Build and Test a Conductivity Probe with Arduino
Student groups construct simple conductivity probes and then integrate them into two different circuits to test the probe behavior in solutions of varying conductivity (salt water, sugar water, distilled water, tap water). The activity culminates with student-designed experiments that utilize the constructed probes. The focus is to introduce students to the fabrication of the probe and expose them to two different ways to integrate the probe to obtain qualitative and quantitative measurements, while considering the application and utility of a conductivity probe within an engineering context. A provided handout guides teams through the process: background reading and questions; probe fabrication including soldering; probe testing and data gathering (including circuit creation on breadboard); probe connection to Arduino (including circuit creation and code entry) and a second round of testing and data gathering; design and conduct their own lab experiments that use the probes; online electrolyte/nonelectrolyte reading, short video, comprehension check and analysis questions.
Students use an Arduino UNO, a breadboard and a LCD display to create a simple conductivity probe.Copyright 2015 Phillip Cook, Polytechnic Institute of NYU
Engineers often design sensors to fit their exact needs. Engineers planning solar panel installations require sensors that measure the amount of light falling on a given area. If engineers are dealing with aqueous or liquid solutions, it is quite common to characterize a solution's conductivity to gain insight into the types of solutes dissolved within the solution (either ionic or covalent solutes). Chemical engineers often create systems to transport fluids, so an understanding of fluid properties is important to the design process. In designing a desalination plant, engineers must be able to measure the amount of salt present in seawater and in the fresh water produced; a conductivity probe is a valuable instrument to identify the presence or absence of ionic compounds.
Through this lab, students are exposed to multiple ways that a conductivity probe can be used and challenged to consider its possible real-world applications. The primary function of the probe is to indicate the ease with which electrical current can flow through a solution; the easier current flows, the higher the conductivity. This single measurement determines whether an aqueous solution contains ionic or covalent solutes, an important first step in characterizing unknown solutions.
After this activity, students should be able to:
- Identify whether a solution is conductive.
- Construct a functional conductivity probe.
- Integrate a conductivity probe into a simple circuit.
- Utilize an Arduino with LCD display-to-display probe values.
- Determine the conductivity of an unknown solution.