How to avoid interference from radiation sources when measuring resistance temperature (RTD)? These methods are very practical.

In industrial temperature measurement, resistance temperature detectors (RTDs) are the most commonly used temperature sensing elements in the medium and low temperature range, and their measurement accuracy directly affects production safety and product quality. However, in practical applications, radiation sources outside the measured temperature field often interfere with the measurement results. Today, we will discuss how to effectively avoid this type of interference and ensure accurate and reliable temperature measurements.

When there are high-temperature objects around the RTD, such as furnace walls, heating elements, or other thermal equipment, these radiation sources will emit radiant heat towards the RTD. If there is a temperature difference between the RTD and these radiation sources, even if the temperature of the measured medium does not change, the RTD will still experience measurement errors due to receiving additional radiant energy. This situation is particularly common in industrial furnaces and high-temperature pipelines.

Practical Methods to Effectively Avoid Radiant Heat Interference

1. Install a Radiation Shield

Installing a radiation shield between the RTD and the radiation source is a direct and effective method to eliminate radiant heat interference. The radiation shield can effectively block the direct radiation propagation path between the radiation source and the RTD. In practice, the radiation shield should be installed between the RTD and the radiation source, and its surface should be smooth to reduce the emissivity and its own radiation capacity. This method is simple, easy to implement, and low-cost, and can be quickly implemented in various industrial scenarios.

2. Increase the wall temperature and reduce temperature difference

The magnitude of radiative heat interference is closely related to the temperature difference between the RTD and the radiation source. By reducing this temperature difference, the impact of radiative heat can be significantly reduced. Specifically, a layer of insulation material can be wrapped around the surface of the container wall to increase the wall temperature, thereby reducing heat loss. This method not only reduces radiative interference but also improves energy efficiency.

3. Optimize the installation location and method of the RTD

Proper installation is a fundamental measure to avoid radiative interference. The RTD should be installed vertically as much as possible to avoid direct contact with the furnace wall. The wiring outlet of the junction box should face downwards to prevent moisture and dust from falling in. When choosing an installation location, obvious radiation sources such as flames and high-temperature furnace walls should be avoided. If this cannot be avoided, a suspended installation can be considered, with insulation material used to isolate the RTD from the support.

During installation, it is also important to note that the insertion depth of the RTD should be at least 8-10 times the diameter of the protective tube to ensure that the measuring end is close to the true temperature of the object being measured.

4. Increase Medium Flow Rate to Improve Convective Heat Transfer

Increasing the flow rate of the measured medium enhances convective heat transfer between the RTD and the measured medium, thereby reducing the influence of radiative heat. This is because the convective heat transfer coefficient increases with flow rate, causing the RTD to exchange heat with the medium more through convection rather than radiation. However, it should be noted that there are limits to the increase in flow rate; typically, the maximum flow rate should be below 80 m/s.

5. Select a Suitable RTD Protection Tube

The characteristics of the protection tube also affect its resistance to radiation interference. Reducing the outer diameter of the protection tube and selecting a material with a low emissivity can effectively reduce the influence of radiative heat. Generally speaking, protection tubes with smooth surfaces and low emissivity have a weaker ability to absorb radiative heat, which is beneficial for reducing radiation errors.

Comprehensive Protection Strategies for Special Environments

In high-temperature and high-pressure environments, outdoor RTDs installed at high altitudes require waterproofing of the sheathing and leads, as well as proper insulation of the leads. If the RTD (Resistance Temperature Detector) is to be immersed in oil for extended periods, oil- and heat-resistant polytetrafluoroethylene (FEP) insulated cables should be selected. This material can be used continuously within a temperature range of -250 to 250°C and possesses excellent oil resistance, corrosion resistance, and heat resistance.

In environments with strong vibrations, protective devices should be installed at the junction of the cable lead-in and the RTD, such as tapered spring protective tubes, corrugated tubes, and armored wire extension protection, to prevent wire breakage at the root.

Hequan Instrument Technology Co., Ltd.'s Temperature Measurement Solutions

Facing the challenges of temperature measurement in complex industrial environments, Suzhou Hequan Instrument Technology Co., Ltd., with nearly 22 years of experience in the temperature control industry, provides professional solutions for its customers. Hequan Instrument develops and manufactures high-precision temperature control products tailored to the specific needs of different industries, enabling precise temperature control, ensuring stable production processes, and improving product quality and production efficiency.

Its temperature sensors boast an accuracy of up to 0.1 degrees Celsius, long service life, and fast response speed, enabling real-time and accurate monitoring of production equipment temperature. To address issues of radiation and electromagnetic interference, Hequan Instruments' temperature sensors employ high-quality shielding materials and a scientific grounding design, effectively resisting external interference and ensuring measurement accuracy in complex industrial environments.

Whether it's the radiant heat environment of high-temperature furnaces, the strong magnetic field scenarios of hydropower plants, or the high-precision temperature control requirements of blow molding machines, Hequan Instruments can provide customized solutions. The company has served over 10,000 industrial equipment users and provided supporting products and services to numerous Fortune 500 companies.

In today's increasingly automated industrial environment, accurate temperature measurement has become a crucial link in ensuring production safety and product quality. Through the aforementioned scientific installation methods and effective protective measures, combined with professional temperature control products like those from Hequan Instruments, we can ensure that RTDs operate stably in various complex environments, providing reliable data support for industrial production.