When ESCHA Bauelemente GmbH, a connectivity manufacturer in Germany, decided to seek out a more reliable solution for position sensing on its injection molding machines, the company found itself with limited product options. The potentiometric sensors it was using to detect the position of locking devices and ejectors were not robust enough to withstand moisture in the environment, which resulted in a lot of maintenance work for ESCHA engineers. Other measuring principles, like magnetostrictive devices, were too costly to implement. The introduction of a linear inductive (LI) sensor that used cutting-edge sensing techniques by TURCK Inc. provided new options for ESCHA, and the manufacturer chose to cooperate with TURCK in a pilot project to replace four of its potentiometric sensors with the first series of TURCK LI sensors.
The result was an accurate sensing solution that resisted moisture ingress and came with an attractive price tag. “One of the most significant advantages of TURCK's LI sensors is their rugged housing that makes them insusceptible to moisture,” says Markus Hühn, head of the connector production department with ESCHA Bauelemente GmbH in Halver. A fully sealed aluminum housing protects the LI sensors from dirt and moisture. “The contact-free inductive resonant principle works absolutely maintenance-free. TURCK's sensors have been meeting our expectations completely.”
Another aspect that sets LI sensors apart from other sensing techniques is the absence of magnets in its design. Magnetostrictive and conventional inductive position sensors use magnets in their design that can experience electromagnetic interference in industrial environments. The LI sensor does not use magnets, but rather it detects an object's position via a resonant positioning device. An emitter/receiver coil system generates a high-frequency alternating magnetic field that activates the resonator integrated into the positioning device. Each time the transmitting coil stops transmitting, the resonator induces voltage into two receiving coils integrated into the sensor. The voltage intensity depends on where the positioning device overlaps the receiving coils. An integrated 16-bit processor provides a corresponding proportional output signal in different formats: 0 to 10V, 4 to 20 mA, I/O-Link or SSI. Although there are several options for position detection — ranging from analog sensors, to incremental devices, to digital switches — virtually none of these can be easily applied to both short-range and long-range applications. Due to their electronic design, TURCK's LI sensors provide measuring ranges between 100 and 1,000 mm. Using only one sensor family to cover these measuring ranges simplifies warehousing and helps users reduce their total cost of ownership.