Chips can also stick to and embed themselves in the sensor face, degrading detection capabilities. A ferrous-only proximity switch from ifm efector inc., Exton, Pa., uses a one-piece housing, so aluminum chips do not interfere with sensing. And its multicoil sensor detects only steel and other ferrous metals, so the switch ignores aluminum chips that cause false triggers. The switch is compatible with the oils and coolants used in machining and has a zero-leak, IP68 protection rating. The 12-mm-diameter switch has a 3-mm flush-mount sending range, while the 18-mm-diameter switch has 5-mm range.