Smart solution with frequency sweep technology – A level switch for all media!

20/11/2013

Fill levels must be recognized in countless storage, buffer and holding tanks in the process industry, food industry, and even in wind power plants or other fields. The level switches used are normally as different as the various media being monitored. With the CleverLevel LBFS/LFFS switch, Baumer has developed a true all-rounder that uses frequency sweep technology. This method capitalizes on the fact that every material, regardless of its consistency, has a dielectric constant specific to that medium. This makes the new level switch suitable for practically all media, including liquids, granulates and even electrostatic media. At the same time, it is unaffected by adhesive substances or foams that may lead to switching errors with other technologies. Furthermore, it can distinguish between different media. This makes the CleverLevel more than merely a replacement for the traditional vibrating fork used in level control. Configuration is possible using Teach-in. It is more convenient with Flex Programmer software, which enables visualization at the same time. The displayed information can be communicated to a higher-level controller if required and interpreted there in accordance with the operation phase.

Level control in a container

Level control in a container

Level detection is of great importance in the process industry. They monitor maximum and minimum values of material fill levels in tanks or as protection against overflow or dry operation. A number of limit switches are available, based on different technologies. The specific application determines the selection, because until now it was not possible to cover all applications with one level switch. Things are different now. A new level switch that uses frequency sweep technology now proves to be a practice-oriented all-rounder for almost every conceivable medium.

The demands on level switches can vary considerably, depending upon application. There are therefore numerous application-specific factors to consider, such as foam formation, aggressiveness or flammability of the media to be detected, adhesive substances, unfavorable installation conditions, the speed of the filling process and, naturally, the accuracy required. The widely used vibrating forks do not necessarily offer the best conditions. Some have quite large components that extend far into the material being measured. Measuring errors can arise, since high viscosity materials tend to stick to these forks. Coarse granular media can easily become lodged between the forks and also cause measuring errors. The forks and difficult to clean and liquid and powder substances require different versions. It was impossible to cover all applications with one level switch, until now.

Versatile sensor with elegant configuration

The CleverLevel series of level switches use frequency sweep technology and can reliably detect extremely different media. The readings are not affected by adhesive substances or foam.

The CleverLevel series of level switches use frequency sweep technology and can reliably detect extremely different media. The readings are not affected by adhesive substances or foam.

Now the Baumer CleverLevel series of level switches fill this gap. They are based on frequency sweep technology. The sensor analyses the resonance frequency of the oscillating circuit affected by the dielectric constant of the medium below the sensor tip. This allows adhesive substance on the sensor tip or foam to be suppressed. High sensitivity over a large measurement range for dielectric constants from 1.5 to over 100 enables limit detection for all sorts of powders, granulates and liquids. And setup is easy.

The default setting already recognizes most media. The Teach-in function helps in case of doubt and more complex configuration becomes child’s play with the FlexProgrammer software, because the user can practically “see” the same thing as the sensor. The switching range can be adjusted as required to ignore foams in maximum or minimum monitoring, for example. The same applies if the sensor needs to ignore adhesive substances. Tanks with liquid chocolate are a typical example. Even when empty, the sensor and container walls are coated with chocolate. When configured accordingly, the CleverLevel still switches only when the tank is really full or empty. Electrostatic adhesion, which must frequently be taken into account in the detection of powdery substances, can also be ignored by appropriate definition of the switching range.

The simple, graphic configuration software really adds to the user-friendliness. For example, it is possible to observe the sensor’s internal signal while the thresholds are adjusted by mouse click within the graphic representation. This not only makes the configuration method intuitive and thus easily learned, but also considerably improves the reliability of the results, because they can be checked graphically at any time. This is also possible with extended setting methods that take medium conductivity into account, even if two media have the same dielectric constant.

Supported by the FlexProgrammer, the CleverLevel series can perform even complex filling level detection tasks.

Supported by the FlexProgrammer, the CleverLevel series can perform even complex filling level detection tasks.

Even different media in the same process line or process tank can be detected in order to differentiate the end product. For example, different types of fish sauce, different beers, etc. For this purpose a measuring signal can be output so that different dielectric constants through different media, foams or adhesive substances can be differentiated in the control. This makes it possible to detect if a medium is polluted with another medium, e.g. oil polluted with water.

Assessment of measurement results and maintenance planning

The information that is visualized with the help of software can also be transferred to the higher-level controller. It can then evaluate the measuring signal. It ultimately knows if the position of the switching point shifts because another medium is in the tank during flushing, for example. Dirt in the tank can also be detected in this way and cleaning can be scheduled accordingly. Today, many application areas are dependent upon this information. Wind power plants are a typical example of this, because “spontaneous” maintenance of lubricant containers is extremely costly and can only be carried out at unjustifiable expense. The same applies to locomotives, ships or mobile implements in agriculture, for example.

