Oceanographic Instrumentation, Measuring Temperature

Lauren Sahl, Karin Lemkau, Sarah O'Malley and David Avery, Corning School of Ocean Studies, Maine Maritime Academy

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Summary

Students open the "black box" of instrumentation by building a temperature sensor, modifying a computer program and collecting data to make a graph of the thermocline. Students will build simple electrical circuits, modify computer code for the Arduino microprocessor, and be introduced to sensor calibration. This activity is used to help students learn how the workhorse of oceanographic instrumentation, the CTD (conductivity, temperature, depth), works.

Context

Audience

This lab activity is placed in an introduction to oceanography course. The purpose of the activity is to demystify oceanographic instrumentation. It is too easy to view complex instruments and computers as black boxes. In this activity students see how these instruments are constructed and controlled. We have purposely made this activity simple enough that the instructor does not need background in electrical circuits or computer programming.

Skills and concepts that students must have mastered

Students should have familiarity with Excel. Other than this, since this activity is placed in an introductory course there are no previous requirements for skills and concepts.

How the activity is situated in the course

This lab can be a stand alone exercise although if you wish to have the students become more comfortable with Arduino and computer coding we suggest first doing an introduction to circuits and Arduino coding lab. We use this SERC activity, https://serc.carleton.edu/teachearth/activities/219496.html, in the lab session immediately preceding the activity presented here. In the lab session after completing the activity presented here students take a short oceanographic cruise and use a CTD to collect data. In that lab they create a data product similar to the one created in this activity. For instructors who do not have access to a vessel and a CTD, this lab could precede a lab where students work with CTD data.

Goals

Content/concepts goals for this activity

Expose the black box of a key piece of scientific instrumentation:
  • Students will build a working circuit and temperature sensor.
  • Students will be introduced to simple computer coding.

Calibrate an instrument:

  • Students will understand the need for, and process of, calibrating a temperature sensor.

Visualize data:

  • Students will use the power of a spreadsheet to visualize data.

Higher order thinking skills goals for this activity

Other skills goals for this activity

Description and Teaching Materials

For students there is some minimal pre-lab homework involving downloading necessary software onto computers. The exercise that takes place in lab can be carried out over multiple lab periods as necessary.

Workflow for instructors is outlined below:

Prior to Lab

1. Familiarize yourself with activity, kit components and functions. Instructor background (PowerPoint 2007 (.pptx) 6.8MB May22 19) This presentation is an instructor resource providing overview of the exercise and detailing kit components and their functions. A visual walk through of the circuit building portion of the activity can be found in the visual instructions presentation mentioned below (#9).

2. Assemble student kits. Instructors should package, as a kit, all of the pieces needed to build the electrical circuit. Arduino Circuit Materials list (Acrobat (PDF) 534kB May22 19)

The first time this will require some soldering of parts as the temperature sensors need to have jumper wires soldered onto the ends of each of the three wires. To do this you will need the following supplies:

  • Soldering iron
  • Solder
  • Male-male jumper wires (see materials list above for purchasing info)
    • 3 per two temperature sensors
    • Should be same color as temperature sensor wires
  • Wire stripper
  • Scissors/wire cutters
  • Electrical tape (or heat shrink and a heat gun)

The temperature sensors may come with the three wires exposed and stripped (if not, cut back some of the black covering on the temperature sensor to expose the three wires with their colored coverings and strip the end of the colored coverings off each of the wires). Cut three male jumper wires in half and strip the ends of the colored coverings. To each of the temperature sensor wires; twist on one of the jumper wires, solder the connection and insulate the soldered connection with electrical tape (or shrinkwrap). This movie illustrates the basics of the process. Temperature sensor preparation (MP4 Video 66MB Dec6 17)

The breadboard and Arduino board will also need to be mounted onto the Arduino/breadboard holder. Use the screws provided to mount the Arduino. Mount the breadboard by peeling off the backing to expose the sticky backing and pressing it into place. Make sure the boards are in the same orientation as shown in the visual instructions (# 9 below).

