The power of Hydrogen in any liquid can be measured with a total pH scale range of 0-14 where 7.0 is considered as a neutral value. The pH electrode has a single cylinder that allows direct connection to the input terminal of a pH meter, controller, or any pH device which has a BNC input terminal.
You can just connect the pH sensor with a BNC connector, and plug the PH2.0 interface into any analog input on the Arduino controller to read pH value easily but you have to calibrate it before use if the pH probe was kept long. Calibration can be done via software or using a potentiometer present on the device.
|Heating Voltage||5V ± 0.2V DC/AC|
|Detection concentration range||PH0-14|
|Detection range of temperature||0-80°C|
|Working Humidity||95% RH|
|Service life||3 years|
|Output||Analog voltage signal|
|DO||3.3V pH limit trigger|
|PO||pH analog output|
|GND||GND for pH probe|
|GND||GND for board|
|POT1||Analog reading offset(Nearest to BNC connector)|
|POT2||pH limit setting|
As we can observe that in the circuit there are two knobs. One which is near the BNC connector probe is the one that regulates the offset, the other is the limit of pH.
- Offset: the mean (range) of the probe oscillates between negative and positive values. The 0 represents a pH of 7.0.since we are not reading from the electrode directly but from the voltage adapter, it has converted the original voltage (-5V ~ +5V) to Arduino compatible voltage, i.e. 0 ~ 5V
- Limit of pH: This knob is for setting a limit value of the circuit for the pH sensor that makes the LED red turn on and the signal of pin Do is put on ON.
In addition, we need to calculate the conversion of the voltage that will give us the pH sensor to what we will need two reference values of pH and measuring the voltage returned by the sensor on the pin Po. It is better to use a solution for calibration. These solutions are sold in different values, although the most common are pH 4.01, pH 6.86, and pH 9.18.
Using the envelopes with pH 4.01 and pH 6.86 we obtain the voltages on the pin Po 3.04 V and 2.54 V, respectively. The sensor is linear so that by taking two points, we can deduce the equation to convert the measured voltage to pH. The formula overall would be y=mx+b, so we have to calculate m and b as x would be the voltage e and the pH. The result is y=-5.70 x+21.34.
Connection with Arduino
To connect it with Arduino, you will need an analog input (A0), power (5V), and two GND that in reality in the sensor circuit are separated but we can use the same.