Getting Started with Gravity: Analog Spear Tip pH Sensor Kit

This guide covers the assembly of the spear tip shield and calibration of a pH probe, emphasizing accurate measurement techniques and the importance of using standard solutions and a stable power supply.

Spear Tip Shield Assembly

Before measuring the semisolid material, the included stainless steel spear tip shield should be installed first to protect the glass probe.

If you want to immerse the pH probe into the buffer solution to calibrate it, you could install the spear tip shield after finishing calibration.

unscrew the protective solution bottle and pull out the top cap with rubber pad from the probe.
unscrew the fixed ring and carefully insert the spear tip shield to the probe. Finally, screw the fixed ring back to the probe to hold the shield.

The following diagram below shows how to install the spear tip shield to the probe step by step.

Spear_Tip_Shield_Assembly

Probe Calibration

Caution

Please use an external power supply for more accuracy voltage. The closer your power supply can maintain a steady 5.00V the higher pH accuracy readings are.
It is recommended to calibrate the probe with the standard solution before each use to obtain more accurate results. The best calibration temperature is about 25 ℃.
It is necessary to use pure water to clean the probe before measuring another solution to prevent solution contamination. Cleaning with distilled water is recommended.
After 2 hours of continuous use, the probe should be calibrated again to ensure the accuracy.
Please keep the signal transmitter board clean and dry to avoid affecting the input resistance of the BNC connector.

Calibration Step

If this product is used for the first time, or if it has been used for a while, calibration is needed to reduce the error. During calibration, if bubbles in the glass bulb of the electrode head were found, you could slightly thrown off the probe several times to make the bubbles disappear.

Put the pH probe into the 7.00 standard buffer solution and wait for one minute. Open the serial monitor of the Arduino IDE, then the pH value will be printed on it. The error should be less than 0.3. Record the printed value and compare it with 7.00. The difference should be input into the "Offset" variable in the sample code. For example, the printed value is 6.88, so the difference is 0.12. The "# define Offset 0.00" should be changed to "# define Offset 0.12" in your code. Then upload the new code.
Clean the pH probe with pure water. Distilled Water is recommended. Then absorb the residual water traces with filter paper. Put the pH probe into the 4.00 pH standard solution. Then wait for at least one minute. Then open the serial monitor of the Arduino IDE and adjust the potentiometer on the transmitter board to tune the gain until the printed value is stable at around 4.00.
Clean the pH probe with pure water. Distilled Water is recommended. Then absorb the residual water with filter paper. After the above steps have been completed, the calibration is complete. Then the pH electrode can be used for the actual measurement.