Using the Flex Programmer software, the switching range can be adjusted as required to ignore foam during maximum or minimum monitoring.

Using the Flex Programmer software, the switching range can be adjusted as required to ignore foam during maximum or minimum monitoring.

A further strength of the level-monitoring sensor is particularly evident in mobile tanks. It normally works with a response time of 0.1 sec., which permits high-speed filling processes and the precise maintenance of filling levels. However, this becomes a disadvantage if the tank is in motion and the contents slosh around. In such cases, a switching delay of up to 10 sec. can be set to avoid false signals due to tank movement.

Robust, hygienic, with ATEX approval

But the new CleverLevel series offers even more. The level switches can be installed in any position, even in rather inaccessible locations. The LED that signals the switching process is highly visible in all directions. The sensor works silently, compliance with protection class IP67 requirements is standard, and it is suitable for ambient temperatures between -40°C und +200°C. Operation is also unaffected by vibrations. For example, the latter is important if the level switch is placed close to a pump as protection against dry running. The small penetration depth of only 15 mm is also a positive feature in these circumstances. Flow and pressure are hardly affected. In addition, thanks to gap-free installation and the smooth tip, nothing can adhere to the sensor.

There are countless areas of application for this fill level sensor all-rounder, such as filling liquid chocolate.

There are countless areas of application for this fill level sensor all-rounder, such as filling liquid chocolate.

In addition to the industrial process connections, there are also versions with EHEDG approval and an ATEX version for Ex areas for applications with stringent hygiene requirements. There are countless application possibilities for this all-rounder level switch. The food and beverage industry can benefit from its possibilities as much as every other industry, from pharmaceuticals, chemicals, petrochemicals, and process engineering all the way to the water supply and wastewater fields. Further areas of application are found in wind power plants, mobile machinery, cereal mills or cleaning facilities and pumping systems.

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Smart solution with frequency sweep technology – A level switch for all media!

31/10/2013

Fill levels must be recognized in countless storage, buffer and holding tanks in the process industry, food industry, and even in wind power plants or other fields.

The level switches used are normally as different as the various media being monitored. With the CleverLevel LBFS/LFFS switch, Baumer has developed a true all-rounder that uses frequency sweep technology. This method capitalizes on the fact that every material, regardless of its consistency, has a dielectric constant specific to that medium. This makes the new level switch suitable for practically all media, including liquids, granulates and even electrostatic media. At the same time, it is unaffected by adhesive substances or foams that may lead to switching errors with other technologies. Furthermore, it can distinguish between different media. This makes the CleverLevel more than merely a replacement for the traditional vibrating fork used in level control. Configuration is possible using Teach-in. It is more convenient with Flex Programmer software, which enables visualization at the same time. The displayed information can be communicated to a higher-level controller if required and interpreted there in accordance with the operation phase.


Figure 1: Level control in a container.

Level detection is of great importance in the process industry. They monitor maximum and minimum values of material fill levels in tanks or as protection against overflow or dry operation. A number of limit switches are available, based on different technologies. The specific application determines the selection, because until now it was not possible to cover all applications with one level switch. Things are different now. A new level switch that uses frequency sweep technology now proves to be a practice-oriented all-rounder for almost every conceivable medium.

The demands on level switches can vary considerably, depending upon application. There are therefore numerous application-specific factors to consider, such as foam formation, aggressiveness or flammability of the media to be detected, adhesive substances, unfavorable installation conditions, the speed of the filling process and, naturally, the accuracy required.

The widely used vibrating forks do not necessarily offer the best conditions. Some have quite large components that extend far into the material being measured. Measuring errors can arise, since high viscosity materials tend to stick to these forks. Coarse granular media can easily become lodged between the forks and also cause measuring errors. The forks and difficult to clean and liquid and powder substances require different versions. It was impossible to cover all applications with one level switch, until now.

Figure 2: The CleverLevel series of level switches use frequency sweep technology and can reliably detect extremely different media. The readings are not affected by adhesive substances or foam.

Versatile sensor with elegant configuration
Now the Baumer CleverLevel series of level switches fill this gap. They are based on frequency sweep technology. The sensor analyses the resonance frequency of the oscillating circuit affected by the dielectric constant of the medium below the sensor tip. This allows adhesive substance on the sensor tip or foam to be suppressed. High sensitivity over a large measurement range for dielectric constants from 1.5 to over 100 enables limit detection for all sorts of powders, granulates and liquids. And setup is easy.

