Pirometers
(71)Pyrometers are devices that allow for non-contact temperature measurement. Due to their wide measurement range and speed, they are used in a variety of applications: heating and cooling systems, HVAC, transportation (especially vehicle servicing, not limited to cars), food industry, pharmaceuticals, and even energy production. Importantly, this method of measurement allows for examining rotating elements (detecting friction points), connections under voltage (sections of increased resistance), or objects in hazardous areas. Considering this vast range of applications, let’s explore the functionality of pyrometers and their basic features.
Principle of Operation
Pyrometers use the phenomenon of thermal radiation to measure temperature. All bodies with a temperature above absolute zero emit electromagnetic waves. Their wavelength falls within the infrared (IR) light range. By measuring the intensity of this radiation, one can estimate the temperature of an object with high accuracy. In pyrometers, an optoelectronic, light-sensitive element is used for this purpose. To ensure the measurement is performed in a specific area, IR rays are focused on the light-sensitive surface using a simple lens. The A/C converter and a specially programmed circuit process the data.
Types of Pyrometers
The main and most obvious division of pyrometers is based on their purpose and construction. Although the operating principle is the same for all devices, they differ in precision and functionality (which are described below).
Portable Pyrometers
The most common type is handheld pyrometers, where the measurement element is placed on a handle. In most models, the handle contains a battery compartment, and a trigger at the top is used to activate the measurement. This design allows the device to be operated with one hand and easily aimed at the target object. The handle houses the pyrometer module with the lens, and on the operator’s side, there is a display (usually LCD) showing the results and settings, as well as buttons to change them. The design and usage of portable devices are relatively uniform, regardless of their specific purpose. Specific features of these devices are discussed below.
Pyrometers for Industrial Automation
For pyrometers used in automation systems, the meter module is much more compact – allowing it to be mounted in various orientations and confined spaces. Power and measurement data are transmitted using standard industrial connectors, so this module is not a standalone unit. In most cases, they are installed statically. Since they can measure from a distance and operate within a relatively wide temperature range, they are used in industrial settings for non-contact temperature measurements of furnaces, elements at extreme temperatures, and in systems requiring high hygiene (food, chemical, pharmaceutical industries, etc.). As the light-sensitive element is connected to an external controller, measurements can be taken faster (with a higher frequency) compared to handheld devices.
Additional Features of Pyrometers
The functionality of pyrometers intended for automation systems depends on the model: they can be highly configurable or act as a type of thermal sensor. For handheld models, manufacturers equip them with various features to facilitate measurement collection, especially for routine and periodic tasks. When selecting a pyrometer, it is worth considering how these extended features impact work ergonomics.
Optical Resolution and Laser Pointer
Standard equipment for handheld pyrometers includes a laser pointer, indicating the measured surface. It is important to note that this is not a single point. Due to the operating principle, a pyrometer measures the intensity of radiation emitted over a specific area.
The optical characteristics are provided in the manual to inform the user from what distance to conduct the measurement. The most crucial part of this specification is the optical resolution, indicating the area from which the electromagnetic waves are collected for measurement. Infrared radiation is focused on the light-sensitive element using a lens – the pyrometer's field of view can thus be described as a cone, with the vertex located on the measuring component and perpendicular to its surface. The farther from the lens, the wider the area from which infrared radiation is collected (decreasing precision over longer distances). In most pyrometers, the laser beam indicates the cone's height, but some models emit additional beams to outline the cone's base, showing the operator the measured area. This is especially useful when collecting data in complex heating, cooling, or HVAC installations where pipes and ducts are closely spaced.
Regarding factors influencing measurement results, it is essential to note that nearly all bodies reflect infrared radiation from other sources (similar to how they reflect visible light), meaning the ambient temperature slightly affects the readings.
Acoustic and Visual Alarms
In some situations, the exact temperature may not be important to the pyrometer user – as long as it does not exceed threshold values. This is the case during routine inspections to check for overheating or undercooling of specific areas or system components. Therefore, some pyrometer models allow setting threshold values and emit an acoustic and/or visual alarm when the measured temperature falls outside the set range. This simple feature significantly speeds up various maintenance and service tasks.
MIN, MAX, AVG Functions
When taking measurements on objects with fluctuating temperatures (e.g., thermoregulatory components, HVAC system points), it is helpful to have the device remember the extreme values recorded over a specific period. The MIN and MAX functions indicate the lowest and highest temperatures measured while pressing the activation trigger. Additionally, many devices have an AVG (average) function, useful for measuring large areas like hydraulic/pneumatic systems or photovoltaic panels, to estimate overall losses and optimize performance.
Measurement Memory and Communication
If the pyrometer will be used frequently and regularly, such as for inspecting extensive installations, investing in a device with advanced features like built-in memory and the ability to export results to a computer (for further processing or reporting) might be beneficial. Such models communicate via wireless protocols (Bluetooth, WiFi), common connectors (USB), or sometimes support removable memory cards. The collected data can easily be exported as a file for analysis or reporting.
Key Parameters of Pyrometers
When choosing a pyrometer, in addition to the features described above, it is crucial to consider several key parameters. The first is, of course, the measurement range, defining the thermal range the meter operates within. Measurement resolution will also be significant. Furthermore, most devices allow adjustable emissivity correction (determined by factors such as material, state, texture, and viewing angle of the object).
Personal preferences come into play when considering the size and weight of the device, as well as the screen size. Accessories like probes, thermocouples, cases, or carrying bags included with the pyrometer should also be considered. If the device will be used frequently, investing in a model powered by a rechargeable battery could be worthwhile. For professional applications, the sensor calibration certificate becomes important. Additionally, pay attention to the protection class (waterproofing), which is often very high (e.g., IP65), allowing use in harsh environments.
For pyrometers mounted in industrial automation or serving a control function in other systems, aside from the parameters mentioned, the key feature is the device's interface. Many such products can communicate using standard industrial protocols like Profibus or RS485.
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