pH Sensor

Introduction

This page describes how to set up and use a pH sensor.

Materials

The kit includes the following items:

  • pH probe
  • pH controller board (MinipH by Sparky's Widgets)
  • laser-cut base plate
  • screws and rubber feet

Assemble pH Board

  1. Attach the pH controller board to the laser-cut base plate using the provided screws:
  2. Attach the rubber feet to the bottom of the base plate:
  3. Connect the probe to the controller board:
  4. Connect the pH controller to your Arduino using one of the I2C plugs.
  5. When you are ready to use the probe, unscrew the storage container that is attached to the end of the probe. Be sure not to spill any of the storage liquid.

Using the Kit

The pH sensor can be used with the Exploring pH lesson.

You can also use the Sensor Plotter (select the MinipH device type).

After each use, dip the probe into distilled water for cleaning, then place the probe back into the storage container with the storage liquid.

Calibration

You'll need a two buffer solutions. One with a pH of 7 and one with a pH of 4.

  1. Load the pH Calibration sketch on your microcontroller.
  2. Rinse your probe with distilled or deionized water.
  3. Dry the probe, especially the tip, with a clean paper towel.
  4. Place the probe in one of the buffer solutions. Only the tip of the probe needs to be submerged.
  5. When the value stabilizes, make a note of the value and which buffer solution the value is for.
  6. Rinse and dry the probe again.
  7. Place the probe in the other buffer solution and note it's value as you did before.
  8. Click on the Code tab for the pH Calibration sketch.

  9. At the top of the sketch, replace the values for PH_7_VALUE and PH_4_VALUE with the values you noted earlier.

    #define PH_7_VALUE <your-value-here>
#define PH_4_VALUE <your-value-here>

  10. Send the sketch to your Arduino with the modified values.

  11. Check the buffer solutions again and verify the calibrated value. Make sure you rinse and dry the probe after each reading.

Other sketches that use the pH Sensor will have similar sections where you can place your own calibration values. The pH sensor will drift over time and will need to be recalibrated. Just follow this procedure whenever you need to recalibrate.

Troubleshooting

If you have any trouble, email support@manylabs.org.

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