12/10/2014
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`Fifty years old: the proximity switch
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`Fifty years old: the proximity switch
`
`29 November 2008
`
`In 1958—exactly 50 years ago—the proximity switch was invented in a Mannheim laboratory owned by Pepperl+Fuchs. What was originally conceived as a customer
`specific solution for an intrinsically safe current circuit in the chemical industry, has since become the universally recognised industry standard for noncontact
`switching.
`
`The proximity switch is one of the oldest electronic components in automation. It has been continuously reinvented over
`the years to keep pace with everchanging requirements.
`
`Fifty years ago, when Walter Pepperl and his colleague Wilfried Gehl were commissioned by BASF to find an alternative to
`mechanical contacts, they had no idea that they would set a milestone in the development of automation technology. The
`challenge was to develop a robust component that would operate reliably after many thousands of switching cycles at very
`low switching currents, in the corrosive atmosphere of a chemical plant.
`
`As trained radio engineers, they knew what happens when a metallic object approaches a coil system. With the bipolar
`transistor, which William B. Shockley had invented 10 years earlier, the two engineers had at their disposal a new
`compact component with which the damping of an oscillating circuit could be easily evaluated and converted into a
`switching signal. The invention of the proximity switch is consequently an early example of how communications
`engineering expertise advances automation technology.
`
`In the early years, application of the inductive proximity switch was restricted to the chemical industry, where problems
`with mechanical contact wear due to the low currents used and the resulting absence of cleansing through contact
`erosion, were the most severe.
`
`The first proximity switch
`
`However, in the early 1960s, people began to appreciate the practically unlimited service life of these switches in other automation applications. So it was no surprise when
`Pepperl+Fuchs introduced an inductive version of the roller lever limit switch on the market in 1968. This device shared mounting compatibility with its mechanical counterpart
`and had the option of five different positions for the active sensor surface, so that any possible travel direction of the mechanical switch could be replicated.
`
`In those days it was not yet possible to reproduce all the different voltage ranges electronically. Nevertheless, the 60 different versions of proximity switch required as a result
`could not prevent its success on the market. The absence of wear was a major advantage for the reliability of automation systems.
`
`Ten years later, the nextgeneration device was presented, which simplified applications. The user could now change the active sensor surface himself and the amplifiers with
`different voltage ranges could be easily replaced by insertion. This proximity switch design continues to be one of the highest selling, but the development of this technology has
`resulted in much greater variety.
`
`VERSATILITY OF THE PROXIMITY SWITCH
`
`The most familiar proximity switch design is the cylindrical threaded bushing. Its design resembles a threaded stud and, consequently, it can be easily mounted on any machine.
`The sturdy brass or stainless steel housing protects the electronics against all types of environmental influence and, of course, mechanical destruction.
`
`Moreover, there are hundreds of other designs available on the market today, taking account of the various installation requirements in machine manufacturing. This sensor is
`probably one of the few electronic components whose housing design must be adapted to the application rather than to the packaged electronics. Versatility is therefore a matter
`of course.
`
`In the 1990s, proximity switch electronics were further developed. Integrated circuitry was introduced, which extended functionality and improved EMC interference immunity.
`New oscillator concepts enabled switches with a reduction factor of 1 to have the same switching distances for different metals. For applications with especially high durability
`requirements, proximity switches are available with active sensor surfaces made of stainless steel. Extremely sensitive evaluation is required for such applications, as the pre
`damping of the oscillator through the end surface of the housing is quite significant.
`
`Microcontrollers have now also become established in proximity switches. These enable even higher switching distances to be achieved and provide for simplified adjustment of
`components in production, in addition to improved functionality. All this in a device which is subject to constant price pressure owing to the very high unit volume requirements.
`
`These facts show that the development of the proximity switch has never stopped over the last fifty years. Driven on by
`incessant new requests and requirements from machine manufacturing and plant engineering, the proximity switch has
`been continuously reinvented and this trend is set to continue into the future.
`
`ANALOGUE POSITION MEASUREMENT
`
`There are several reasons for the market success of the proximity switch. On the one hand, the coil as sensor element is
`costeffective to produce and evaluate. On the other hand, these switches are extremely sturdy, easy to use and reliable.
