25 Jul 2024


`Printed` inductive sensors have a core advantage

`Printed` inductive sensors have a core advantage

Turck Banner has developed a new inductive sensing technology which eliminates conventional ferrite cores and wound coils, by using coils that are “printed” onto a circuit board. Advantages claimed for the new technology include: switching distances that are up to 2.5 times longer than normal; the ability to sense almost any metal; fast switching speeds; immunity from the effects of EMC and magnetic fields; and the ability to recess the sensors easily to protect them.

The Uprox+ sensors (above) are an evolution of the original Uprox sensors that Turck launched in 1992 and are now said to hold 6% of the global market for induction sensors. The new generation, developed in conjunction with Ford, are so flexible that the number of sensors needed for different applications can be reduced dramatically. Ford, which is standardising on the new sensors in its European plants, reckons that just 12 of the new sensors will replace 400 previous devices.

The PCBs at the heart of the new sensors contain a pair of printed emitter coils that induce magnetic fields, and a pair of receiver coils that sense changes in these fields caused by metallic targets. The emitted signals are said to be four to five times more powerful that those from traditional ferrite coils. A custom chip evaluates the signals from the receiver coils and provides temperature compensation.

Unlike traditional inductive sensors, no reduction factors need to be applied when sensing different materials, such as iron, copper, brass, stainless steel, or aluminium. The sensors` fast switching speed makes them suitable for applications such as measuring rotational speeds.

Because there are no ferrite coils, the sensors are not susceptible to electromagnetic interference. They have been designed to comply with EN 61000-4-6, which comes into force next year. They are protected to IP68.

About 30% of all sensor failures are the result of mechanical damage. To minimise this risk, the Uprox+ sensors can be recess-mounted, with a much smaller metal-free zone than would be needed for conventional ferrite-based sensors.

Turck says that the ability to standardise on a few sensors bought in large volumes, and the elimination of many costly “specials”, will cut costs for most users. Ford estimates that the new devices will cut its inductive sensing costs by 15-30%.