The principle and application of infrared thermometer
The infrared thermometer converts the radiant energy of the infrared ray emitted by the object into an electrical signal. The size of the infrared radiant energy corresponds to the temperature of the object itself. According to the size of the converted electrical signal, the temperature of the object can be determined.
1. The principle of infrared thermometer
The infrared thermometer is composed of optical system, photoelectric detector, signal amplifier, signal processing, display output and other parts. The optical system gathers the target infrared radiation energy in its field of view, and the size of the field of view is determined by the optical parts of the thermometer and its position. Infrared energy is focused on a photodetector and converted into a corresponding electrical signal. The signal passes through the amplifier and signal processing circuit, and is converted into the temperature value of the measured target after being corrected according to the algorithm of the internal treatment of the instrument and the emissivity of the target.
In nature, all objects with a temperature higher than zero are constantly emitting infrared radiation energy to the surrounding space. The magnitude of the infrared radiation energy of an object and its distribution according to the wavelength - has a very close relationship with its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined, which is the objective basis for infrared radiation temperature measurement.
Principle of Infrared Thermometer Blackbody is an idealized radiator, which absorbs all wavelengths of radiation energy, has no reflection and transmission of energy, and has an emissivity of 1 on its surface. However, practical objects in nature are almost not black bodies. In order to clarify and obtain the distribution of infrared radiation, an appropriate model must be selected in theoretical research. This is the quantized oscillator model of body cavity radiation proposed by Planck, thus Derived the law of Planck's black body radiation, that is, the black body spectral radiance expressed by wavelength, which is the starting point of all infrared radiation theories, so it is called the law of black body radiation. The radiation amount of all actual objects depends not only on the radiation wavelength and the temperature of the object, but also on the type of material constituting the object, the preparation method, the thermal process, the surface state and the environmental conditions. Therefore, in order to make the law of black body radiation applicable to all practical objects, a proportional coefficient related to material properties and surface states must be introduced, that is, emissivity. This coefficient represents how close the thermal radiation of an actual object is to the radiation of a black body, and its value is between zero and a value less than 1. According to the law of radiation, as long as the emissivity of the material is known, the infrared radiation characteristics of any object are known. The main factors affecting emissivity are: material type, surface roughness, physical and chemical structure, and material thickness.
When using an infrared radiation thermometer to measure the temperature of a target, it is first necessary to measure the infrared radiation of the target within its band range, and then the temperature of the measured target is calculated by the thermometer. A monochromatic pyrometer is proportional to the amount of radiation within a band; a two-color pyrometer is proportional to the ratio of the amount of radiation in the two bands.
Second, the application of infrared thermometer
Infrared thermometer is a commonly used temperature measuring instrument, mainly composed of optical system, photodetector, signal amplifier, signal processing, display output and other parts, and is widely used in many industries. Today we mainly introduce the application range of infrared thermometers, hoping to help users better apply the products.
Measuring electrical equipment
Non-contact infrared thermometers can measure the surface temperature of an object from a safe distance, making them an indispensable tool in electrical equipment maintenance operations.
Applications in electrical equipment
In the following applications, it can effectively prevent equipment failures and unplanned power outages.
Connectors—Electrical connections can gradually loosen connectors due to repeated heating (expansion) and cooling (shrinkage) to generate heat, or surface dirt, carbon deposits, and corrosion. Non-contact thermometers can quickly identify temperature rises that indicate a serious problem.
Motor - To preserve the life of the motor, check that the power connection wires and the circuit breaker (or fuse) are at the same temperature.
Motor Bearings - Check for hot spots and repair or replace them regularly before problems cause equipment failure.
Motor Coil Insulation - Extend the life of your motor coil insulation by measuring its temperature.
Measurements Between Phases - Checks that wires and connectors in induction motors, mainframe computers and other equipment are at the same temperature between phases.
Transformer - Windings of air-cooled devices can be measured directly with an infrared thermometer to check for excessive temperatures, any hot spots indicate damage to the transformer windings.
Uninterruptible Power Supply - Identify hot spots on the connecting wires on the UPS output filter. A cool spot may indicate an open circuit in the DC filter line.
Backup Battery - Check the low voltage battery to make sure it is connected properly. Poor contact with the battery terminals can heat up enough to burn the battery core rods.
Ballast - Check for overheating of the ballast before it starts smoking.
Utilities - Identify hot spots for connectors, wire splices, transformers and other equipment. Certain models of optical instruments have a range of 60:1 or even greater, bringing almost all measurement targets within range.