`Soiling or other environmental influences hardly effect their function. These properties distinguish the proximity switch
`favorably from other types of sensor. It is therefore no surprise that the quantities sold have increased dramatically in
`recent years, with no sign of a downturn currently in sight.
`
`And there are some interesting applications in automation technology that exploit the basic principle of the proximity
`switch and provide the same benefits to the user. Analogue position measurement is a good example of such an
`application.
`
`Prox switch in 1968 (left)
`For this purpose, multiple coils are arranged in a row to precisely measure the horizontal displacement of a metal target to a tenth of a millimeter. A microcontroller evaluates the
`damping of the different coils by the target and thereby calculates the exact position. The measurement result is independent of the precision of the vertical guidance of the target.
`This is a good example of how a fiftyyearold principle can be transformed into a reliable and easytouse displacement measurement system with the aid of modern electronic
`technology.
`
`Sensors as the sensory organs of machines are indispensable in the field of automation. In principle, it is merely a matter of transforming physical events into electrical ones. The
`coil as a sensor element for the proximity switch has established itself as an almost perfect device for position recognition. As long as machines are constructed primarily from
`metallic materials, the further success of the proximity switch is assured.
`
`THE LATEST PROXIMITY SWITCHES
`
`A good example of the latest in proximity sensor design is one created by the inventor himself: the VariKont®. These new representatives of Pepperl+Fuchs proximity switches
`feature a revised modern housing design, identical standard dimensions, and technical stateoftheart inner workings. The new generation of inductive proximity sensors
`combines innovation with tried and tested technologies. The connectors at the lower housing sections are compatible with previous models, so users will not have troublesome
`adjustments and installations.
`
`The VariKont design is a classic in the history of the inductive proximity switch. The housing shape developed by Pepperl+Fuchs prevailed on the market and was even
`standardised according to ISO norm.
`
`ALLANGLE DISPLAY
`
`The inductive sensors were literally perfected across all corners and edges. Four of the eight rounded corners are equipped with display LEDs. The operating and switching
`states are displayed on two green and two yellow LEDs arranged crosscorner. This makes it possible for users to see all status information regardless of the angle of view, which
`
`http://www.controlengeurope.com/article/20839/Fiftyyearsoldtheproximityswitch.aspx
`
`1/2
`
`MICROSOFT EXHIBIT 1008
`
`
`
`Fifty years old: the proximity switch
`
`Like
`
`0
`
`Tweet
`
`0
`
`0
`
`Fifty years old: the proximity switch
`
`29 November 2008
`
`In 1958—exactly 50 years ago—the proximity switch was invented in a Mannheim laboratory owned by Pepperl+Fuchs. What was originally conceived as a customer
`specific solution for an intrinsically safe current circuit in the chemical industry, has since become the universally recognised industry standard for noncontact
`switching.
`
`The proximity switch is one of the oldest electronic components in automation. It has been continuously reinvented over
`the years to keep pace with everchanging requirements.
`
`Fifty years ago, when Walter Pepperl and his colleague Wilfried Gehl were commissioned by BASF to find an alternative to
`mechanical contacts, they had no idea that they would set a milestone in the development of automation technology. The
`challenge was to develop a robust component that would operate reliably after many thousands of switching cycles at very
`low switching currents, in the corrosive atmosphere of a chemical plant.
`
`As trained radio engineers, they knew what happens when a metallic object approaches a coil system. With the bipolar
`transistor, which William B. Shockley had invented 10 years earlier, the two engineers had at their disposal a new
`compact component with which the damping of an oscillating circuit could be easily evaluated and converted into a
`switching signal. The invention of the proximity switch is consequently an early example of how communications
`engineering expertise advances automation technology.
`
`In the early years, application of the inductive proximity switch was restricted to the chemical industry, where problems
`with mechanical contact wear due to the low currents used and the resulting absence of cleansing through contact
`erosion, were the most severe.
