Capacitive Proximity against Inductive Where the Target Material Changes
Metallic target variation demands Factor 1 inductive sensors to eliminate reduction factors, while polymer and liquid swaps require capacitive heads with active guarding.
Inductive Proximity
Sensing Method
Non-contact detection of metallic objects relies on the creation and monitoring of alternating electromagnetic fields. The technique of inductive proximity uses an internal oscillator and a coil to project a high-frequency magnetic field from the active face of the sensor. When a conductive object enters this field, it absorbs energy through the generation of eddy currents, which reduces the oscillation amplitude.
This drop in amplitude is detected by a trigger circuit that changes the output state of the device.
Target Interaction
Ferrous metals containing iron produce a much stronger response than non-ferrous metals like aluminum or copper. For this reason, inductive proximity sensors must be calibrated with correction factors when detecting non-magnetic metals. These correction factors vary from zero point three to zero point eight times the nominal sensing distance.
Range Limitation
The strength of the projected magnetic field decays rapidly with distance from the sensor face. Consequently, inductive proximity systems are restricted to short-range tasks, with typical operating distances ranging from one millimeter to twenty millimeters.
Industrial Application
Because these systems do not use optical or mechanical contact, they are highly resistant to dirt, dust, and oil accumulation. This makes them suitable for harsh manufacturing environments where other sensor types would fail due to contamination.