3. Have students download necessary software onto their computers. Students will need to download the Arduino IDE software and required libraries (both are linked in the Preparing Student Computers document below). We recommend that students download these when they have a fast internet connection. If internet speed is slow in the lab where this activity will be taught consider assigning the download as homework to be done prior to the exercise. Step-by-step instructions for preparing student computers can be found here. Preparing Student Computers.docx (Microsoft Word 2007 (.docx) 1.5MB Nov14 17)

4. Print student handouts. The student handout is self-explanatory. We suggest that students work in pairs. Student handout (Microsoft Word 2007 (.docx) 551kB Dec12 17)

5. Assemble supplies for lab. In lab students will be calibrating their sensor, testing the response time and making 2-layer systems to test their sensor. The various supplies for these steps are listed in the student handout (linked above) and have been compiled here for your convenience. Lab supplies list (Microsoft Word 2007 (.docx) 19kB May22 19)

6. Familiarize yourself with how to create a two layer system in a graduated cylinder by watching this video. Video on making a two layer system (MP4 Video 60.3MB Dec5 17)

7. Email link to the Arduino code to students for use in lab. This link takes one to the computer code required for this exercise. The link will need to be emailed to the students for use in class. It will open the Arduino code in an internet browser window. It can then be copied and pasted into the Arduino sketchbook and saved locally with the name acquire_temperatures. This email should be sent just before lab or after students are given a heads-up regarding the email and its purpose. https://d32ogoqmya1dw8.cloudfront.net/files/teachearth/activities/program_obtain_temperature_.txt.txt

In Lab

8. You will need all supplies previously assembled (#5). We provide one boiling water bath for the whole class. Alternatively, each group can be given a hot plate and beaker to make their own boiling water bath.

9. Visual instructions.Presentation designed to present to students during class. Contains step-by-step visual instructions for building the circuit. Visual Instructions for Arduino Circuit (PowerPoint 2007 (.pptx) 9.9MB Nov27 17)

10. Troubleshooting tips. Students may have some trouble uploading the program to the Arduino board, getting good temperature data or succeeding at the coding challenge. These tips walk you through solutions to these problems. Troubleshooting tips (Microsoft Word 2007 (.docx) 14kB Dec12 17)

Teaching Notes and Tips

If you are using the Introduction to circuits and Arduino activity as a precursor to this lab, you may need to modify or omit some of the hand outs (for example, students will not need to prepare their computers by installing the proper software more than once for these activities).

This activity uses Excel, and we find that our students are not very skilled in using this program. Some instruction in Excel basics will reduce frustration, and hopefully introduce students to the power of a spreadsheet. Although the student handout includes directions on making a scatter plot, and fitting a line to the data points be prepared to assist.

This activity is the first time students are asked to make a plot in the oceanographic convention, i.e. with depth increasing down. An example is included in the student handout. The instructor may also post one if desired.

Note, boiling water is the only notable potential safety concern. Take care not to drip water onto the electrical circuit.

Assessment

Whether students have met the objectives of this exercise can be determined by evaluation of the deliverables.

Deliverable One: Plot of calibration curve from Part C: Determining the accuracy of a sensor.

Objectives met: Use Excel to construct a calibration curve, use Excel to determine the temperature conversion formula.

Deliverable Two: Plot of the collected data in the oceanographic perspective, with thermocline labeled, from Part E: Time to take some data!

Objectives met: Collect, correct, plot and interpret the data, apply the temperature conversion formula to novel data.

Deliverable Three: Calculations and formula on student handout in Part C: Determining the accuracy of a sensor.

Objectives met: Understand how to use a calibration curve.

Deliverable Four: Optional screen shot from Part F: Coding challenge.

Objectives met: Analyze and modify a simple computer code.

Additional assessment options:

To reinforce and integrate the learning that occurs in lab into overall class content we suggest including material from this lab into exams or on lab quizzes. A link to sample questions is here. Example Assesment Questions (Microsoft Word 2007 (.docx) 319kB Dec5 17)

References and Resources

The Marine Advanced Technology Education Center (MATE at https://www.marinetech.org/home/ ) is a rich resource both for instructors and students. MATE offers workshops to teach instructors about marine technology. It sponsors remotely operated vehicle (ROV) competitions for students, and serves as a clearinghouse for marine related internships and jobs.

More information on the CTD (conductivity, temperature, depth instrument) can be found here: [https://web.archive.org/web/20181201134705/http://www.whoi.edu/page.do?pid=8415&tid=7342&cid=1003]

This link describes the thermocline in more detail, and links it to hurricanes: https://oceanservice.noaa.gov/facts/thermocline.html

A concise description of instrument errors and calibration is provided at https://learn.adafruit.com/calibrating-sensors/why-calibrate. This site has a different method for using the water bath data to calibrate the sensor. We prefer the method used in our exercise because it introduces students to another tool in Excel.

This SERC site also explains types of errors. https://serc.carleton.edu/quantskills/teaching_methods/und_uncertainty/measure_error.html

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