Intro
Other applications
Specifications
Instructions
FAQ
Ordering
|
Intro |
What is Infrared Radiation (IR)?
IR, just like any light ray is an Electromagnetic Radiation, with lower frequency (or longer wavelength). The primary source of infrared radiation is heat or thermal radiation. This is the radiation produced by the motion of atoms and molecules in an object. The higher the temperature, the more the atoms and molecules move and the more infrared radiation they produce. Any object that has a temperature i.e. anything above absolute zero (-459.67 degrees Fahrenheit or -273.15 degrees Celsius or 0 degrees Kelvin), radiates in the infrared. Absolute zero is the temperature at which all atomic and molecular motion ceases. Even objects that we think of as being very cold, such as an ice cube, emit infrared. When an object is not quite hot enough to radiate visible light, it will emit most of its energy in the infrared.
This is because your eyes are designed for Sunlight. However, there are species of animals that have been identified, which are able to detect IR: including some types of rattlesnake & beetles. However, even though you can't see it, you can still sense IR by your skin. For example, hot charcoal may not give off light but it does emit infrared radiation, which we feel as heat. The warmer the object, the more infrared radiation it emits: e.g. beside a campfire, you can feel the warmth from the IR.
What kind of theory/technology is involved in IR?
Believe or not, Quantum physics is the key theory: the total radiation energy is proportional to the fourth power of the absolute temperature (Stefan-Boltzmann Law). Wien Displacement Law: the product of the peak wavelength and the temperature is found to be a constant - Wien got the Nobel Prize for Physics for the year 1911.
These are the major landmarks in physics: after that Classic Physics crashed and Quantum Physics flourished.
The sensor in this device collects the tiny amount of energy from the target, (usually 0.0001 watt), it is then amplified by a precision amp, converting it into voltage output. The CPU then digitises the signal using a digital converter, into arithmetic units. It is at this point that it can be shown as a temperature using the equations of the above Nobel Prize Laws. By compensating for the ambient temperature and emissivity effect, you get the temperature of the target within seconds of pushing the button.
All objects reflect, transmit and emit energy. Emissivity is the measure of an object's ability to emit infrared energy - the emitted energy indicates the temperature of the object. When the MH-1 measures the surface temperature it senses this energy. Emissivity can have a value from 0 (shiny mirror surface) to 1.0 (blackbody). Most organic, painted, or oxidized surfaces have emissivity values close to 0.95 (the MH-1 is set at 0.95).
When using a thermometer with a fixed, preset emissivity of 0.95 and need to accurately measure a shiny object, you can compensate by covering the surface to be measured with masking tape, (spray oil or flat black paint could be used on machine parts) then measure the temperature of the taped or painted surface. That is the true temperature. Dealing with emissivity is not as hard as it would seem. The important thing to remember is that "trending" an object can reveal problems regardless of accurate temperature. In the real world you pick an emissivity value and then record the temperature, making sure to maintain the same setting every time you scan the same object. We hope this answers the basic questions regarding emissivity as a full explanation of emissivity is beyond the scope of this web site.
Note: the temperatures of some highly polished metal surfaces are difficult to measure.
|
Intro |