A two semester, multi-approach instrumentation project for mechanical engineering students

As part of a third-year mechanical engineering instrumentation course, students are challenged to design, fabricate, test, and characterize a custom air speed measurement instrument. The same instrument is then used, and enhanced, by the same students in their senior year in a microcomputer interfacing course. The enhanced instrument is then retested and characterized. The enhancements are evaluated by the students for their merits and improvement in overall instrument functionality. Specifically, the students design a Pitot-static probe to comply with loose specifications for size, weight, and materials. An electronic gauge pressure transducer with analog voltage output is used as the measurement device. The third-year students test the performance of and develop a calibration curve for their designs in a wind tunnel. The students also write a specification for their instrument such that it could be commercially produced. As seniors, the same student teams enhance their instrument's design by including an embedded microcontroller. The microcontroller includes analog-to-digital converter and serial port peripherals. The students develop microcontroller firmware to perform measurements of the pressure transducer output voltage, apply the calibration curve information, and transmit the airspeed to an external computer via a serial data line. By using the same instrument for both courses, the students get to experience the tradeoffs associated with different approaches to the same problem. This paper presents the projects and the tradeoffs encountered by the students as each design approach is implemented. Design team dynamics due to the time span between courses is also presented and discussed.