Task
Non-ferrous Metal Switches detect only non-ferrous metals such as aluminium and brass. They attain the same switching distances as Inductive Proximity Switches of the same size. Non-ferrous Metal Switches cannot detect materials that contain iron, which makes this type of proximity switch especially suitable for distinguishing between ferrous and non-ferrous metals.
Mode of operation
A frequency and amplitude stabilised oscillator O supplies an AC bridge circuit B. The oscillating circuit S, consisting of a coil contained in a channel-shaped ferritic core and a capacitor, forms one branch of the bridge. The output stage A amplifies the voltage of the bridge and a comparator converts it into a switching signal. This low resistance switching signal is available at the output of the amplifier stage V.