Multi-film resistive gas sensor and system

A sensor, comprising:

• an element section,
• the element section including
• a base including a first region, a second region and a third region,
• a first element fixed to the first region,
• a second element fixed to the second region, and
• a third element fixed to the third region,
• the first element including
• a first fixed portion fixed to the first region, and
• a first film portion supported by the first fixed portion,
• the first film portion including a first resistance member and a first layer including a first material,
• the second element including
• a second fixed portion fixed to the second region, and
• a second film portion supported by the second fixed portion,
• the second film portion including a second resistance member,
• the third element including
• a third fixed portion fixed to the third region, and
• a third film portion supported by the third fixed portion,
• the third film portion including a third resistance member,
• the second film portion and the third film portion satisfying at least one of a first condition or a second condition,
• in the first condition, the second film portion and the third film portion not including the first layer,
• in the second condition, the second film portion including a second layer, a second material of the second layer being different from the first material, and
• in the second condition, the third film portion including a third layer, a third material of the third layer being same as the second material.