10-02-2020 | | By Nnamdi Anyadike
Cable pull or draw wire encoders continue to shrink in size and now one company, Kübler, has unveiled what it claims is the thinnest cable encoder on the market. A draw-wire encoder is essentially a linear measuring device that consists of a spring-wound cable reel with a rotary encoder mounted on the hub of the reel. The cable is attached to a load, which draws out the wire as the reel turns causing the encoder to rotate and transmit the amount of rotation either as a voltage pulse stream (incremental encoder) or digital word (absolute encoder). Output can also be provided as analogue linear voltage output or as output from a resolver.
Cable pulls are most commonly paired with absolute rotary encoders. These can provide a position measurement as soon as they are powered up. And they can do this even if the position is changed after the encoder is switched off. Absolute rotary encoders use a variety of communication protocols, such as DeviceNet, EtherNet/IP, PROFIBUS, CANopen, and PROFINET.
In January, the Villingen-Schwenningen, Germany based Kübler Group, one of the world's leading specialists in position and motion sensors, process and transmission technology, unveiled a cable pull encoder that it describes as the thinnest on the market. Its wire-rope encoder is an upgrade of an earlier version. This earlier version is already used in mobile machines, work and rescue platforms, and driverless transport systems and in general automation. The upgrade now offers a redundant analogue sensor. This allows for the implementation of additional new security concepts using this variant or the redundant sensors. “The cable mechanism can be combined with various sensors. This means that analogue, incremental and field-bus interfaces can be freely selected,” the company explained.
Pepperl+Fuchs GmbH the Mannheim, Germany based developer and manufacturer of industrial sensor technology, has developed a range of rotary encoders that monitor acceleration, speed, and direction. They compile data on shaft rotation and convert it to an analogue or digital output signal and communicate this data using a number of industrial communication protocols. The company has solved the problem of ensuring operability in an outdoor environment with its robust ECN30 cable pull, which the company claims is capable of withstanding ‘extreme outdoor’ applications. The company explained, “Standard cable pull encoders contain mechanical parts. Therefore, they must be kept lubricated and maintained to ensure long use. But to reduce the need for maintenance and to enhance linear movement detection performance, we have paired the cable pull with a magnetic rotary encoder. These use no mechanical gears in their sensing system, thereby making them more durable.” Instead of mechanical gears, the encoder uses its internal magnetic sensors and a magnetic disk to detect movement and the position of an application. Pepperl+Fuchs have also made available its ECA10TL cable pull rotary encoder, either as analogue or with an EtherCAT or PROFINET interface.
Micro-Epsilon UK & Ireland Ltd recently unveiled its new ‘K series’ of draw wire sensors, designed for demanding outdoor measurement tasks. Their compact and robust housing made from glass-fibre reinforced plastic and their durable sensor design with separate drum and spring spaces offer increased protection against environmental influences. And their modular potentiometer sensor design enables fast and low cost OEM customisation. These potentiometer sensors measure the distance or displacement of an object in a linear or rotary motion and convert them into an electrical signal. In addition, the company markets ‘P series’ of draw-wire sensors of the P series for industrial measurements. The sensors come in analogue versions with potentiometer, current or voltage output and digital versions with incremental or absolute encoders.
Siko GmbH, the German based electronics manufacturer, recently launched its new magnetic absolute linear MSA213C high-resolution absolute sensor. It supplies absolute positioning at any time without referencing and without requiring a backup battery. “With its small design and many different interfaces, it can also be integrated into an existing system and control environment with little effort,” the company said. The MSA213C has a high signal quality and is designed for precise position detection and speed measurement in linear direct drives. It features high absolute resolution of 1 μm and achieves this performance level over a length of up to 16 m. It is available in the basic versions with SSI, RS485 and BiSS-C. It is also available with IO-Link and it supports protocols from various control unit manufacturers.
A recent study points to the encoder market growing at a CAGR of 8.6%, from $1.6 billion in 2019 to $2.4 billion by 2024. Key drivers include the need for high-end automation and industry 4.0. Can we expect Rotary encoders to continue driving the encoder market and hold the largest share?