Hall Sensors as Mini Level Sensor

What Characterises Hall Sensors as Mini Level Sensor?

Continuous level measurement places high demands on installation space, signal quality and mechanical robustness. Especially in compact containers or mobile applications, robust and precise measurement systems are required that can be reliably integrated into existing industrial infrastructure.

With the introduction of a Hall-based measurement chain in the Mini Level Sensor, Reed Electronics AG is specifically expanding its portfolio for these demanding applications. The new solution complements the proven Reed-based variants and offers a solid-state alternative for applications where increased vibration resistance, defined switching points and low sensitivity variation are key requirements.

Developed in collaboration with an international semiconductor manufacturer and based on automotive-proven technology, the Hall variant has been consistently designed for industrial requirements. It combines the compact design of the Mini Transmitter with an active sensor technology that generates a defined electrical output signal and can be integrated as standard into 4 to 20 mA systems.

This creates an additional option within the existing product portfolio without replacing the established strengths of classical Reed technology. Instead, the Hall-based measurement chain expands the application possibilities of the Mini Transmitter in cases where mechanical robustness, temperature stability and reproducible switching behaviour are particularly critical.

Initial Situation and Requirements in Level Measurement

Continuous level measurement in compact containers presents several challenges for developers and operators. The available installation space is often highly limited, while measurement values must remain stable, reproducible and reliably transmitted over long periods. This is particularly relevant for analytical devices, industrial modules, mobile systems or applications in chemically demanding environments.

In addition to space constraints, mechanical stress plays a central role. Vibrations, shocks or changing installation positions can affect switching behaviour. Temperature fluctuations also impact magnetic systems and electronic components. A level measurement solution must therefore be both mechanically robust and temperature-resistant.

Another decisive factor is signal processing. In industrial systems, a 4 to 20 mA current interface is commonly used. This signal format is considered robust against electromagnetic interference and is suitable for longer transmission distances. The sensor technology must therefore not only be mechanically stable but also electrically compatible with existing systems.

At the same time, requirements vary depending on the medium, tank geometry and installation situation. Small containers, narrow guide tubes and small float diameters require particularly compact sensor concepts with fine resolution and precisely defined switching points.

Against this background, further development of the Mini Level Sensor was a logical step. The goal was to complement the existing design with a technology that enables even more stable and reproducible signal generation under increased mechanical stress and tight tolerances.

Starting Point Within the Reed Electronics AG Portfolio

The Mini Level Sensor is positioned within our product portfolio as a particularly compact solution for continuous level measurement. Its design with a small tube diameter and reduced float diameter allows use in narrow containers and applications with limited installation space. Depending on the version, different output signals can be realised, including resistance, 0 to 10 V and 4 to 20 mA.

In its classic version, the Mini Level Sensor is based on a plastic-encapsulated Reed switch measurement chain. A Reed switch is a passive electromechanical component that is actuated by a magnetic field and does not require an additional power supply. This technology is characterised by simple integration, clearly defined switching points and the possibility of Ex designs.

For many applications, this design remains the preferred solution. Especially where passive signal generation without external power supply is required or where individual defined switching points are the main focus, Reed technology offers clear advantages.

At the same time, certain applications have shown that under increased mechanical stress, high vibration requirements or particularly tight tolerance specifications, an alternative sensor technology can provide additional stability and reproducibility. Against this background, the decision was made to expand the existing Mini concept technologically without replacing the proven Reed variant.

The Solution: Hall-Based Measurement Chain in Mini Format

With the introduction of a Hall-based measurement chain, we expand the Mini Level Sensor with an active sensor technology. The goal was to maintain the compact design while enabling higher mechanical robustness and more precise signal generation.

In contrast to the Reed switch, a Hall sensor is an active electronic semiconductor component. It requires a power supply and generates a defined electrical output signal. The switching signal is created by evaluating the Hall effect, i.e. the change in voltage in a conductor or semiconductor when exposed to a magnetic field. No mechanical contacts are required.

Depending on the application, the Hall sensors can additionally be protected with a 2K potting compound. This potting increases vibration resistance and improves protection against environmental influences, but is not mandatory for every design.

Technological Approach and Design Principle

The Hall-based version of the Mini Level Sensor follows the same basic mechanical principle as the classic variant: a float with an integrated permanent magnet moves along a guide tube according to the level of the medium. The difference lies in the method of signal detection.

