TL;DR Summary
Accurate level control is critical for efficiency, product quality and safety in hygienic industries.
Food, beverage and life science manufacturers rely on precise level monitoring in storage and process containers to optimise resources and maintain compliance.
Hydrostatic, potentiometric and weighing systems each serve unique needs depending on tank type, medium and environment. Hydrostatic systems, like Anderson-Negele’s L3 Neo, offer high accuracy for liquids in diverse tanks, while potentiometric sensors excel with foaming or viscous media. Weighing systems provide reliable measurement for storage silos and interchangeable containers.
Selecting the right sensor involves considering accuracy, temperature drift, hygienic design and maintenance requirements. Advanced technologies such as hermetically sealed dual-diaphragm designs ensure consistent performance even in humid or outdoor environments, supporting cleaner, smarter, and more efficient processing.
Highly accurate continuous hygienic level control in all storage, balance or process containers is an essential requirement for maximum resource efficiency in every step of food, beverage and life science production.
The range of measurement systems, however, is as vast as it is confusing. Hydrostatic and potentiometric systems as well as weight measurement have proven particularly suitable for the requirements in hygienic applications. But which technology is the best for a specific medium, tank type, process or application?
Subscribe to PII and receive:
Our long-established bi-monthly digital magazine *Process Industry Informer*, featuring exclusive articles, news and updates across the Process Industries, plus commentary from our three industry experts:
Sean Moran
Gavin Smith
Dave Green
PLUS:
- Process Industry Update — our weekly e-newsletter
- PII Podcast
- Special messages from our advertising partners
A new Whitepaper “Hygienic, continuous level control technology – Overview and criteria for selection” can help finding the answer.
The suitability of hygienic level control methods for food or beverage production depends on a variety of factors, including tank type, process conditions and media properties. The most important are:
- Type, size, shape, material, and orientation (vertical / horizontal) of the container
- Required measurement accuracy
- Material properties of the media (liquid, pasty, adhesive, foaming, conductive/non-conductive, etc.)
- Media temperature and density, as well as their dynamic changes
- Changing media or consistent media in the process/tank
- Location (outdoor, indoor) and climatic requirements (condensation/humidity) for the instrumentation
- Pressure environment (atmospheric pressure or pressurised tank)
- Data output (indication on display, communication analog / digital)
- Installation, accessibility, and maintenance requirements (process connection / service life / repairability)
Hydrostatic Level Measurement
In this technology the fill level is measured by pressure transmitters at the bottom of the container, and displayed and/or output to the PLC. The instrumentation range extends from “simple” pressure transmitters to devices with additional functions integrated into the evaluation unit.
“Highly accurate continuous level monitoring in all storage, balance, or other process containers is an essential requirement for maximum resource efficiency in all process steps of the food, beverage and life science industries.”
In the top product range, such “smart” sensors already offer tank linearisation and density compensation in their electronics, as well as an integrated RTD temperature measurement element that captures the process temperature in real-time for the calculation of the specific density.
Such sensors can output measurements, with very high accuracy, in gallons, litres, kilograms or other volume units, even in dynamic temperature scenarios.
Another criterion for the precision of the level monitoring is the temperature drift. Conventional sensors can drift up to 0.4 % per 10 °C in such cases, while devices in the top-quality range offer a substantially reduced temperature drift of just 0.03 % per 10 °C, providing significantly higher precision with a basic accuracy of only 0.1 %.
Before choosing a device you should define the accuracy of your device that you need in your process and evaluate the sensor offerings accordingly.
The classic application of hydrostatic hygienic level measurement is large containers such as product receiving, storage, or mixing tanks.
Thanks to exceptional performance characteristics and measurement accuracy, “smart” sensors like the L3 Neo with their highly accurate level measurement are also suitable for smaller balance or process tanks, for which hydrostatic sensors were previously considered not precise enough.
This significantly expands the application range of this easy-to-install, reliable, low-maintenance, and hygienic measurement technology:
- All types of liquids such as product, CIP media, water, regardless of conductivity, viscosity, density, etc.
- Vertical and horizontal tanks, regardless of height, volume, or shape
- Tanks indoors or outdoors, even in very humid environments
- Also for changing media with different densities
- Pressurised tanks such as fermenters (differential pressure detection)
- Rapid level changes such as during filling
- Non-metallic tanks
Challenge: Condensate in damp and cold environments or in outdoor tanks
Due to condensation, problems such as drifting or unstable measurements can occur, particularly in humid environments or with outdoor storage containers. For relative pressure measuring cells with compensation capillaries, a thin tube leads the atmospheric pressure from the environment to the back of the measuring diaphragm.
