MJ-WQS-pH pH Sensor

MJ-WQS-pH is a simple yet reliable pH sensor for water quality monitoring

Designed to be easily integrated into a system, it comes with an RS485 Modbus protocol.

Built with IP68 housing, it is suitable for long term deployment underwater.

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MJ-WQS-pH is a digital output water pH sensor developed and manufactured by MJ Instruments. With sensor body filled internally which acts as sensor weights as well as protecting the electronic components, the sensor is well suited for long-term deployment. The body is built with corrosive resistant material, allowing it to be deployed at industrial discharge for pollution monitoring. Different housing is also available upon request. With standard RS485 Modbus output, it is easy to integrate the sensor into the commercial controllers.

Contact us today for your water monitoring solution.

pH (Wiki)

In chemistry, pH (denoting ‘potential of hydrogen’ or ‘power of hydrogen’) is a scale used to specify the acidity or basicity of an aqueous solution. Lower pH values correspond to solutions which are more acidic in nature, while higher values correspond to solutions which are more basic or alkaline. At room temperature (25 °C or 77 °F), pure water is neutral (neither acidic nor basic) and has a pH of 7.

The pH scale is logarithmic and inversely indicates the concentration of hydrogen ions in the solution (a lower pH indicates a higher concentration of hydrogen ions). This is because the formula used to calculate pH approximates the negative of the base 10 logarithms of the molar concentration[a] of hydrogen ions in the solution. More precisely, pH is the negative of the base 10 logarithms of the activity of the hydrogen ion.

At 25 °C, solutions with a pH less than 7 are acidic, and solutions with a pH greater than 7 are basic. The neutral value of the pH depends on the temperature, being lower than 7 if the temperature increases. The pH value can be less than 0 for very strong acids or greater than 14 for very strong bases.

The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. The pH of aqueous solutions can be measured with a glass electrode and a pH meter, or a colour-changing indicator. Measurements of pH are important in chemistry, agronomy, medicine, water treatment, and many other applications.


pH Range

0 – 14

pH Accuracy


pH Resolution


Temperature Range

0 – 50 Deg C

Temperature Accuracy

+- 0.2

Temperature Resolution


Max Pressure

50 Psig

Reference Solution

Ag/AgCl Double Salt Bridge


RS485 Modbus

Protection Rating


Power Supply

DC 12V