High-Temperature Sensors for Level Detection in Hot Media

Reliable Level Measurement at Temperatures up to 200 °C

Whether for minimum level detection in an oil tank or continuous level monitoring in a process: We develop and manufacture custom high-temperature sensors for hot liquids. Depending on the design and configuration, our standard range extends up to a maximum of 200 °C. Materials, floats and the electrical design are tailored to your application.

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Our High-Temperature Sensors: the Right Solution for Your Application

Do you need a signal when a specific liquid level is reached or continuous level indication? This distinction determines the appropriate sensor design. We also offer magnetic switches for position detection in hot environments. The following temperature limits apply to the respective high-temperature versions designed accordingly.

RCS Float Switches: Monitoring Limit Levels up to 200 °C

Our customised RCS float switches detect when a liquid reaches a defined level. They provide switching signals to the system control, for example for min./max. signals, dry-run protection or overfill monitoring. We adapt switching points, installation length and connections to your requirements.

For applications up to 200 °C, we use suitable stainless-steel components and reed switches that have been proven and tested for this temperature range. The RCS is therefore particularly suitable for applications in which individual limit levels need to be monitored reliably.

RCK MWG Transmitter: Continuous Level Measurement up to 150 °C

The RCK MWG transmitter measures the liquid level along a defined measuring range. This provides you with information for continuous level indication, process monitoring or automatic level control.

For further processing, 4–20 mA or 0–10 V are available. We select the measuring grid to suit the application, with 5, 10 or 15 mm. It describes the increments of the level detection and should not be equated with guaranteed measurement accuracy.

In the high-temperature version, the RCK MWG reaches up to 150 °C. With this compact design and miniaturised components, this is the temperature limit.

RCK MMWG Mini Transmitter: Compact Level Measurement up to 150 °C

Our RCK MMWG mini transmitter is designed for small tanks and confined spaces. With a tube diameter of 8 mm, it is our smallest design for continuous level measurement. The measuring grid is 5 mm; output signals of 4–20 mA or 0–10 V are also possible here.

The correspondingly designed high-temperature version can be used up to 150 °C. When planning the installation, we take into account not only the slim tube but also the space required for the appropriate stainless-steel float.

RCM Magnetic Switches: Position Detection at High Temperatures up to 200 °C

For non-contact proximity and position detection, we manufacture customised RCM magnetic switches in temperature-resistant versions up to 200 °C. A matched magnet actuates the reed contact and enables, for example, feedback on the position of a component or flap.

Housing, switching function and connection are configured to suit the installation situation. We match the appropriate actuating magnet to the switch and the operating conditions.

How Level Detection Works with the Reed Principle

A float with an integrated magnet follows the liquid level. Its magnetic field actuates the protected reed contacts inside the guide tube. In a float switch, this generates a switching signal at a defined height. A conventional reed transmitter, by contrast, detects the float position using a chain of reed contacts and resistors, enabling a level value to be output.

The float is the only moving component in the medium. The magnetic transmission does not require any mechanical connection through the tube wall to the internal electrical assembly. This simple operating principle forms the basis for a robust and durable sensor solution.

For compact high-temperature transmitters, we also consider Hall technology. In this case, semiconductor sensors detect the magnetic field of the float. Temperature-resistant, robust components from the automotive sector can be a suitable alternative for this purpose. Whether reed chain or Hall sensor technology: we select the technology based on temperature, design and measurement task.

Designed for High Temperatures: Stainless Steel, Cables and Internal Assembly

A heat-resistant level sensor consists of more than just a temperature-resistant measuring tube. The key is that all components are suitable for the load at their respective point of use: from the float and connection cable to the potting compound and electronics.

For parts in contact with the medium, we use V4A stainless steel in the upper temperature range, in particular 1.4435 and 1.4571. The E27Z, E44Z and E52 stainless-steel floats are suitable for this purpose. This allows both compact and larger designs to be implemented. Plastic floats made of PVC, PP or PVDF are reserved for applications with correspondingly lower temperatures.

The following ranges for our intended versions serve as a guide for material selection:

These values do not replace temperature approval for the complete sensor. In addition, the material must be chemically resistant to the respective medium.

