The pH metry is the method of choice for the study of gastroesophageal reflux (heartburn, acidity). It consists of the installation of sensors in the esophagus that measure the acidity coming from the stomach in a period of 24 to 48 hours.

The most widely used systems for pH metry are the bravo wireless system and impedance pH. The latter has the advantage that it not only measures acidity, it also determines alkalinity and gas, which are factors that also cause symptoms.