Patent ID: 8918154

Claim:
An endoscopic capsule comprising: a biocompatible capsule housing having a size and shape for movement through the gastrointestinal tract of a subject; a sensor apparatus inside said housing that detects medical information; a sensor located at an exterior of said housing, that is exposed to an interior of the gastrointestinal tract, and communicating with said sensor apparatus, said sensor comprising a first electrode made of a noble metal, which cannot be attacked by acid; and a second electrode made of silver with a silver chloride layer that is exposed to said interior; said sensor apparatus comprising a voltage source connected between said first electrode and said second electrode that produces an electric voltage between said first electrode and said second electrode with said first electrode operated as a reference electrode and said second electrode operated as a measurement electrode; and said sensor apparatus comprising a detector that detects a change in an electrical variable between said first electrode and said second electrode when ammonia is present in said interior between said first electrode and said second electrode, by said silver chloride layer participating in a chemical reaction with said ammonia.