A lighting system, a dimming control apparatus, and a dimming control method are provided. The sealing plate is constructed and arranged to isolate the wall segment from a volume inside the process chamber. The light device includes engagement extensions for selectively moving the light device to varying positions along the mounting panel for proper alignment and orientation of the light device. With this arrangement, even when a current flowing through the sensor is reduced, measured data is prevented from being buried in noise, allowing the sensor to operate on a small power and to measure a mechanical quantity with high precision even when it is supplied electricity through electromagnetic induction or microwaves.