Our electroconductivity sensor was designed as a simple way to measure the amounts of dissolved substances in different water samples. It can also be used as a (short-term) soil moisture sensor!
This sensor is made of two wires separated by an air gap. The air gap allows us to test how well a material or substance conducts electricity.
Full build instructions for this sensor can be found here, and a custom workbook for this sensor created by the Microsoft HackingSTEM team can be downloaded here (please note this is a link to a download).
For educators, we have two full lesson plans:
1. Measuring Water Quality to Understand Human Impact
2. How are Ocean Currents Formed?
Build an Electroconductivity Meter
Mark your straw at 14 cm. Cut at your mark.
Next, mark both of your coffee stir sticks at 13 cm and make cuts.
Using your hot glue gun, run a thin line of glue along the length of one of your stir sticks.
Quickly press the sticks together until the glue has cooled.
Measure and cut two lengths of 17 cm stainless steel wire. Straighten out the wires the best you can.
Place the wire on the stir stick so that it is centered and the ends extend about 1.75 cm beyond the stir stick.
Center your other wire opposite the first. Tape the wires onto the stir sticks.
Tape the middle and opposite ends of the sticks to hold the wire in place keeping the wires centered on the sticks.
Push the stir sticks with wire into your 14 cm straw.
Measure to make sure your wires stick out of the end of the straw at the 1.5 cm mark.
Dab some hot glue inside both ends of the straw.
Measure and cut your other length of straw at 4 cm
Cut the 4cm straw in half, then dab some hot glue on the end and...
... attach to the end of the straw! This will act as a shield guard for the sensor wire ends.
Bend the longer ends of the wire as shown in the photo above. This gives the alligator clips a better connection once attached.
Attach alligator clips to the bent wires. Awesome! You’ve completed the EC sensor. You care now ready to connect to your microcontroller.
Connect your alligator clips to the Arduino Uno as shown in the Attachments section.
If you are comfortable writing Arduino code, use the analog input pins to measure the voltage changes across the EC sensor. You are also welcome to use our sketch which is provided in the Attachments section.
We love when folks use and hack our projects! Share your creations with us on your favorite social media channel, or let us know if you have any questions!