An infrared thermometer is a thermometer that summarizes the temperature of some thermal radiation that is sometimes called the black body radiation emitted by the measured object. They are sometimes called laser thermometers as lasers used to help direct the thermometer, or non-contact thermometer or temperature rifle , to illustrate the device's ability to measure temperature from long distance. By knowing the amount of infrared energy emitted by the object and its emissivity, the temperature of an object can often be determined within a certain actual temperature range. The infrared thermometer is part of a device known as a "thermal radiation thermometer".
Sometimes, especially near ambient temperatures, readings can be a mistake because of the reflection of radiation from the hotter body - even the person holding the instrument - rather than radiated by the measured object, and to the wrong emissivity.
The basic design consists of a lens for focusing infrared heat radiation to a detector, which converts the radiation power into electrical signals that can be displayed in unit temperature after being compensated for ambient temperature. This allows remote measurement of temperature without contact with the object to be measured. Non-contact infrared thermometers are useful for measuring temperatures in situations where thermocouples or other probe type sensors can not be used or do not produce accurate data for various reasons.
Video Infrared thermometer
Usage examples
Some typical circumstances are where the object to be measured moves; in which objects are surrounded by electromagnetic fields, as in induction heating; in which the object is contained in a vacuum or other controlled atmosphere; or in applications where quick response is required, the desired accurate surface temperature or object temperature above the recommended point of use for the contact sensor, or contact with the sensor will damage the object or sensor, or introduce a significant temperature gradient on the surface of the object.
Infrared thermometer can be used to serve various temperature monitoring functions. Some examples provided include detecting clouds for remote telescope operations, checking mechanical or electrical equipment for temperature and hotspots, measuring patient temperature in hospital without touching it, checking heating or oven temperature, for calibration and control, checking hotspots in fire fighting, monitoring materials in a process that involves heating or cooling, and measuring the temperature of the volcano. At the time of the epidemic of diseases that cause fever, such as coronavirus SARS and Ebola virus disease, infrared thermometers have been used to check travelers arrivals for fevers.
There are many types of infrared temperature sensing devices, both for portable and handheld usage and as fixed installations.
Maps Infrared thermometer
Accuracy
The infrared thermometer is characterized by specifications including accuracy and angular coverage. A simpler instrument may have measurement errors of about Ã, Â ± 2 Ã, Â ° C or Ã, Â ± 4Ã, Â ° F.
The distance-to-point ratio (D: S) is the ratio of the distance to the measuring surface and the diameter of the temperature measurement area. For example, if the ratio D: S is 12: 1, the diameter of the measuring area is one-twelve distances to the object. Thermometers with higher D ratios can sense a more specific and narrower surface at greater distances than those with lower ratios. 12: 1 rated devices can feel 1-inch circles at a distance of one foot, while a 10: 1 ratio device achieves the same 1-inch circle at 10 inches, and a wider and less specific circle 1.2 inches at 12 inches. The ideal target area should be at least twice the size of the place at that distance, with a smaller area relative to the distance resulting in a less accurate measurement. The infrared thermometer can not be placed too close to its target, or this proximity causes heat to accumulate in the thermometer housing and damage the sensor. The measurement error generally only decreases with too much distance due to the reflectivity effect and the inclusion of other heat sources in the sensor field of view.
According to Stefan-Boltzmann's law, the radiant power is proportional to the strength of the four temperatures, so that when the measuring surface has a hot and cold area, the indicated temperature may be higher than the actual average temperature, and closer to the mean fourth power mean.
Most surfaces have high emissivity (greater than 0.9 for most biological surfaces), and most IR thermometers rely on this simplification assumption; However, the reflective surface has a lower emissivity than a non-reflective surface. Some sensors have adjustable emissivity settings, which can be adjusted to measure reflective and non-reflective surface temperatures. An unadjustable thermometer can be used to measure reflective surface temperature by applying non-reflective paint or tape, with some loss of accuracy.
Sensors with adjustable emissivity settings can also be used to calibrate the sensor for a particular surface, or to measure surface emissivity. When the surface temperature is known accurately (eg by measuring with the contact thermometer), the sensor emissivity setting can be adjusted until the temperature measurement by the IR method corresponds to the temperature measured by the contact method; the emissivity arrangement will show surface emissivity, which can be accounted for for subsequent measurements of the same surface (only).
Infrared pirameter
The most common infrared pirameter is the infrared pyramid of the place or the infrared pyrometer, which measures the temperature at a point on the surface (actually a relatively small area determined by the ratio D: S). It usually projects a visible red dot to the center of the measured area that identifies the point measured, but does not play a part in the measurement. The actual measured angular area varies between instruments and is not limited to visible places.
The related equipment, though not completely thermometer, includes an infrared scanning system and a thermal infrared imaging camera. The infrared scanning system scans a larger area, typically using what is essentially a spot thermometer directed to a rotating mirror. This device is widely used in manufacturing that involves conveyors or "web" processes, such as large sheets of glass or metal coming out of the oven, fabric and paper, or piles of material continuously along the conveyor belt. An infrared thermal imaging camera or infrared camera is essentially an infrared radiation thermometer that measures the temperature at many points over a relatively large area to produce a two-dimensional image, called a thermogram, with each pixel representing temperature. This technology is more processor- and software-intensive than spot or scanning thermometers, and is used to monitor large areas. Typical applications include perimeter monitoring used by military or security personnel, process quality monitoring/manufacturing process inspections, and hot spot or chamber monitoring equipment or spaces for safety and efficiency purposes.
Photography camera using infrared film and corresponding lens, etc., Also called "infrared camera". It only captures near infrared and is insensitive to thermal radiation from room temperature objects.
Gallery
See also
- ASTM E20.02 Subcommittee on Thermometric Radiation
- Bolometer
- Pyrometer
- the Sakuma-Hattori equation
- Thermographic camera
- Thermography
References
External links
- Avoiding Common Mistakes That Can Compromise Infrared Inspection Programs
- Introduction to Infrared Thermometer - Omega
Source of the article : Wikipedia
0 Comments