An online pH indicator is a real-time monitoring device used to continuously measure and display the pH level of a solution or fluid within a system. It features a digital display that provides instantaneous pH readings, often with high precision, and may include calibration options for accuracy. Designed for integration into various processes, the indicator typically includes a pH sensor or probe that is installed directly into the fluid stream. Advanced models may offer additional functionalities such as temperature compensation, data logging, and alarm settings for out-of-range pH levels. Online pH indicators are essential for maintaining optimal conditions in industrial, environmental, and laboratory settings.