Bezel and front cover with set point knobs and zero adjustment screw removed to expose Photohelic switch gage set point mechanism. Cover is clear polycarbonate plastic.
Gage pointer and light shutter are mounted on helix and balancing counterweight. Shutter passes through slot in optical limit switch to expose phototransistors to integral infrared light source or mask them depending on applied pressure.
Light shield effectively protects phototransistors from strong outside light sources yet allows free pointer movement. It also gives interior a clean finished look.
Optical limit switches are used for reliability and long service life. Attached directly to set pointers, they are individually aligned to assure precise switching accuracy.
Semi Flexible drive shaft connects to set point knobs.