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Crosscutting Laboratories For better Comprehension and Retention Steve Larson Lawrence Beaty HI TEC July 2014 Background • One of the challenges in the education of students about STEM concepts is developing methods to teach fundamental principles while keeping the value of those fundamentals relevant to students. • It is far too easy for the actual application and usefulness of technical theory to become isolated from application in such a way as to cause the student to “silo” the knowledge they have gained separately from its practical application. • When this occurs students are far more likely to rely upon rote memory rather than the mastery of concepts and use memorization and the following of procedures rather than critical thinking in solving problems. Why develop these Crosscutting Concepts? • Crosscutting concepts can help students better understand science and engineering practices. • Crosscutting concepts address multiple disciplines and consider the fundamental way things work. • They provide a platform to look at multiple applications for the same idea or concept. • Different crosscutting concepts align with both scientific and analytical thought The RTD Lab • The lessons developed provides practical and low cost platforms to integrate scientific application and classical STEM theory. One of the systems developed combines the very practical concept of measuring a temperature and transmitting that measurement value over a 4-20mA current loop with the application of several theoretical concepts such as an the bridge circuit, Thévenin's theorem, material properties of conductors, the principle of latent heat and several other electronic and physics concepts into a single exercise. The System A PT100 4-20 mA Transmitter produces a current relative to the temperature being measures. If measuring a temperature range between 200 degrees Fahrenheit and 400 degrees Fahrenheit the transmitter would produce 4 mA at 200 degrees and 20 mA at 400 degrees and should have a linear signal for all temperatures in between. A platinum resistance temperature detector (RTD) Pt100 is a device with a resistance of 100 Ω at 0°C .It changes resistance value as its temperature changes following a positive slope (resistance increases when temperature is increasing). RTD Calibration Procedure • Connect the current meter where labeled. • Connect the voltage meter across the 250Ω resistor. • Start the hot plate to boil the pan of water. (Use caution as the power supply is plugged into 120 volts). • Place the RTD Probe into the boiling water. • After a short period of time, at least 3 to 5 minutes. The current meter should read 20 mA (If not adjust the trim pots to achieve the desired 20 mA). Basic Procedure Continued • Place the RTD into a glass of ice water. • After a short period of time, at least 3 to 5 minutes. The Current meter should read 4mA (if not adjust the trim pots to achieve the desired 4 mA). • Place the RTD back into the boiling water to recalibrate if needed at 20 mA. • Place the RTD back into the Ice bath to recalibrate if needed at 4 mA . What are some additional ideas that can be taught from this lab? • • • • • • • • • • Ohm’s Law 4-20 mA process measurement Calibration Heat transfer concepts Thevenin’s principles Material Properties Current Loops Meter Loading Temperature Bridge Circuits Thanks You • Question? • Presentations, parts list and other information available at: www.isu.edu/estec