The default setting already recognizes most media. The Teach-in function helps in case of doubt and more complex configuration becomes child’s play with the FlexProgrammer software, because the user can practically “see” the same thing as the sensor. The switching range can be adjusted as required to ignore foams in maximum or minimum monitoring, for example. The same applies if the sensor needs to ignore adhesive substances. Tanks with liquid chocolate are a typical example. Even when empty, the sensor and container walls are coated with chocolate. When configured accordingly, the CleverLevel still switches only when the tank is really full or empty. Electrostatic adhesion, which must frequently be taken into account in the detection of powdery substances, can also be ignored by appropriate definition of the switching range.

The simple, graphic configuration software really adds to the user-friendliness. For example, it is possible to observe the sensor’s internal signal while the thresholds are adjusted by mouse click within the graphic representation. This not only makes the configuration method intuitive and thus easily learned, but also considerably improves the reliability of the results, because they can be checked graphically at any time. This is also possible with extended setting methods that take medium conductivity into account, even if two media have the same dielectric constant.

Even different media in the same process line or process tank can be detected in order to differentiate the end product. For example, different types of fish sauce, different beers, etc. For this purpose a measuring signal can be output so that different dielectric constants through different media, foams or adhesive substances can be differentiated in the control. This makes it possible to detect if a medium is polluted with another medium, e.g. oil polluted with water.

Figure 3: Supported by the FlexProgrammer, the CleverLevel series can perform even complex filling level detection tasks.

Assessment of measurement results and maintenance planning
The information that is visualized with the help of software can also be transferred to the higher-level controller. It can then evaluate the measuring signal. It ultimately knows if the position of the switching point shifts because another medium is in the tank during flushing, for example. Dirt in the tank can also be detected in this way and cleaning can be scheduled accordingly. Today, many application areas are dependent upon this information. Wind power plants are a typical example of this, because “spontaneous” maintenance of lubricant containers is extremely costly and can only be carried out at unjustifiable expense. The same applies to locomotives, ships or mobile implements in agriculture, for example.

A further strength of the level-monitoring sensor is particularly evident in mobile tanks. It normally works with a response time of 0.1 sec., which permits high-speed filling processes and the precise maintenance of filling levels. However, this becomes a disadvantage if the tank is in motion and the contents slosh around. In such cases, a switching delay of up to 10 sec. can be set to avoid false signals due to tank movement.

Figure 4: Using the Flex Programmer software, the switching range can be adjusted as required to ignore foam during maximum or minimum monitoring.

Robust, hygienic, with ATEX approval
But the new CleverLevel series offers even more. The level switches can be installed in any position, even in rather inaccessible locations. The LED that signals the switching process is highly visible in all directions. The sensor works silently, compliance with protection class IP67 requirements is standard, and it is suitable for ambient temperatures between -40°C und +200°C. Operation is also unaffected by vibrations. For example, the latter is important if the level switch is placed close to a pump as protection against dry running. The small penetration depth of only 15 mm is also a positive feature in these circumstances. Flow and pressure are hardly affected. In addition, thanks to gap-free installation and the smooth tip, nothing can adhere to the sensor.

In addition to the industrial process connections, there are also versions with EHEDG approval and an ATEX version for Ex areas for applications with stringent hygiene requirements. There are countless application possibilities for this all-rounder level switch. The food and beverage industry can benefit from its possibilities as much as every other industry, from pharmaceuticals, chemicals, petrochemicals, and process engineering all the way to the water supply and wastewater fields. Further areas of application are found in wind power plants, mobile machinery, cereal mills or cleaning facilities and pumping systems.

Figure 5: There are countless areas of application for this fill level sensor all-rounder, such as filling liquid chocolate.


Level detection of foaming media

12/08/2010

 

Accurate and repeatable point level measurement using electromagnetic waves

Thick & Creamy!

What coffee connoisseurs love about their latte macchiato is the thick, creamy milk froth on top of their drink. However, in many processes, frothing appears as an undesirable side effect that can lead to problems if it influences the level measurement. Ideally, the sensor would ignore the foaming, as it does with the level switch LFFS for point measurement, sensing using electromagnetic waves, which only reacts after the actual liquid level has been detected.

Foaming – a Challenge for Level Measurement

Although seen in many fields of daily life – just think of a hot bubbly bath or the tempting froth on fresh beer – foaming poses a challenge in process measurement, for example in the brewing, fruit juice or milk industries.  Point level detection in tanks is one of the most common applications in the process industry, making use of a number of point level switches based on various technologies. The technologies’ suitability depends on the application and external standards or approvals requirements. High hygienic standards have to be met especially in the pharmaceutical and food and beverage industries, where approvals like 3A, EHEDG and FDA certifying the devices’ hygienic capability regarding their design, construction and material, are essential.In many processes in these industries, the foam forming on the surface of the rising or falling liquid level would be detected by an ordinary level switch, which would operate even though actual liquid level had not yet been reached. Erroneous level measurements caused by false minimum or maximum level indications lead to process downtime or production quality problems.

