Encoder offers high speed and efficiency

Dean Palmer reports on two novel rotary encoders that meet the increasing demand from users for reliable, low cost, high speed rotary feedback A frictionless, miniature magnetic rotary encoder has been developed that has a truly novel design which eliminates the need for seals or bearings and offers users speeds of up to 30,000rpm with measurement accuracy to 0.4 deg. Gloucestershire-based encoder specialist Renishaw is responsible for the new development and, according the company's marketing manager magnetic encoders Tom Mackintosh, "We believe the new device represents a major step forward in encoder technology. The devices are easy to integrate, with a range of formats offered, including component, modular and packaged versions. We've already had interest from a major US-based petrol pump manufacturer that is looking at how it can incorporate the devices in all of its service station pumps." 'Quietly' launched earlier this year at the UK Autosport show, then at last month's MTEC exhibition at the NEC, the new encoder is a viable alternative for customers currently using optical glass encoders. As Mackintosh explained to Eureka: "Optical encoders have to be cleaned and they are fragile in harsh environments. Our magnetic encoder is non-contact and so has an endless life." RLS, a Slovenian company recently acquired by Renishaw, is behind the encoder's new on-board ASIC (application specific integrated circuit), which has a diameter of just 8 sq mm. The encoder is absolute and provides up to 12-bit resolution in parallel or serial data formats, whilst other output options include incremental, analogue, linear voltage and linear current. The linear voltage or current output options can be used in applications such as panel switches where, traditionally, potentiometers have been used. The encoder has an extended temperature range from -25 deg C up to 125 deg C, excellent shock and vibration resistance, is easy to install and set up, and has excellent reliability through its non-contact design. And for harsh environments, the company is also offering customers an IP68 version, which, according to Mackintosh, can be used underwater to a depth of 10m. Mackintosh told Eureka: "With such a flexible design, applications will vary from mobility devices and marine instrumentation to valve position control, vending machines, industrial power tools and motor feedback." The devices may also interest process manufacturers for washdown applications; semiconductor machine makers; marine antennae; printing (computer-to-press) machine builders; and could be used for CCTV applications. Renishaw has also developed an innovative incremental rotary (angle) encoder that also boasts high resolution and reliability. As Ian Oliver, UK business manager explained: "The new one-piece, RESR rotary encoder has a very high accuracy, with resolution to 0.01 arc second. The device has a unique taper mount system that ensures easy installation and adjustment to minimise errors. It's also fitted with our RGH20 filtering readhead and so has a high tolerance to dirt, scratches and greasy fingerprints that can cause other encoder systems to 'miscount'." The design of the RESR is based on the company's unique RGR ring encoder that uses a flexible linear scale around a stainless steel ring. But the 'new' element of the latest RESR is it has the scale grating (20(m or 40(m) marked directly onto the periphery of the ring, which eliminates the potential for signal loss at the join, simplifies set up and enables higher speeds. The RESR comes in a wide range of sizes and line count options to ensure compatibility with the various industry standard controllers. Line counts for example range from 4,096 to 64,800. Pointers * The new encoder has a very high measurement accuracy of 0.4 deg and a speed of up to 30,000rpm * The encoder has an 8 sq mm ASIC that offers 12-bit resolution (4,096 count) in parallel or serial data formats * One of the US' leading petrol pump manufacturers is considering using the device for its petrol station pumps