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Six Rivers Charter School conductivity probe

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Revision as of 00:52, 22 December 2019 by Lonny (talk | Contributions) (removed instructions as instructed. Still needs an intro.)
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ENGR215 Project Page in Progress
This page is a project page in progress by students in Engr215. Please refrain from making edits unless you are a member of the project team, but feel free to make comments using the discussion tab. Check back for the finished version on 12/19/2019.

One of four Lighthouse Conductivity Meters constructed for Six Rivers Charter High School


Six Rivers Charter School has a conductivity probe that no longer works, is rusty, and a shock hazard if it is functional. Team Current Wave was tasked with developing a new qualitative data display that would guide students to understand the basic understanding conductivity through a liquid. Over the past semester, the team created a lighthouse probe to help not only facilitate learning with the student, but also to be engaging, aesthetically pleasing, and safe. The team was also asked to make replications that will help faciliate lab in groups of 4-5 instead of all the students sharing a single instrument.


The Current Wave Conductivity Probe is a device meant to provide educational value regarding the conductivity of various liquids for the students of Six Rivers Charter School. Team Current Wave will be working directly under Professor Morago, who not only is a professor in the HSU School of Education, but works as a teacher at Six Rivers Charter School.

Problem statement and criteria

The objective of this design project is to produce a conductivity probe for the use of Six Rivers Charter School in Arcata, CA. The chemistry department will use the probe to measure the conductivity of various liquids, as well as use the probe as a teaching mechanism for students. Therefore, it is essential to design a conductivity probe that is not only accurate, but that also facilitates learning for the students, can be handled by inexperienced users without easily breaking, and can provide easy usability. The goals and criteria for this design will be determined by the clientele at Six Rivers Charter School.

Table-1: Criteria and Constraints
Criteria Weight Constraints
Safety 10 Must not physically injure the user

(including shocks, cuts, etc)

Level of Engagement 9 Must be a visually pleasing display that captures the attention of the user/class
Ease of Repair 8 No more than a one page long repair sheet, no background knowledge required for repair
Durability 7 Lasts longer than 5 years

(other than replacement bulbs)

Cost 7 <$50 per probe
Feasibility 7 Simple enough to be built by undergraduate students within time constraints of the semester.
Educational Value 5 Must be able to teach students basic conductivity principles at a high school level
Aesthetic 4 Must be more visually appealing than last probe.
Inspirational Value 4 Must instill a curiosity in class that may lead students to having a higher level of interest in science.
A depiction of the major components of the Lighthouse

The Lighthouse Conductivity Meter is a probe used for measuring the conductivity of a liquid solution. The design consists of a wooden body with a 3D printed, PLA rooftop housing. Inside is a probe block that slides along a dowel to lower two probes into a solution. The probes are connected to an electrical circuit that lights a lightbulb at the top of The Lighthouse if the solution has a enough electrolytes to carry the current across the solution. The bulb increases in brightness with increasing conductivity.

Description of final project

The Lighthouse Conductivity Meter is a probe used for measuring the conductivity of a liquid solution. The design consists of a wooden body with a 3D printed, PLA rooftop housing. Inside is a probe block that slides along a dowel to lower two probes into a solution. The probes are connected to an electrical circuit that lights a lightbulb at the top of The Lighthouse if the solution has a enough electrolytes to carry the current across the solution. The bulb increases in brightness with increasing conductivity.

An image of all four of the completed Lighthouse Conductivity Probes

Operation and Maintenance

To operate the Lighthouse Conductivity Meter, first ensure that the galvanized nail electrodes are making metal contact with the probe block. Do this with the meter unplugged to avoid any small shocks. Next, plug in the meter, and place a solution in the base. Unscrew the wingnut on the side one full turn, and use the handle to lower the electrodes into solution. After observing any luminosity, raise the probe block back up and re-tighten the wingnut. Unplug the meter, and wipe down the electrodes to minimize rust build up.

Team Current Wave has uploaded an instructional video on how to use and maintain.


Prototype 1 was built out of cardboard to assess the shape and size of the body and look at options for dispersing light. After construction it was determined that the body was too small for a hand to place a beaker of solution within the body, and so dimensions were increased for the final model.
Prototype 2 was built out of plywood to assess the specifications and functionality of the probe body and probe slider components. After construction it was determined that the sliding components needed a low-friction surface to slide on. The final low-friction material chosen was a thin layer of felt.


