Testing the Inductive Sensor on glass
The glass plate is 4.9 mm thick, and remember the sensor is rated for 8 mm proximity distance. Here you can clearly see the red LED light is off which means the sensor has failed to detect the aluminum 4.9 mm below the glass plate - not good. OK, I removed the glass and slowly lowered the sensor down towards the aluminum, it triggered at 4.5 mm above the aluminum - this is not what I want.
Alright recall that an Inductive sensor uses magnetic field to detect metal and aluminum does not react well to magnet, I decided to use my caliper which has a thin layer of stainless steel.