What is the difference between halogen and infrared hygrometers?
The thermogravimetric moisture analyzer effectively dries the sample by transferring energy in the form of waves or particles through radiation (through waves) and convection (through mass motion for heat transfer) through the medium (in this case, the sample). In contrast, traditional drying furnaces mainly use convection to dry samples. Both metal and halogen heating elements emit energy in the infrared spectrum.
Infrared (IR) radiation is a part of the electromagnetic spectrum, located between microwave energy and visible light. Infrared radiation includes thermal radiation, with a wavelength frequency range of 0.75 microns (the long wavelength limit of visible red light) to 1.5 microns (the boundary on microwaves). The human eye cannot see infrared energy. The red light usually associated with infrared heating is actually reflected red light from the visible spectrum.
Some moisture analyzers use metal heating elements, which are only low resistance metal sheets that convert electricity into heat. This type of heater is very suitable for environments where the use of glass components is prohibited due to regulatory or safety considerations, such as food processing. Metal heaters are not satisfactory because they have a very large amount of heat and require much longer heating time than halogen heaters, making them difficult to control and unable to provide good repeatability in moisture meters.
The halogen radiator is equipped with a tungsten heating element in a compact glass tube, which contains halogen gas to preserve the tungsten element. Halogen radiators emit infrared radiation in the short wavelength range of 0.75 to 1.5 microns. The compact characteristics of halogen radiators improve heating/cooling response time, shorten the time for the heating unit to reach full heating power, and ultimately shorten the time to complete sample drying. It can also provide better control during the heating process.
