A renaissance for incremental rotary encoders
14 November 2009
The world’s first and only TÜV-certified safety incremental rotary encoder opens the way to new applications for machine and plant safety— up to SIL3 or PL e.
Incremental rotary encoders are sensors that have used the same basic technology for over 50 years. During this time they have been steadily developed to achieve higher performance and longer service life at an ever lower price.
Incremental rotary encoders, which are also known as quadrature encoders, are still indispensible today due to their high dynamics and resolution, which comes through interpolation.
Functionally safe rotary encoders also present a brand new challenge against the background of the new Machinery Directive (2006/42/EC).
Introduced recently to the market by Pepperl+Fuchs, the RVS58S incremental rotary encoder has integrated safety technology and self-diagnostics specifically designed for use in safety systems—up to safety categories SIL3 or Pl e.
This opens up new fields of application for incremental rotary encoders, such as safe drive technology or rotational speed monitors No other incremental rotary encoder can achieve this without additional redundancy.
At first glance, the RVS58S looks like an ordinary incremental rotary encoder, since both the design as well as the electric interface are compatible with the standard ranges on the market. This makes integration into existing concepts simple.
Inside, however, a highly developed rotary encoder operates with the lowest of failure rates, comprehensive self-diagnosis and utmost precision in order to meet the high demands of safety category SIL3 or PL e.
Functionally safe drives
The manufacturing industries are seeing more machines that are pushed to higher performance by running them at higher speeds. In this environment a whole range of robots and automatic feed systems are operating faster, in order to reduce the workload of operating personnel.
And system operators are employing increasingly higher machine speeds in order to optimise production costs.
Examples such as those found in the packaging or printing industries highlight the sober fact that, with increased speed also comes the possibility of increased risk.
The important prerequisites for preventing this are quick machine stops and short reaction times.
According to the Machinery Directive and relevant safety regulations for health and safety at the workplace, even brief lapses in attention must not result in shearing, crushing or impact injuries.
The RVS58S can be connected to modules from a wide variety of manufacturers. It reachs a safety category up to SIL3 or PL e with a single rotary encoder per axis.
As it is the high-powered drives that produce the action of force, these systems are especially important. The preferred use of rotary encoders is to monitor rotating or swivelling components in drive systems, making them a core safety consideration in drives.
But it is not just conventional safety considerations which, when properly implemented, lead to productivity increases and thus to cost optimisation.
Architecture also leads to savings potential by reducing external safety components. This is implemented using a drive-based safety concept, whereby safety-relevant functions are integrated into the drive control.
Traditionally increased safety has been achieved with two-channel operation, without completely duplicated execution of the functional units. or with dual encoders or two rotary encoders. This increased number of components of course increases the system cost.
In many production process situations, it is even possible to increase productivity at reduced speeds. Shutting down machines costs time and money. It is more efficient to protect a plant in such a way that standstills for safety reasons are not necessary during maintenance and operation.
As no additional sensors are required for RVS58S, and standard interfaces are used, integration into drive controls is particularly simple.
To transmit an error condition, which is necessary to achieve high safety categories, the already existing lead or sensor breakage detection is usually used. As well as these special requirements for safety technology, the RVS58S also meets those requirements for drive technology incremental sine/cosine rotary encoders, even in special versions that operate in temperatures up to 115°C.
Trust is good, control is better
For several years now, the trend in safety technology has moved toward freely programmable systems. In machine manufacturing, flexibility and cost-efficiency are given top priority.
Consequently, both smaller and more modular rotation speed monitors in the form of system components, are used.
And added to this increase in safety technology are the complex safety PLCs now available.
Regardless of supplier or complexity, simple and flexible implementation is an important stipulation.
The key to cost optimisation lies in using fewer components with flexible use, away from redundant systems. Both the cost of repeat components, as well as the associated mounting and maintenance, incur unnecessary outlay.
Impressing the judges
Less is more: a trend which can effectively be followed with functionally safe components.
The RVS58S, which can be connected to modules from a wide variety of manufacturers, can reach a safety category up to SIL3 or PL e with a single rotary encoder per axis.
For multi-spindle machine tools or multi-axle packaging machines, dispensing with redundant sensors and control units provides enormous savings potential. Via the standard 1V peak-to-peak sine/cosine interface, considerably higher rotational speed resolutions can be achieved than with digital incremental rotary encoders.
The RVS58S thus covers a very wide bandwidth for safe detection of rotational speed, in particular in the lower rotational speed range, which is an important criterion in choosing suitable rotary encoders.
A convinced jury
The RVS58S impressed a neutral panel of judges, consisting of experts and representatives from ZVEI, VDMA, BHE and TÜV, who nominated the encoder for Category A ‘Safe Automation’ of the GIT Security Award 2010.
The high safety category, very wide detection area, no redundant sensors and simple integration via standard interfaces not known in any other rotary encoder convinced the GIT Security Award jury.
Moreover, it is the simple integration into existing control concepts that distinguishes this product and also makes it versatile for retrofitting.
For more information about the GIT Security Award 2010, visit http://www.pro-4-pro.com/en/Safety-Security/Poll/index.html#
The RVS58S opens up enormous potential for optimising safety and productivity. Benefit today from that which sets the standard for the future: a new age in incremental rotary encoder technology is experiencing a renaissance and guarantees a further generation with a promising future for a product series that has proven itself a million times over.
RVS58S Encoder At a Glance
Pulse count — 1024 and 2048
Operating voltage — 5V dc ±5%
No-load supply current — 70mA
Output — Sine/cosine
Amplitude — 1V peak-to-peak
Output frequency — max. 200 kHz
Max. speed — 12,000 RPM
Weight — 350g
Temperature — -5 to 80 deg C, (movable cable); -20 to 80 deg C (fixed cable)
special versions to 115 deg C
—Author: Dipl.-Ing. Oliver Springmann, Product Management, Encoders, Pepperl+Fuchs Drehgeber GmbH, Tuttlingen
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