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A pH meter is an instrument designed to measure the hydrogen-ion level in water based solutions. A pH meter indicates the acidity and alkalinity and is sometimes also referred to as a potentiometric pH meter.

A pH meter works by measuring the voltage between two electrodes. The results are displayed by converting this information into a pH value.

The term 'pH' refers to a unit of measure with a range between zero and fourteen. The mathematical symbol 'p' represents potential, while the 'H' is the symbol for hydrogen.

### Applications

Harsh environments

Biological micro-environments

Laboratory experimentation

Quality control

Agriculture

Municipal water supplies

Brewing industry

Swimming pools

Food industry

Replacement parts are available, such as [pH electrodes](/web/c/test-measurement/liquid-analysis/ph-water-analysis-electrodes/) made from a special glass composed of alkali metal ions which sense the hydrogen ion concentration. As the electrode ages, the glass electrodes resistance changes.

pH meter calibration is required as electrodes run down eventually and need to be calibrated on a regular basis. Calibration in a pH buffer solution which has a constant pH value should always start with buffer 7.0 as this is point 'zero'. The pH scale has an equivalent mV scale from +420 mV to -420 mV. The buffer solution is available as a pre-mixed liquid or dry powder capsules.

### What types of meters are there?

**Pocket testers** are a device with an LCD display which can deliver fast and accurate readings. They are lightweight and easy to transport making them ideal for field use. Pocket tester meters are popular with students and researchers which they use for measurements in test tubes and vials. Features of a pocket tester meter include automatic buffer recognition, easily replaceable electrodes and thousands of hours of battery life.

**Portable pH meters** are handheld and lightweight. They contain Bluetooth technology which allows the information to be downloaded to a mobile or tablet. Multi-parameter meters are suited to robust industrial environments and have PC connectivity.

**Bench meters** are accurate, easy to use and available with Bluetooth technology and built-in printers. It is easy to transfer data via Bluetooth onto a mobile or tablet, or onto a PC via a USB cable.

**Test kits** measure the strength or weakness of a chemical presence by the degree of colour saturation. If pale then the concentration is low, if strong then the concentration is high. Adding the reagent to the compound allows the colour to be tested against a colour chart.



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pH Meters

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Hanna Instruments HI-9813-51 pH Meter 0.1pH Resolution +60 °C Max

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