`
`The first proximity switch
`
`However, in the early 1960s, people began to appreciate the practically unlimited service life of these switches in other automation applications. So it was no surprise when
`Pepperl+Fuchs introduced an inductive version of the roller lever limit switch on the market in 1968. This device shared mounting compatibility with its mechanical counterpart
`and had the option of five different positions for the active sensor surface, so that any possible travel direction of the mechanical switch could be replicated.
`
`In those days it was not yet possible to reproduce all the different voltage ranges electronically. Nevertheless, the 60 different versions of proximity switch required as a result
`could not prevent its success on the market. The absence of wear was a major advantage for the reliability of automation systems.
`
`Ten years later, the nextgeneration device was presented, which simplified applications. The user could now change the active sensor surface himself and the amplifiers with
`different voltage ranges could be easily replaced by insertion. This proximity switch design continues to be one of the highest selling, but the development of this technology has
`resulted in much greater variety.
`
`VERSATILITY OF THE PROXIMITY SWITCH
`
`The most familiar proximity switch design is the cylindrical threaded bushing. Its design resembles a threaded stud and, consequently, it can be easily mounted on any machine.
`The sturdy brass or stainless steel housing protects the electronics against all types of environmental influence and, of course, mechanical destruction.
`
`Moreover, there are hundreds of other designs available on the market today, taking account of the various installation requirements in machine manufacturing. This sensor is
`probably one of the few electronic components whose housing design must be adapted to the application rather than to the packaged electronics. Versatility is therefore a matter
`of course.
`
`In the 1990s, proximity switch electronics were further developed. Integrated circuitry was introduced, which extended functionality and improved EMC interference immunity.
`New oscillator concepts enabled switches with a reduction factor of 1 to have the same switching distances for different metals. For applications with especially high durability
`requirements, proximity switches are available with active sensor surfaces made of stainless steel. Extremely sensitive evaluation is required for such applications, as the pre
`damping of the oscillator through the end surface of the housing is quite significant.
`
`Microcontrollers have now also become established in proximity switches. These enable even higher switching distances to be achieved and provide for simplified adjustment of
`components in production, in addition to improved functionality. All this in a device which is subject to constant price pressure owing to the very high unit volume requirements.
`
`These facts show that the development of the proximity switch has never stopped over the last fifty years. Driven on by
`incessant new requests and requirements from machine manufacturing and plant engineering, the proximity switch has
`been continuously reinvented and this trend is set to continue into the future.
`
`ANALOGUE POSITION MEASUREMENT
`
`There are several reasons for the market success of the proximity switch. On the one hand, the coil as sensor element is
`costeffective to produce and evaluate. On the other hand, these switches are extremely sturdy, easy to use and reliable.
`Soiling or other environmental influences hardly effect their function. These properties distinguish the proximity switch
`favorably from other types of sensor. It is therefore no surprise that the quantities sold have increased dramatically in
`recent years, with no sign of a downturn currently in sight.
`
`And there are some interesting applications in automation technology that exploit the basic principle of the proximity
`switch and provide the same benefits to the user. Analogue position measurement is a good example of such an
`application.
`
`Prox switch in 1968 (left)
`For this purpose, multiple coils are arranged in a row to precisely measure the horizontal displacement of a metal target to a tenth of a millimeter. A microcontroller evaluates the
`damping of the different coils by the target and thereby calculates the exact position. The measurement result is independent of the precision of the vertical guidance of the target.
`This is a good example of how a fiftyyearold principle can be transformed into a reliable and easytouse displacement measurement system with the aid of modern electronic
`technology.
`
`Sensors as the sensory organs of machines are indispensable in the field of automation. In principle, it is merely a matter of transforming physical events into electrical ones. The
`coil as a sensor element for the proximity switch has established itself as an almost perfect device for position recognition. As long as machines are constructed primarily from
`metallic materials, the further success of the proximity switch is assured.
`
`THE LATEST PROXIMITY SWITCHES
`
`A good example of the latest in proximity sensor design is one created by the inventor himself: the VariKont®. These new representatives of Pepperl+Fuchs proximity switches
`feature a revised modern housing design, identical standard dimensions, and technical stateoftheart inner workings. The new generation of inductive proximity sensors
`combines innovation with tried and tested technologies. The connectors at the lower housing sections are compatible with previous models, so users will not have troublesome
`adjustments and installations.
