Digital pH/ORP Meter for Water Testing

The pH meter and pH/ORP electrode selection

The pH/ORP meter diagram of ports definition

Communication

RS485 communication data and register address as follows:

PHM-PH160 pH Controller User Manual.pdf

Q1: What is the working principle of a pH meter?
A1: The pH meter works on the principle of a galvanic battery. The electromotive force between the two electrodes of the galvanic battery is based on Nernst's law, which is not only related to the properties of the electrodes, but also to the concentration of hydrogen ions in the solution. There is a the corresponding relationship between the electromotive force of the primary cell and the hydrogen ion concentration, and the negative logarithm of the hydrogen ion concentration is the pH value.

Q2: The same sample is measured on two pH meters at the same time, why are the readings inconsistent?
A2: Because the calibration conditions of the two pH meters are different (such as calibration done at different times), the measured values are different. Therefore, the pH meter should be calibrated at the same time with the same buffer, and then measured at the same time.

Q3: How do I know if the pH meter is accurate?
A3: Take three standard buffer solutions: pH 6.86, pH 4.00, pH 9.18 (preferably freshly prepared and at the same temperature), position calibration at pH 6.86, slope calibration at pH 4.00, and then test pH 9.18 to know the pH meter Is it accurate.

Tips: What is 1 point calibration of the pH meter?

Any kind of pH meter must be calibrated by pH standard solution before measuring the pH value of samples. For samples with measurement accuracy below  0.1pH, one point calibration method can be used to adjust the instrument, usually pH 6.86 or pH 7.00 standard buffer solution is used. Some instruments only have 0.2pH or 0.1pH, so the instrument only has a positioning adjustment twist, the specific operation steps are as follows.

• Measure the temperature of the standard buffer solution, check the table to determine the pH value at that temperature, and adjust the temperature-tasting knob to that temperature.
• Rinse the electrode with pure water and shake it dry.
• Immerse the electrode in the buffer solution and shake it to rest. After the reading is stable, adjust the positioning knob to make the instrument display the pH value of the standard solution.
• Remove the electrode, rinse and shake dry.
• Measure the temperature of the sample and adjust the temperature compensation knob of the pH meter to that temperature value.
• Immerse the electrode into the sample solution, shake it and leave it at rest, then read the value when the display is stable

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