A sensing apparatus (210) to measure ammonia in a gas mixture. The sensing apparatus (210) includes a sensing element, which includes substrate (218), a first electrode assembly, and a second electrode assembly. The first electrode assembly includes a first sensor electrode (212) coupled to the substrate. The first electrode assembly is configured to react to the ammonia in the gas mixture. The second electrode assembly includes a second sensor electrode (214) coupled to the substrate. The second electrode assembly is configured to react to the ammonia in the gas mixture. The first and second electrode assemblies are configured to generate a differential electrical signal in response to the ammonia detected by the second electrode assembly.
