A Freshman Module To Teach Instrumentation Methods

Evolution of modern electronic devices has reached a level where a black-box approach to designing and building systems is within the capabilities of beginning laboratory experiments. This facilitates the introduction of modern instrumentation methods to freshmen in an engineering curriculum. The paper describes a freshmen module designed to provide an exposure to transducers, signal conditioning, computer interfacing and signal processing. The module consists of a coordinated set of lectures and laboratory experiments. The lectures begin with the concept of a transducer using the strain gage as a basic transducer. Introducing a differential amplifier using an op-amp as a basis follows this. Block diagram concepts are used throughout. In the first laboratory of the module, a cantilever with two strain gages connected to a differential (instrumentation) amplifier are used to measure loads and deflections. The output of the differential amplifier is read using a meter. Students build the circuits, calibrate them with known weights and then use them to measure an unknown weight and deflection. The second part of the module introduces concepts of inputting signals into a computer, with the analog-to-digital converter being described as a functional block. In the laboratory, students connect the output of the differential amplifier to a commercial analog-to-digital converter unit and acquire data into the computer. Using a narrowband digital filter to process the acquired data, students determine the natural frequency of the cantilever with applied weight loads.