Salinity Sensor (for Groundwater)

This sensor measures the conductivity of water with a certain salt concentration. The higher the conductivity, the higher the salinity. Three lights indicate whether the conductivity is low, average, or high.

Arduino

Breadboard

2 electrodes

3 lights

1 resistance

wires

Power supply (e.g. laptop, batteries, powerbank)

3 cups

Demineralized water

Tapwater

Salt

Make a circuit with the Arduino and breadboard like the one in the picture:

- Connect two electrodes of choice, one to the 5V pin of the Arduino and one to ground. The wire going in ground needs a resistor.

- Add a wire from the groundwire to an analog pin in the Arduino.

- In another circuit, add three lights in parallel. Use pins according to preference and the ground pin.

Write a program in Arduino that measures the Voltage over the electrodes.

Make three voltage intervals with the values from the picture above. The lowest values turn on the first light, the middle values turn on the second light, the highest values turn on the third light.

Make sure you use Alternating Current, otherwise the resistance between the two electrodes keeps increasing which messes up your measurements.

Take three cups of water. Put demineralized water in the first one, put normal tap water in the second, and put a little salt (> 1000 mg/kg) in the third cup. Tap water already contains some salts.

When putting the electrodes in the different cups, different lights should light up.

Important to notice: make sure that the electrodes keep the same distance to each other when measuring (attach a strip or something between them) and keep the water temperature stable (best is around 25 degrees C).