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turck40413cover story

Hannover Messe Hall 9, Stand H55

The encoder world is divided. On one side are the proponents of optical and potentiometric encoder, on the other followers of magnetic systems. Has recently Turck the world's first inductive encoder selected the golden mean. The advantages of the previous solutions were combined, eliminating the disadvantages. The result is the complete contact and therefore absolutely wear-free inductive encoders RI360P-QR24. This provides the user with the only type of encoder is available, which is permanently sealed and therefore not eventually end up as electronic waste.



Optical encoders: preprogrammed large space

turck10413Optical encoders are as absolute or incremental encoders widespread. They capture angle or rotational movements, by transferring the rotational movement of a shaft on an optically encoded pulse disc made of glass or plastic. Inside the sensor senses an optical system from this disc. The strengths of optical encoders are its ability to capture high resolutions and speeds, as well as their magnetic resistance. Impractical, however, is that the devices achieve high resolutions only with large housing sections.

The greatest disadvantage is, however, the design-related direct mechanical coupling of the rotating shaft with the coded glass disc. Blows to the shaft may damage the pulse wheel. Only the operation of vibrating waves is sensitive to the construction on time. The system operates electrically wear - but that does not help much if the mechanics surrendered prematurely. The manufacturers know the Achilles heel of the optical encoder and therefore attempt to minimize vibrations. Mounting accessories including clutches and spring elements to curb continuous mechanical load. Other manufacturers are equipping their encoder paired with ball bearings or put on gearless variants.

Potentiometric encoder: Included wear

All these attempts to cushion the basic design flaw of the device only. The mechanical connection between the engine shaft and encoder brings sooner or later wear damage with it - be it on spring elements, seals or the encoder itself Similarly, with the potentiometric rotary encoders: they too high resolutions at the expense of robustness. The manufacturer of the pot make no secret that a potentiometer is a consumable item, as well as a rotary encoder as other sensors.

Usually the seal of the encoder housing is the central weakness. Especially the permanent stress caused by high-speed shafts makes them eventually brittle, cracked and eventually leak. Penetrating water or dirt disturb the sensitive sensor and cause downtime. High protection classes meet optical and potentiometric encoder only as long as they are on the shelf.

Magnetic rotary encoder: EMC susceptible and intolerant

With the magnetic systems, it behaves mirrored. Its strength lies in a relatively high mechanical strength. The measuring principle is based on a rotating magnet, which builds a magnetic field and again discharges. Characterized a sine-cosine curve is generated and evaluated as a rotation signal. Magnetic encoders measure without contact and wear-free electronically. Your electronics can be built completely closed and sealed. The weaknesses of the available in the market but their magnetic encoders are EMC susceptibility and their intolerance of displacement of the magnet, which is why they must be operated in a housing that positions the donor EXAT. The limited resolution of magnetic devices is also dependent on the speed of the shaft to which they are coupled.

Combine advantages, disadvantages off

turck50413Turck has now developed an Encoder class, which works on the basis of inductive resonator measuring principle. The automation specialist has successfully used for two years in his position and angle sensors. The inductive rotary encoders turn RI360P-QR24 combine the advantages of the previous solutions and simultaneously elimieren their disadvantages. Not only are they completely wear-free, but also high-resolution, vibration-resistant, resistant to magnetic fields, high rotation and always meet IP69K protection.

The resonator measuring principle allows a construction without seals with fully sealed sensor housing, which is separated from the position sensor. The penetration of Dust or water in the electronics are so absolutely excluded. Vibration and displacement up to 4 mm, the encoder compensates with his non-contact measuring principle. Magnetic fields disrupt the measurement process anyway, since the position sensor is not based on a magnet, but in an inductive coil system, wherein the sensor and position transmitter (resonator) form a resonant circuit.

First application is waiting

turck20413The first customers are already waiting for the new encoder. Among them, a solar tower plant in Spain. These so-called heliostat power plants came all previously used encoders that are used to align the mirror on the central tower, to its limits. Since the mirror up to 1 km from Tower stand, must tilt changes in Milliradbereich (1 milliradians = approx 0,06 degrees) are converted to the light precisely to project onto the tower. Magnetic encoders come here because of the lack of resolution of the question. Optical encoders are the climatic challenges in desert regions of permanent no match: Hot days and cold nights cause severe condensation formation. In an un-encapsulated system can not prevent water pockets. The penetrating water disturbs the electronics and the optics, the sensor fails. Since solar power towers are often in remote areas and extend over several square kilometers, is the replacement of a single encoder is particularly great effort.

The maintenance-free RI encoder is superior to optical encoders far here, as shown in the economic analysis: In the mentioned power plant are about 20.000 optical encoders installed. Per year had to replace the operator about a third of them because they were broken or just before a failure. At a price of Euro 100 caused losses of almost 700.000 euros a year. In addition, the costs for service technicians and the damage caused by fallen electricity come. The total damage alone in this project thus amounted to around 1 million euros annually.

Universal encoder replaces several types 100

With the new encoder, the user must not compromise between resolution and robustness make more. Eliminates the need for all efforts, the encoder over springs or double bearings to protect against mechanical stress. In addition to the interference and the freedom to wear the system, the user also benefits from the parameterization and mounting concept that makes a single encoder model for universal encoder for countless applications. This one model can replace several 100 various encoder types. The assembly concept continues universal approach: About adapter rings, the user can use the position sensor on shafts of different diameters. He must only retain a single rotary encoder available, he can use all applications on waves up 20 mm.

Configurable IO-Link version

turck40413Turck initially brings a configurable IO-Link version to the market. About the Parametrierungsschnittstelle IO-Link, the user can tune the characteristics and all parameters of the encoder individually on his application. Thus the device can be parameterized as a multi-turn, single-turn or incremental encoders. The encoder can be particularly high resolutions up 18 bit, even at high speeds can be set. The output signals, the customer can be parameterized individually: as SSI, Gray code or Binar signal in 24, 25 or 26 bit, incrementally, and voltage or current output. After the IO version will follow in the coming months, further variants: one with Mode RTU port and a constructed according e1 directive variant for use in mobile machines with voltage output of ... 0,5 4,5 V.

As flexible as the Parametrierungskonzept of the sensor is also his assembly concept. About the adapter shaft encoders on all major solid and hollow-shaft thicknesses up 20 mm can be used. The sensor has the shape of a donut and can be pushed with its center hole and the shaft, the position sensor can be positioned either behind or in front of - depending on how it is built, the local conditions allow.

Machine tool and many other applications

turck30413Not the new encoder model that can be classified in the available drawers, also shows the desire of customers in the machine tool industry. This application differs most from the use of the solar power plant: While the acquisition of solar panels is in the single-turn range and very slow, but its precision has, the application moves to the CNC machine in multiturn and requires the acquisition with about 25.000 up min-1. The rate is for the RI360P-QR24 no problem, because in contrast to all other devices on the market, the rotary encoder is not mechanically limited to a maximum speed.

The markets for the new encoder class are as varied as their configuration options. Among other things, the manufacturer sees in mobile machinery, renewable energy, packaging machines, machine tools, logistics systems and facilities is enormous potential. By design, the new encoder class but suitable for all markets and nearly all fields of application.

The author André brewer's product manager linear position sensors and encoders at Hans Turck GmbH & Co. KG, Mülheim.


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