Infrared thermometer

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Infrared thermometers offer the ability to detect temperature optically -- through looking at an object, measuring its infrared energy radiation, and reinterpreting the radiation as temperature. They offer a method for accurately and quickly measuring temperature of an object at a distance and without needing to touch it -- ideal in situations where the object is moving rapidly, far away, extremely hot, within a dangerous environment, and/or the need to avoid contaminating the target object is critical (such as with food / medical equipment / pharmaceutical / electronics production or testing, etc.). Numerous infrared temperature sensing products are available on the market, ranging from flexible-use / portable or dedicated-function / affixed thermometers (such as that shown above), to more complex scanning and thermal imaging camera systems. This is an image of a specialized industrial infrared thermometer being used to monitor temperature of molten material for quality control purposes within a manufacturing process.

Infrared thermometers measure temperature using blackbody radiation (generally infrared) emitted from objects. They are sometimes called laser thermometers if a laser is used to help aim the thermometer, or non-contact thermometers to describe the device’s ability to measure temperature from a distance. By knowing the amount of infrared energy emitted by the object and its emissivity, the objects temperature can be determined.

The most basic design consists of a lens to focus the infrared energy on to a detector, which converts the energy to an electrical signal that can be displayed in units of temperature after being compensated for ambient temperature variation. This configuration facilitates temperature measurement from a distance without contact with the object to be measured. As such, the infrared thermometer is useful for measuring temperature under circumstances where thermocouples or other probe type sensors cannot be used or do not produce accurate data for a variety of reasons.

Some typical circumstances are where the object to be measured is moving; where the object is surrounded by an electromagnetic field, as in induction heating; where the object is contained in a vacuum or other controlled atmosphere; or in applications where a fast response is required.

Infrared thermometers can be used to serve a wide variety of temperature monitoring fuctions. A few examples provided to this article include:

Detecting clouds for remote telescope operation
Checking mechanical equipment or electrical circuit breaker boxes or outlets for hot spots
Checking heater or oven temperature, for calibration and control purposes
Detecting hot spots / performing diagnostics in electrical circuit board manufacturing
Checking for hot spots in fire fighting situations
Monitoring materials in process of heating and cooling, for research and development or manufacturing quality control situations

There are many varieties of infrared temperature sensing devices available today, including configurations designed for flexible and portable handheld use, as well many designed for mounting in a fixed position to serve a dedicated purpose for long periods.

Specifications of portable handheld sensors available to the home user will include ratings of temperature accuracy (usually plus or minus a degree or two), plus some other not so obvious measurements. The distance to spot ratio (D:S) measures the diameter of the temperature measurement area as it relates to the distance between the device and the surface being read. For instance, if your target area was one inch wide and you could get no closer than 12 inches to your target, you would need a sensor with a D:S of 12:1 or greater. Another feature is whether the sensor has a fixed or adjustable emissivity setting. If fixed, you would not get accurate readings from shiny surfaces (because most sensors are calibrated for non-shiny surfaces). Fixed emissivity sensors can be effective on shiny objects by just using tape or paint on your surface to compensate.

Typical sensor varieties include:

Spot Infrared Thermometers, also know as Infrared Pyrometers, designed for monitoring a finite area or "spot" of space

This image shows the results of a Line Scanning system measuring the shell temperature of a Cement Kiln.

Infrared Line Scanning Systems, typically incorporating what is essentially a spot thermometer pointed at a rotating mirror, for continuously scanning a wide area of space. These devices are widely used in manufacturing involving conveyors or "web" processes, such as large sheets of glass or metal exiting an oven, fabric and paper, or continuous piles of material along a conveyor belt.

Infrared Cameras, are essentially infrared thermometers designed as a camera, monitoring a thousand points at once, output as a two dimensional image, and with each pixel representing a temperature. This techonolgy is typically more processor and software intense than the items above, and is used for monitoring large areas of space. Typical applications include perimeter monitoring used by military or security personnel, inspection / process quality montioring of manufacturing processes, and equipment or enclosed space hot or cold spot monitoring for safety and efficiency maintenance purposes.

Infrared thermometer

See also