pH determines the acid and base characteristics of water. A pH of 7.0 is neutral; values below 7 are acidic and values above 7 are alkaline. Excessively high or low pH levels are often associated with nutrient deficiencies, metal toxicities, or other problems for aquatic life. High pH makes ammonia more toxic. During algal blooms, photosynthesis increases the water pH, especially in stagnant or slow-moving water.

pH is measured by a sensing electrode for Hydrogen and a reference electrode along with a meter to measure the electrode potential. The YSI pH sensor is a glass bulb filled with a solution of stable pH (usually 7), so the inside of the glass surface experiences constant binding of H+ ions. The outside of the bulb is exposed to a water sample where H+ varies. The resulting differential of H+ creates a potential which is read by the meter versus the stable potential of the reference electrode.

A Practical Guide to pH Measurement - The YSI pH Handbook

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pH Resources

Laboratory pH Electrode Calibration Guide  pH Download Now Button
Laboratory pH Electrode Application Guide  pH Download Now Button
Laboratory pH Electrode Selection Guide  pH Download Now Button


YSI pH LogoEssential pH Posts on the Blog

pH Measurement Methods - Advantages and Disadvantages

pH Meter Calibration Problems? Check Out These 12 Tips!

Why is the pH Scale Logarithmic?

Anatomy of a pH Electrode | Glass pH Probes, Part 1 of 4

Extend the Life of Your pH Electrode in 3 Practical Steps

pH in Water - YSI knows pH

pH measurement in water.

Featured pH Products

TruLab pH/ISE 1320

Dual channel benchtop pH/ORP/ISE instrument


TruLab pH 1110

pH/mV single channel benchtop instrument with BNC and two banana plug connectors


EcoSense pH100A Meter

pH, mV, Temp Instrument Only


Pro10 pH or ORP Instrument

pH or mV (ORP) and Temperature Handheld Instrument. Meter Only.


MultiLab 4010-2

Two channel benchtop multiparameter instrument


IoLine - 3 in 1

IoLine - 3 in 1 Electrode


EcoSense pH10A Pen Tester

pH Temperature Pen Tester


MultiLab IDS 4110-3 pH and Temperature Sensor

Combination pH and temperature, Plastic, Gel filled, digital, double junction probe, 3 meter cable


Pro1020 Dissolved Oxygen and pH or ORP Instrument

Dissolved Oxygen, pH/mV and Temperature Handheld Instrument. Meter Only.


MultiLab IDS Kit

Laboratory instrument for pH, ORP, conductivity and BOD in any combination.

$1,320.00 - $3,000.00