For sensors with diffusion-open double diaphragms, a separate pressure diaphragm is used for atmospheric pressure and hydrostatic pressure. Both methods have a fundamental disadvantage: the diffusion of water vapour cannot be permanently prevented. Condensing water vapor can cause sensor drift or fluctuating measurement values.
This problem can be overcome with a specific “dual-diaphragm”-technology, where atmospheric pressure is detected through a second, hydraulically connected measuring cell. This hermetically sealed measuring system with dual-diaphragm design and atmospheric reference measured with a hygienic, un-clogable diaphragm makes it impossible for gases and moisture to enter, ensuring consistently precise measurement values and makes drift problems reliably a thing of the past.
Potentiometric Level Measurement
The potentiometric measurement principle works with the detection of the change in voltage ratio in the sensor’s measuring rod, which extends into the liquid. Depending on the type, installation from above, below, diagonally, and, with a bent measuring rod, also in the side wall of a tank is possible.
The length and the shape can be precisely matched to the container. Modern measurement methods determine the immersion state of the electrode rod in the medium and ensure that incorrect measurements due to adhesions and foam are avoided.
This technology is limited to vessel sizes covered by the maximum rod length of the sensor, but in those cases it offers a whole range of advantages compared to hydrostatic level control. Due to its insensitivity to foam and adhesions, high measurement accuracy and short response time, potentiometric sensors are ideal for hygienic level control in a variety of food and beverage processing applications, such as:
- All conductive liquids such as product, CIP media, water, etc.
- Applications such as balance tanks in pasteurisers, heaters, coolers, filling systems, carbonators, separators, horizontal tanks, etc.
- Strongly or variably foaming media
- Pasty or adhesive media such as syrups, ice cream, sauces, etc.
- Pressurised tanks
- Rapid level changes such as filling applications
- Non-metallic tanks
- Different media in one tank (automatic adjustment to changing media)
Inventory control through weighing systems
Content monitoring by weight measurement is particularly suitable for storage silos, both for dry goods and liquids, as well as for all types of interchangeable containers. Two systems are available: substructure load discs that are mounted under the container feet, bolt-on load cells are screwed onto the leg construction.
“Due to its insensitivity to foam and adhesions, high measurement accuracy and short response time, potentiometric sensors are ideal for hygienic level control in a variety of food and beverage processing applications.”
Load Disc weigh systems are designed to measure the contents of process or storage containers dynamically and with high accuracy, detecting even the slightest weight changes. They are mounted between the container‘s feet and the foundation, and should provide a low profile ensuring stability and resistance to tipping.
They can compensate for lateral forces caused by stirring systems. Many devices come with a compact, hygienic design with polished surfaces and high protection class makes them easy to clean and suitable for use in food, beverage, and pharmaceutical applications.
Bolt-on load cells are compact and reliable strain gauge sensors designed for the cost-effective and safe measurement of quantities in all types of metal-supported containers with a total load of more than 35 tons.
They eliminate measurement inaccuracies caused by angle of repose, bridging, moisture content, or compaction. The sensors are simply screwed onto the metal feet (bolt-on). Integrated strain gauges detect changes in the metal caused by even the slightest changes in the container contents and transmit them as measurement signals to the controller.
Additional Selection Criteria
In addition to the measurement technology itself, other parameters must be considered when selecting a hygienic level control systems, such as the hygienic design of the sensor and process connection, lifespan of components, resistance to chemical or mechanical stress, base measurement accuracy and the influence of temperature drift, installation environment and climatic requirements, data transmission (analog/digital), ease of use, accessibility of the display, etc.
New Whitepaper
In a whitepaper titled “Hygienic, Continuous Level Measurement Technology – Overview and Selection Criteria,” the sensor specialist Anderson-Negele has outlined selection criteria, suitability for applications, and product overviews. For more information, download here
FAQs
Why is level control important in hygienic applications?
Accurate level measurement ensures process efficiency, product quality and regulatory compliance in food, beverage and life science production.
What types of level measurement technologies are used?
Common options include hydrostatic, potentiometric and weighing systems, each suited to specific media and process conditions.
When should hydrostatic level sensors be used?
They are ideal for large or pressurised tanks and can handle liquids of different viscosities and densities with high precision.
What makes potentiometric measurement effective?
It offers fast, accurate readings and is resistant to foam and adhesions, making it ideal for pasty or foamy media.
How do weighing systems help with inventory control?
Weighing sensors accurately monitor contents in silos or containers regardless of product type or moisture levels.
What factors should be considered when choosing a level sensor?
Consider hygienic design, measurement accuracy, temperature stability, installation requirements and communication interface.