`
`The VariKont design is a classic in the history of the inductive proximity switch. The housing shape developed by Pepperl+Fuchs prevailed on the market and was even
`standardised according to ISO norm.
`
`ALLANGLE DISPLAY
`
`The inductive sensors were literally perfected across all corners and edges. Four of the eight rounded corners are equipped with display LEDs. The operating and switching
`states are displayed on two green and two yellow LEDs arranged crosscorner. This makes it possible for users to see all status information regardless of the angle of view, which
`
`http://www.controlengeurope.com/article/20839/Fiftyyearsoldtheproximityswitch.aspx
`
`1/2
`
`MICROSOFT EXHIBIT 1008
`
`
`
`Fifty years old: the proximity switch
`12/10/2014
`is a clear advantage during startup, servicing, or troubleshooting. The layout of the LEDs is patented, assuring that competitors will not reach the same high degree of
`functionality.
`
`The corner LEDS were introduced in 2003 with the Varikont L sensor, the smaller sensor designed for interior spaces and without need for a separate terminal compartment.
`
`The sensor head houses all sensor system components and analysis electronics while the base section features the
`elements for the mechanical fastening as well as the terminal compartment for electrical installation. Three screws are
`used to connect the function section with the premounted and electrically connected mounting unit. Easy installation and
`setup and speedy replacement, especially in case of servicing, without electrical connection work are the result.
`
`INDESTRUCTIBLE UNDER SEVERE CONDITIONS
`
`Among the secrets of the success of the VariKont ’variable contact switch‘ are its ruggedness and reliability under all
`conceivable operating conditions concerning interior and exterior applications. Pepperl+Fuchs has improved these
`essential properties for the new VariKont inductive sensor. The impermeability and ruggedness of the housing now meets
`the requirements of protection class IP67 and IP69k. This means the new sensors are even more weather resistant, water
`proof, heatresistant, and impactresistant. Improved UVresistance also protects the units from the damaging rays of the
`sun. Together with the new sealing concept, VariKont proximity switches are even better protected from moisture when
`used outside.
`
`The new sensor now offers all switching distances from 20 mm to 40 mm in standardsized housing. Previously, switches
`VariKont prox switch
`with 40mm switching distance were only available with larger housings. Also new are inductive sensors with reduction factor 1. They offer an ideal solution if frequently changing
`workpieces made from iron, aluminium, or other light metals are processed, like in the automotive industry. In systems where many electronic devices work together in a confined
`space, the optimised electromagnetic behaviour makes the proximity switches resistant to external interferences. VariKont sensors are npnswitching, pnpswitching as NC or NO
`contact in 2wire, 3wire, or 4wire variants usually available on the market.
`
`A LEVEL HIGHER
`
`A modern design and extensive enhancements concerning the electrical and mechanical properties as well as a cleverly designed "allangle" status display mean the new
`VariKont inductive proximity sensor generation offers users the latest maximum of functionality and user benefit. The properties of the sensors and switches enable a reliable and
`stressfree operation and come one step closer to the zerofault principle. Since the triedandtested connection system between upper and lower sensor section was also
`applied to the new models, users are easily able to replace old sensors with the new counterparts to upgrade their systems without complex installation work. The existing wiring
`and connection technology can be maintained unchanged.
`
`—Dr. Peter Adolphs, General Manager Factory Automation, Pepperl + Fuchs
`
`Dipl.Wirtsch.Ing. (FH) Thomas Hensler contributed to the writing of this article.
`
`PHOTO CAPTIONS
`
`Figure 1: The first inductive proximity switch, manufactured in 1958
`
`Figure 2: A proximity switch from 1968. It is functionally compatible with the roller lever switch shown on the right.
`
`Figure 3: The 360 degree allangles view function is one of the highlights of the new VariKont generation. This function makes it possible to see all operating and switching states
`during installation and setup as well as during normal operating mode. Improved UVresistance with the proper material selection and a revised sealing concept reliably keep
`moisture away from the inside of the sensor even after many years of outside use.
`
`Contact Details and Archive...
`Pepperl+Fuchs Gmbh
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