Depending on the design, different cables are available for temperature-stressed connections. FEP cables and silicone cables are available for temperature ranges from −60 to +180 °C; for particularly high requirements, FEP-TE wires with a specified range from −100 to +205 °C can be used. We select the connection cable according to the actual temperature load and the other requirements of the application. The temperature resistance of individual components does not constitute approval of the complete sensor for this temperature range. Depending on the design, our high-temperature sensors have a maximum operating temperature of 200 °C.

For applications from 100 °C, the internal assembly is also designed to suit the temperature. Depending on the design, suitable high-temperature potting compounds or alternatively a sand filling inside are used. PCB materials and electronic components are likewise selected according to the thermal load. A standard FR4 solution is not used unchanged for the high-temperature range.

EX Versions and IP Protection Ratings

For potentially explosive atmospheres, our RCS float switches and RCK transmitters in EX versions are available. The design and assessment of the intrinsically safe RCS-EX and RCK-EX versions are based on the requirements of EN IEC 60079-0:2018, EN 60079-11:2012 and are marked Ex ia IIC T6…T4 Ga and Ex ib IIIC Ta Db. The marking Ex ia … Ga permits use in gas atmospheres up to and including Zone 0. The marking Ex ib … Db applies to dust atmospheres outside the tank up to and including Zone 21.

Separate temperature limits apply to the EX versions, which are below the maximum temperature ranges of our general high-temperature sensors: The documented liquid and ambient temperature range Ta extends from −20 to +80 °C and optionally up to +125 °C.

Documentation

The permissible intrinsic safety depends on the temperature class as well as the liquid and ambient temperature Ta:

Intrinsic Safety Data Ex ia IIC T6 Ga

Intrinsic Safety Data Ex ia IIC T4 Ga

The specific design must always be matched to the operating conditions and the marking of the respective sensor.

Depending on the design, connection and configuration, protection ratings up to IP68 can also be achieved. This applies, among others, to the customised RCS float switches, RCK transmitters and RCM magnetic switches.

Monitoring Level and Temperature in One Device

If required, we combine level detection with a PT100, PT1000 or temperature switch. PT100 and PT1000 enable temperature measurement, while a temperature switch provides a switching signal when a defined temperature limit is reached. This means your control system receives temperature information in addition to the level information.

This combination can eliminate the need for separate sensors and additional tank connections. The measuring position, connection and permissible temperature range of the additional function are coordinated with the overall sensor design.

Typical Applications: Hot Process Media, Oil Systems and Cleaning Processes

Depending on the medium, temperature and measurement task, our high-temperature sensors are suitable for various applications:

• Process, chemical and electroplating systems: Detect limit levels or continuous fill levels in heated process tanks. Resistance to the liquid and its concentration is just as important as temperature resistance.
• Oil and hydraulic systems: Monitor the liquid supply in hot oil tanks, signal a minimum fill level or provide measured values for demand-based refilling.
• Hot-water and cleaning processes: Detect the fill levels of hot water, cleaning liquids or condensate. For CIP processes, we also take changing media and temperature peaks during cleaning into account.
• Furnaces and drying systems: Use RCM magnetic switches to detect positions in thermally stressed areas of a system, for example the position of moving components.

For pressurised hot-water or steam systems, the pressure limits of the specific version also apply. RCS and RCK devices must not perform safety-relevant limiting or switching functions in pressurised applications.

Your Custom High-Temperature Sensor: Tailored to the Medium and Installation Situation

To determine the right design, we consider your application as a whole. This includes the medium with its composition and density, the operating and cleaning temperatures including possible peaks, as well as the operating pressure. The tank geometry, installation position, available opening and required sensor length are equally important. Switching points or measuring range, output signal and connection design complete the requirements.

The float must be able to move freely during operation. Heavily contaminated liquids, coarse particles and media prone to crystallisation are not intended for these designs. The temperature and pressure specifications of the specific version in the data sheet or on the nameplate remain decisive for use.

Send us your requirements for level detection in hot media. We will advise you on the appropriate design and tailor the materials, float and electrical assembly to your process.