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Revisiting Electrical Circuit Labs

As more courses are being taken online and in distant learning environments, many laboratory focused classes are left behind due to the inability to provide an adequate lab experience. This can be especially true for one of the most fundamental electrical engineering courses, Electrical Circuits. The irony is that most modern laboratory equipment actually rely upon the concepts taught in this class. This paper will outline a sequence of labs that will step students through the design and construction of their own lab equipment. Starting with the introduction of voltage and current dividers that enable students to scale common battery packs to the desired voltage levels. Students are then stepped through the use of an inexpensive panel meter, to design a simple multimeter. It is recommend that this is done early enough in the semester, so that motivated students can layout, populate, and test a custom printed circuit board. The battery packs and the student designed multimeter are adequate to study all DC circuits, including Operational Amplifiers. After the introduction of Op Amps, buffering can be added to the multimeter to improving its functionality and decreasing any loading effect. The minimal shunt capacitance in the multimeter circuit also allows it to be applied to RC and RL transient circuit analysis, so long as time constants are kept on the order of seconds. After transient circuits, student are shown how to use positive feedback Op Amps to create a multivibrators, in lieu of the classical 555 chip set. Additional Op Amps can be used to provide signal shaping into square, triangle, and sawtooth waveforms. A low Q tank circuit can also provide sinusoidal signals by filtering out harmonics from the triangle waveform. Low frequency DC biased AC small signal analysis can be performed using the student designed multimeter, or a National Instruments myDAQ or similar device which could be required in lieu of a textbook, as more open source resources become available. By the completion of this course sequence, students will have covered all of the fundamental measurement techniques and learned how to incorporate these simple circuits into more advanced systems. The only drawback to this method is that student will not gain familiarity with specific brands of high end test equipment. But that familiarly should be obtainable by reading the technical manual or by completing one or two quick tutorials on the specific device, since all of the fundamentals will have been introduced.