Patent ID: 8909315

Claim:
A gastroscope comprising: an insertion tube having a size and shape allowing insertion of said insertion tube into the gastrointestinal tract of a subject, said insertion tube having a distal end; a sensor at said distal end of said insertion tube that is exposed to an interior of the gastrointestinal tract, 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; 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 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.