Separated Type IR Pyrometers | SIMTRUM Photonics Store

Unlike the "direct signal processing within the probe" of integrated devices, the separated main unit can be far away from harsh environments such as high temperatures, dust, and vibration. It precisely amplifies, filters, linearly corrects, and performs data operations on electrical signals, and finally outputs the temperature value through the display screen. It simultaneously supports analog (4-20mA), digital (RS485/Modbus) and other signal outputs, facilitating integration into industrial control systems (such as DCS, PLC) for automated monitoring.

The core advantages of this equipment are mainly reflected in its environmental adaptability and application flexibility: On the one hand, the temperature measurement probe can be designed with high-temperature resistant materials and directly installed in areas near heat sources such as kilns, smelting furnaces, and high-temperature pipelines, while the main unit can be installed in normal temperature and low-interference environments such as control rooms and operation rooms. This not only ensures the temperature measurement accuracy of the probe but also extends the service life of the core components of the main unit. On the other hand, the separation distance between the probe and the main unit can be flexibly adjusted according to the demand, which can cover the "long-distance and high-risk" temperature measurement scenarios that are difficult for integrated equipment to reach, such as temperature measurement in the furnace of large thermal power generation units, surface temperature monitoring of steel continuous casting molds, and high-temperature area inspection of chemical reaction vessels.

Basic composition

The structure of the IR pyrometer is designed around the logic of "capturing radiation - converting signals - processing and calculating - outputting results", and its core components include four major modules:

• Optical system: It is equivalent to an "infrared signal collector", composed of components such as lenses, mirrors or optical fibers. Its function is to converge the infrared light radiated by the object under test and focus it on the subsequent infrared detector, reducing the interference of ambient stray light and enhancing the signal strength.
• Infrared detector: The core sensing component, responsible for converting the infrared radiation energy gathered by the optical system into measurable electrical signals.
• Signal processing circuit: The electrical signals output by infrared detectors are usually weak and noisy. This module enhances, denoising, and digitizes the signals through amplification circuits, filtering circuits, A/D conversion circuits, etc. At the same time, it incorporates algorithms such as environmental temperature correction to eliminate the influence of external factors on the measurement.
• Display and Output unit: Responsible for presenting measurement results and achieving signal interaction.

Working principle

The separated IR pyrometer continues the core logic of infrared temperature measurement - relying on Planck's blackbody radiation law, it senses the IR radiation energy emitted by the target object through the IR detector in the temperature measurement probe and converts it into a weak electrical signal. However, unlike the "direct signal processing within the probe" of integrated devices, the separated main unit can be far away from harsh environments such as high temperatures, dust, and vibration. It precisely amplifies, filters, linearly corrects, and performs data operations on electrical signals, and finally outputs the temperature value through the display screen. It simultaneously supports analog (4-20mA), digital (RS485/Modbus) and other signal outputs, facilitating integration into industrial control systems (such as DCS, PLC) for automated monitoring.

The core operation of an infrared pyrometer follows the fundamental law of thermal radiation: any object with a temperature above absolute zero (-273.15℃) will continuously radiate infrared rays (an invisible light) outward, and the intensity and wavelength distribution of the radiation are directly related to the temperature of the object.

According to Planck's law of radiation, the spectral distribution of an object's infrared radiation varies with temperature. The higher the temperature, the shorter the peak wavelength of the radiation and the stronger the total energy of the radiation. According to the Stefan-Boltzmann law, the total infrared radiation power per unit area of an object is directly proportional to the fourth power of the thermodynamic temperature, which is the key basis for the conversion between temperature and radiation energy. The infrared pyrometer captures the infrared radiation of the object being measured through an optical system. The infrared detector converts the radiation signal into an electrical signal, which is then amplified, filtered and compensated by the signal processing circuit. Finally, it is converted into the surface temperature of the object according to the preset algorithm and the reading is output through the display unit. Some models can also synchronously transmit the temperature signal to the control system.

In terms of performance characteristics, the separable infrared pyrometer usually has higher anti-interference ability and customization space: for electromagnetic interference in industrial sites, the main unit can integrate an electromagnetic shielding module; For different temperature measurement ranges (such as -50 ℃ to 1200℃), probes with different spectral responses can be matched. Some high-end models also support probe calibration function. Accuracy calibration can be completed through the main unit without disassembly, reducing maintenance costs.

The emissivity of an object (a parameter characterizing the object's ability to radiate infrared rays, with a value ranging from 0 to 1) directly affects the measurement accuracy. Therefore, most infrared pyrometers have an adjustable emissivity function and can be calibrated according to the characteristics of the material being measured (such as metals and non-metals) to ensure accurate results.

The reference table for the emissivity of common substances is as follows:

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