Instead of mechanical contacts, Hall sensors are positioned along the tube. These detect the magnetic field of the float without contact and convert the magnetic field change into an electrical signal.

By eliminating mechanical switching contacts, a fully electronic, contactless measurement chain is created. This reduces mechanically induced wear mechanisms and minimises sensitivity to vibrations or shocks.

Another technical aspect is the defined magnetic sensitivity of the Hall sensors. This can be matched to the applied magnetic system. This enables reproducible switching points and a uniform resolution within the measurement chain.

The basic functional principle can be summarised as follows:

• The Float Contains a Precisely Defined Permanent Magnet.
• Hall Sensors Are Arranged Along the Guide Tube in a Fixed Pitch, Typically 5 mm.
• As the Float Moves, the Magnetic Field Changes at the Respective Sensor Position.
• The Hall Sensor Detects This Change and Outputs a Defined Electrical Signal.
• The Evaluation Electronics Converts This into a Standardised Output Signal, for Example 4 to 20 mA.

Signal Processing and Integration into 4 to 20 mA Systems

In industrial applications, the 4 to 20 mA current interface has become an established standard for analogue process signals. The current signal is relatively insensitive to electromagnetic interference and enables stable signal transmission even over longer distances. In addition, a cable break can be clearly detected, as currents below 4 mA are interpreted as a fault condition.

The Hall-based measurement chain of the Mini Level Sensor is designed as standard for this interface. The individual Hall sensors detect the position of the magnetic float in defined steps. An integrated evaluation electronics processes these signals and generates a standardised current signal in the range of 4 to 20 mA, proportional to the level. This ensures predictable and system-compatible integration into existing systems.

Depending on the application, alternative output signals can also be implemented. However, the 4 to 20 mA variant provides a robust and standardised solution for continuous level monitoring, especially in demanding industrial environments.

Where Reed Switches Remain the Right Choice

Despite the Extension with a Hall-Based Measurement Chain, Reed Technology Remains a Core Part of Our Portfolio. In Many Applications, the Reed Switch Offers Design and Functional Advantages That Cannot Be Replaced by Active Sensor Technologies.

A Reed Switch Is a Passive, Magnetically Actuated Switching Element. It Does Not Require Its Own Power Supply and Generates Its Switching Signal Exclusively Through the Applied Magnetic Field. This Property Is Particularly Relevant Where Simple, Energy-Independent Solutions Are Required.

Reed Technology Is Also Characterised by Clear Switching Behaviour and a Design That Has Been Proven for Decades. In Many Standard Industrial Applications, It Fully Meets the Requirements in a Reliable and Cost-Effective Way.

Typical Use Cases Where Reed Switches Remain Suitable:

• Applications Without Available Power Supply for Active Sensor Technology
• Single Defined Switching Points Instead of Continuous Measurement
• ATEX or Ex Areas Where Passive Solutions Offer Design Advantages
• Systems with Very Simple Electrical Integration, for Example as a Pure Limit Switch Contact

Customisation Options with the Hall Mini Level Sensor

The Mini Transmitter Is Designed as a Modular System. This Allows Both the Classic Reed Version and the Hall-Based Version to Be Adapted to Specific Application Requirements. The Goal Is to Accurately Reflect Different Tank Geometries, Media and Installation Situations.

A Key Design Feature Is the Defined Measurement Pitch. As Standard, a Step Resolution of 5 mm Is Implemented. Deviating Pitch Distances Can Be Realised on a Project-Specific Basis if Required by the Application. This Allows the Desired Resolution to Be Adapted to the Volume, Container Shape or Control Strategy.

The Mechanical Design Is Also Flexible. Depending on the Medium and Environmental Conditions, Different Materials Are Available for the Tube, Float and Housing. Optional Additional Protection Measures Are Also Possible.

Furthermore, Combinations with Temperature Sensors Such as PT100 or PT1000 Are Possible. This Allows Level and Temperature Information to Be Combined Within a Single Sensor Unit.

This Modular Approach Creates a Flexible Platform Suitable for Both Standard Applications and Custom Sensor Concepts. The Hall-Based Measurement Chain Extends This System with an Additional Technology Option for Particularly Demanding Operating Conditions.

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