Precise temperature monitoring is the foundation of reliable operation for any heating, hydraulic, or industrial installation. At Onninen, we know from years of experience that bimetallic thermometers are one of the most universal and reliable ways to control thermal parameters in various technical applications.
These mechanical measuring devices, based on the physical phenomenon of different thermal expansion of metals, are used wherever durable and independent temperature control is required - from simple heating installations, through air conditioning systems, to advanced industrial processes. Our range includes a wide variety of solutions from renowned manufacturers such as AFRISO and WIKA.
Thanks to their simple mechanical construction, bimetallic thermometers do not require electrical power, making them ideal for operation in harsh environmental conditions where reliability is of utmost importance.
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Principle of operation of bimetallic thermometers in installation practice
Bimetallic thermometers utilize a fundamental law of physics - the different thermal expansion of metals. At the heart of each such device is a bimetallic element made up of two different metal strips, permanently bonded together. Each of these metals has a different coefficient of thermal expansion, which means they react to temperature changes to varying degrees.
Precision measurement mechanism
As the temperature rises, one of the metals expands significantly more than the other, causing mechanical deformation of the bimetallic strip. This deformation can take a spiral or helical form, depending on the design of the specific model. The resulting rotational movement is then transmitted through a gear system to the thermometer's pointer, allowing for precise temperature readings on a clear dial.
Measurement range and accuracy
At Onninen, you will find bimetallic thermometers with various measurement ranges - from low-temperature models (-70°C to +200°C) to high-temperature ones (up to +600°C). Accuracy class 1 or 2 according to EN 13190 ensures precise measurements, and various dial diameters (from 63 mm to 160 mm) allow for the device to be tailored to the specific requirements of the installation.
| Parameter | Range/Value | Application |
|---|---|---|
| Operating temperature | -70°C to +600°C | Universal installations |
| Dial diameters | 63, 80, 100, 160 mm | Various mounting points |
| Accuracy class | 1 or 2 (EN 13190) | Precise measurements |
| Length of the sleeve | 40-300 mm | Deep immersion |
Practical applications in various types of installations
Heating and central heating installations
In central heating systems, bimetallic thermometers play a key role in monitoring temperature at critical points in the circuit. They are installed at the boiler outlets, at main distributors, and on the return of the installation. This allows installers to continuously monitor the efficiency of the system and detect potential problems, such as decreased performance or incorrect flow of the heating medium.
Ventilation and air conditioning systems
In HVAC installations, we offer special models with a sliding flange, ideal for installation in air ducts. These devices allow for precise monitoring of air temperature in different zones of the building, which is crucial for maintaining optimal comfort conditions with minimal energy consumption.
Industrial installations
In industrial environments, where harsh operating conditions prevail, we recommend industrial thermometers made of stainless steel from our offer. They are characterized by increased resistance to corrosion, vibrations, and extreme temperatures. Additionally, models with oil filling are available, which dampen vibrations and provide stable readings in applications with high mechanical loads.
- Tanks and silos - monitoring the temperature of stored media
- Technological pipelines - control of the temperature of transported substances
- Industrial furnaces - monitoring high-temperature processes
- Cooling systems - control of temperature in cooling circuits
Advantages of bimetallic thermometers over other solutions
Our experience in the installation industry shows that bimetallic thermometers offer unique advantages that are hard to find in other types of measuring devices. Above all, their mechanical construction ensures independence from electrical power - a feature particularly valuable in locations without access to energy or in explosion-hazard zones.
Durability and reliability
Thanks to their simple mechanical construction, the products from our offer are characterized by exceptional durability. The absence of electronic components means resistance to electromagnetic interference, moisture, or extreme temperature conditions. In practical installation, this translates to years of trouble-free operation without the need for maintenance or battery replacement.
Cost-effectiveness
Compared to electronic temperature sensors, bimetallic thermometers offer an excellent quality-to-price ratio. The lack of operating costs associated with power supply or component replacement means that the total cost of ownership is significantly lower than with alternative solutions.