Quantity Material Source Cost ($) Total ($)
2 Bolt Aces 0.65 1.42
4 Washer Ace 0.23 1.00
2 Nut Aces 0.25 0.54
1 Acrylic Knife Amazon 7.99 8.67
1 Acrylic Sheet Ace 14.99 16.39
1 Lightbulb Amazon 4.99 5.39
1 2.1 x 5.5 Wood Ace 1.50 1.61
1 Dowel Ace 3.99 4.29
1 Allthread rod Ace 2.89 0.20
1 Aluminum Sheet Metal Ace 8.99 9.79
1 Latching Tote Ace 11.99 12.99
1 1 W LED nightlight Ace 5.99 6.49
1 Socket Phen Ace 5.49 5.99
4 Bulk Fasteners Ace 0.50 2.20
Total Cost '

Testing Results

Team Current Wave conducted three unique material testing experiments to select the best possible canditates for probe metal type and light.The first two eperiments were a series of oxidation reduction reactions. In the first experiment, various metal washers were submerged un a conductive solution plugged into a 9V power source for 30 minutes. Due to the large surface area to volume ratio, all the metal anodes completely oxidzed with the exception of galvanized steel. This experiment was then replicated again with metal screws of various types because they have a better surface area to volume ratio, thus, oxidize at a slower rate. Furthermore, a voltmeter was attached to the electrodes to compare the voltage at the beginning to the end because oxidation generally lowers conductive capacity. Again, every anode experienced mass reduction and change in voltage capacity with the exception of galvanized steel. Thus, galvanized steel was chosen to be the probe material for the final design. Using the newly installed galvanized steel probes, we tested a series of lights in 4 different molar solutions to find an optimal lumnosity range for a quality qualitative display. Results revealed the most reactive bulb that survived all 4 solutions was the 3.8V 0.3A light bulb for the final design.

How to build

Building Process
Backpack frame bike trailer Step 1 : Make the initial plywood and plexiglas cuts
Sanding all plywood surfaces Step 2 : Sand all plywood surfaces
Assembly of plywood bodies Step 3 : Assemble bodies with the use of pre-drilled holes and wood screws
Allowing the glue to set in the probe block Step 4 : Assemble probe block -- drill holes for probes, PVC slider
Probe block wiring Step 5 : Assemble probe block hardware and fasten wiring between washer and stainless steel cutout
Laying out wooden components for coating of paint Step 6 : Disassemble components and prep for paint
Letting the wooden components dry Step 7 : Coat components in protective, water-resistant coating of paint
Reassembly after paint has been applied Step 8 : Reassemble components with the addition of wood glue at the joints
Lighthouse light fixture Step 9 : Apply the light socket, light bulb and the 3-D printed roof fixture to the top of the body


Introduce this maintenance section.

Maintenance on The Lighthouse is expected to be at a minimum. The bulb is expected to last at least 3-5 years, after which a replacement can be plugged into the housing. There are x extra bulbs for the probes, after which a pack of ten can be bought for $5.90. Corrosion is not anticipated to be an issue, particularly with the amount of usage that the probes will get per year. If any corrosion does take place on the probes over time, a new 16 penny galvanized nail can be inserted for the cost of about $.10 each. If the probes and the bulb were replaced at most every 3 years, the yearly cost of maintenance would be $.33. No other general maintenance costs are expected to be needed for The Lighthouse.


  • After each use unplug the conductivity probe and wipe down any solution with a towel.
  • When out of use, keep in a dark dry environment to avoid wear and oxidation.


This is only how to troubleshoot basic operation. For complex issues, contact Marco at

Problem Suggestion
Light does not turn on Unplug the power supply cord and gently twist the nails (that act as the probes) in a downward motion until the heads of the nails are fitting snugly against probe block. Plug the power supply cord back in. If issue continues, first make sure the other end of the power supply cord is plugged into a working wall outlet. If there are still issues, check the solution the electricity is going through, it may not be conductive enough. Lastly, if it still does not turn on, try using another lightbulb.
Probes corrode Bring the lever to the bottom of the lighthouse and pull push out the nails from the block. You can then replace them easily with new galvanized steel nails.

Discussion and next steps

The finished Lighthouses are sturdy, visually appealing product that will serve its purpose at Six Rivers Charter School. The Lighthouse provides a safer and more visually appealing product than what was previously used. Current Wave was pleased with the final product and are glad to have served the Arcata community. Current Wave hopes to inspires students to learn more about STEM related topics such as conductivity, oxidation and reduction reactions, and chemistry and engineering in general. The next steps for the lighthouses are for them to be painted by Six Rivers Charter School students.

Suggestions for future changes

Although the project hit all the necessary requirements for the project, there is always room for improvement. If this project were to be developed further, our team would find a more durable, cost effective, upcycled plastic substitute for the plywood body. Further more, the team would create a custom handle bent upwards for the slider so the dowel would not need to be secured at an angle for aesthetic purposes.


See Help:Footnotes for more.