It can be expensive and time consuming to replace inductive sensors because users must change out both the sensor and amplifier.
To solve this problem, engineers at Turck, a German firm with U.S. headquarters in Plymouth, Minn. (turck.com), developed the CQ40 and CQ80 inductive presence sensors. The sensing head detects metal objects and can be detached and replaced if it fails. The CQ40 detects objects up to 25 mm away. (Specs for the CQ80 are not yet available.) The sensor head works despite temperatures to 250°C, making the sensors well suited for service in drying and curing ovens for automotive painting systems. The standard eurofast M12 connectors also use Teflon cables with aluminum sleeves, so they won't contaminate painting systems.