Versatility of installation
In Onninen's range, models with various types of process connections - rear, bottom, radial, and with a mounting strap - are available. This variety allows for optimal adaptation to the specifics of each installation, regardless of spatial constraints or technical requirements.
Selection of technical parameters for specific applications
Dial diameter and readability of readings
The choice of the thermometer's dial diameter should take into account the installation conditions and readability requirements. Models with a diameter of 63 mm work well in tight boiler room spaces, while larger dials of 100-160 mm are ideal for installation in visible places where readings are required from a greater distance.
Length of the immersion sleeve
A key parameter is the length of the sleeve, which determines the depth of immersion of the sensor in the measuring medium. Standard lengths in our offer are:
- 40-45 mm - heating installations with standard pipe diameters
- 63-68 mm - larger pipelines and collectors
- 100-300 mm - tanks, silos, and industrial applications
Construction materials
We offer thermometers in various material versions, tailored to the specifics of the measuring medium:
- Galvanized steel housing - standard applications in heating installations
- Stainless steel - aggressive environments, food industry
- DZR brass - water installations, resistance to dezincification
Frequently asked questions
1. What is the optimal measurement range for a heating installation?
For standard central heating installations, we recommend a range of 0-120°C, which covers typical operating temperatures of the heating system with an appropriate margin. In our offer, the most commonly chosen solutions are models with a range of 0-120°C or 0-160°C, which provide precise indications in the operating range of 40-80°C.
2. Do bimetallic thermometers require calibration?
Bimetallic thermometers from our offer are factory calibrated according to EN 13190 and do not require additional calibration. Their stability of indications results from the mechanical construction, which does not undergo drift characteristic of electronic devices. Accuracy class 1 or 2 is maintained throughout the entire period of operation.
3. When should thermometers with oil filling be used?
Oil filling is recommended in applications with high vibrations and for operating temperatures up to 250°C. Silicone oil dampens the pointer's oscillations and provides stable readings in harsh industrial conditions. This solution works well in pumping stations, near compressors, and in installations with intense medium flow.
How often should a bimetallic thermometer be replaced?
Bimetallic thermometers have a very long lifespan - typically 10-15 years under standard operating conditions. Replacement is only necessary in the case of mechanical damage, jamming of the pointer, or significant deterioration of the dial's readability. In our experience, with proper installation and operation, these devices serve without problems for decades.
4. Which construction materials should be chosen for water installations?
For water installations, we recommend models with a sensor and housing made of stainless steel or dezincification-resistant brass (DZR). These materials provide long-lasting resistance to corrosion in contact with drinking and technical water. In Onninen's offer, you will also find models with PZH certification for use in drinking water installations.
5. What is the difference between rear and bottom connections?
The rear (axial) connection allows for easier installation in horizontal pipelines, while the bottom (radial) connection works well in vertical installations and tanks. In practical installation, the choice depends on the available space and the direction of the pipes. Both types offer identical measurement accuracy.
Professional solutions for demanding installations
At Onninen, we understand that every installation presents unique requirements for the temperature monitoring system. Therefore, our range of measuring devices includes not only standard thermometers but also advanced specialized solutions.
As a market leader in the installation industry, we work directly with renowned manufacturers, allowing us to offer top-quality products at competitive prices. Our team of technical specialists provides advice on selecting optimal solutions, taking into account the specifics of the particular installation and operational requirements.
We offer comprehensive solutions for installation technology, which include not only the measuring devices themselves but also a full range of mounting accessories, protective thermometer covers, and auxiliary elements. With a wide network of branches across the country, we ensure quick availability of products and professional technical support at every stage of project implementation.
Bimetallic thermometers are an investment in long-term reliability and precision in temperature monitoring. By choosing products from Onninen's offer, you gain assurance of quality, support from experienced specialists, and a guarantee of access to the most modern technical solutions in the installation industry.