Example of a First Order Temperature Instrument in a Practical Situation

Luis M. Vicente, Polytechnic University of Puerto Rico, Electrical and Computer Engineering and Computer Sciences
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Initial Publication Date: October 12, 2023

Summary

This is an example adapted from the textbook "Measurement and Instrumentation Principles from Alan S. Morris".
It shows the power of Matlab when working with Differential Equations, Laplace Transforms, and more, in a practical but not too difficult example for instrumentation engineers (Industrial, Mechánical, Manufacturing, among other).

This is the problem statement:
A balloon is outfitted with instruments that measure temperature and altitude, along with radio equipment to transmit these readings to the ground. Initially anchored, the balloon's instruments stabilize their output readings. The altitude instrument is approximately zero-order, while the temperature transducer is first-order with a 15-second time constant. The ground temperature (T0) is 10°C. The temperature (Tx) at an altitude of x meters is expressed as Tx = T0 - 0.01x, meaning the temperature drops by 0.01 degrees per meter.

Task:

Upon releasing the balloon, it ascends at 5 meters per second starting from time zero. Your task is to calculate the temperature readings measured by the instruments. Compare these readings with the actual temperature, analyze the differences, and draw conclusions from your analysis.

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Learning Goals

Students will learn practical problem when using First Order instruments, what is the physical meaning of time constant, visualize transient period and steady state period in a dynamical problem.
Matlab will help to visualize above concepts much better by showing graphs and similar.
Not too many thinking skills are needed to understand this problem.
The student is later on required to write a report on the whole problem to improve skills as writing, oral presentation, field techniques, equipment operation, among other.

Context for Use

Educational level: graduate course in Instrumentation.
Class size: any.
Institution type: University.
This is a classroom activity that can be finished in 40 minutes,
The student could not have too much experience with MATLAB since a step by step procedure is shown.
The students must know Ordinary Differential Equations and Laplace Transform principles.
This is a concept taught at the beginning of an Instrumentation course.

Description and Teaching Materials

The step by step description is located in one of the supporting materials: document named BalloonProject.pdf
The script file is located at mBalloonExercisev02.m
Exercise Step by Step instructions (Acrobat (PDF) 800kB Oct2 23)
Matlab script file of the Baloon Exercise (Matlab File 2kB Oct2 23)


Teaching Notes and Tips

Please read the pdf file for Exercise Step by Step instructions of the Balloon Exercise: BalloonProject.pdf
The Matlab script file is located at the file mBalloonExercisev02.m

Assessment

The assessment is for the students to repeat the experiment and hand in a report with all the steps and figures to show they learned the exercise.

References and Resources

This teaching activity was created as a part of the Teaching Computation with MATLAB Workshop held in 2023 at Carleton College.