhich were fabricated through MOSIS. The system was built and the programming was done as a part of seniorelectrical engineering capstone project at the University of XXX. In the presentation, principles of operation anddetails of the LabView programming will be given along with samples of various frequency response measurementsincluding MEMS (Micro-Electro-Mechanical-System) and piezoelectric resonators.[1] Beams, D.M., "Project TUNA - The Development of a LabView Virtual Instrument as a Class Project in aJunior-Level Electronics Course", Proc. of ASEE, s2259, 2000. [2] Walsh, S. and Orabi, I.I., "Application of LabView for Undergraduate Lab Experiments On VibrationsTesting", Proc. of ASEE, s2320, 2000. Figure 1. User Interface Window showing options for Signal and Oscilloscope settings Figures 2a & 2b. Bode Magnitude and Phase Plots of Freq Response Data from a MOSFET Amplifier tested ( A sample of student work done in Electronics Lab using the “CIE-Bode” setup)

Guvench, M. G., & Ye, M. (2015, June), Automated Bode-Magnitude and Bode-Phase Frequency Response Testing of Analog Systems and Electronic Circuits Using Standard USB-Interfaced Test Instruments Paper presented at 2015 ASEE Annual Conference & Exposition, Seattle, Washington. 10.18260/p.23610

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