A sensor device is formed from a metal film having a plurality of openings, a sensor material positioned within each of the openings, a light source that emits light having a first wavelength, and a light detector that detects light emitted from the light source and transmitted through or reflected from the openings. A tap assembly mounted on the upper-chamber upper wall has a riser tube projecting through the partition center part into a lower region of the lower chamber. A series arrangement of a second breakdown switch and a primary winding of a transformer is connected in parallel to said capacitor. A mounting plate covers the outside of the flange section.