Level switches by Baumer

Baumer's LFFS sensor

For applications like these, Baumer offers the LFFS designed especially for the use in hygienic processes. With its factory supplied configuration the level switch will detect the difference between foam and any aqueous liquid. Additionally, by using the configuration tool FlexProgrammer 9701, the adjustment of switching sensitivity, response time and output options, allow precise measurement parameters to be set. Prevention of erroneous level measurements using the LFFS allows productivity to be increased, quality improved and financial efficiencies realised.

An operating principle based on electromagnetic waves

A high-frequency signal sweep is radiated from the sensor tip into the tank. The media will act as a virtual capacitor, which together with a coil in the sensor head, forms a circuit creating the switch point signal. This virtual capacity will depend of the medium’s dielectric value and is well defined for most media. The switching function – whether open or closed – can be realised by changing the type of connection or by use of the FlexProgrammer 9701. The output type can be chosen as PNP, NPN or digital out by the programming unit. A damping of the output signal can be activated in case of a fluctuating media level, e.g. during the tank filling.

The advantage of the LFFS technology lies in the fact that only the very small conical measuring tip needs contact into the media. With other technologies the sensor requires a bigger surface contact into the media which viscous or adhesive media can easily adhere to causing switching errors. Whereas with the LFFS the small wetted surface of the sensor is highly resistant to media adhesion.

A special 3A welded socket ensures the hygiene-approved mounting into the process tank, and further offers the advantage of a drilled port to show leakage past the measuring tip that would consequently cause a dead-space contamination problem.

Welded socket with drilling

LFFS with cooling neck

The device’s 3A approval is only valid in conjunction with a 3A approved tank mounting connection – in this case a welded socket. All components in contact with the media to be measured are made of acid-proof high-quality steel or PEEK thermoplastics and fulfil the FDA, 3A and EHEDG regulations. The device is available with various 3A-approved process connections.

The LFFS measures the limit value of fluids (e.g. water, beer, milk); viscous and even dry substances (e.g. ashes, flour or grain). Already factory preset and without any further adjustment, the LFFS detects the level of aqueous fluids, liquids, viscous fluids and even dry media. For particularly difficult media like adhesive substances, the teach-in function enables a manual adjustment of the level switching point to be programmed.

A 360’ visible high intensity blue LED on top of the LFFS indicates when the switch point is reached, with the switching status user programmable to normally open (NO) or normally closed (NC). The indication can be seen easily even if the sensor is mounted on top of a tank. Operation is unaffected by vibration or turbulence in the media. Since the mounting position does not affect its performance, the sensor can be installed sideways or at the bottom of a pipe as used for pump dry-run protection.

For use in closed tanks the device withstands a pressure of up to 40 bar. Since the level switch does not contain any moveable parts and its electronic unit is completely integrated, it is maintenance-free offering a high reliability and low cost of ownership.

Crème Fraîche

Youghurt!

In the standard version, the level switch is designed for permanent process temperatures from  -40 °C up to +85 °C. However, it is suitable for the use in CIP and SIP facilities with short-term temperatures of up to 140 °C for a maximum of one hour. With an optional 100 mm or 250 mm cooling neck, the LFFS can then be used continuously at process temperatures of up to 200 °C. The cooling necks are designed with sliding connections and can therefore serve as an extension, e.g. if the sensor tip has to reach deeper into the tank, or if the media has to be reached through a tank insulation.

Applications in the food industry

The hygienic LFFS models are used primarily in the food and beverage industry. At Denmark’s largest yoghurt dairy, in Brabrand, Arla Foods uses the LFFS in the balance tanks of different filling machines for high and low level detection. In one case the medium is yoghurt, in the other it is Crème Fraîche, a heavy cream with 10 to 38 % fat content. Both media are very viscous and adhere to the measuring devices. Arla Foods has removed vibrating tuning fork type switches because their function and switching was affected when the media adhered to the forks which led to incorrect measurements. These were replaced with LFFS that now detect the level accurately and reliably.

Further principles of level measurement

In addition to the LFFS, Baumer offers their customers optimal solutions and technologies for most level measurement applications, utilising a wide range of continuous and point measuring level devices based on various technologies, including differential pressure; potentiometric; capacitive; ultrasonic and optical. These are variously available for contact or non-contact as well as side-view mounting.