A pH meter, also called a sensor or tester, is a device used to measure the acidity or alkalinity of a substance. A pH meter is either portable, or has a benchtop body. Many portable meters are handheld devices. Some testers have an internal sensor, and may have a tip and body that fit inside of a container for measurement. A meter is commonly used in many different environments from laboratories to field research and manufacturing facilities. Researchers, manufacturers, and hobbyists use a pH meter in aquaculture, agriculture, wine-making, and water-testing, and for scientific applications. Some pH meters may measure additional parameters such as dissolved oxygen (DO), conductivity (also called electro-conductivity or EC), temperature, total dissolved solids (TDS), salinity, resistivity, or oxygen reduction potential (ORP)/mV.

LaMotte manufactures analytical reagents, portable water testing instrumentation, and microbiological testing products. The company, founded in 1919, is headquartered in Chestertown, MD.