What is the difference between halogen and infrared moisture analyzers?
Thermogravimetric moisture analyzers effectively dry samples by transferring energy through radiation (energy in the form of waves or particles through a medium (in this case, the sample)) and convection (heat transfer through mass movement). Compare Below, traditional drying ovens primarily use convection to dry samples. Both metal and halogen heating elements radiate energy in the infrared spectrum. (Both methods are used in the OHAUS MB Series.)
Infrared (IR) radiation is a part of the electromagnetic spectrum, between microwave energy and visible light. Infrared includes thermal radiation with wavelength frequencies ranging from 0.75 microns (the long wavelength limit of visible red light) to 1.5 microns (the boundary on microwaves). Infrared energy is invisible to the human eye. The red light often associated with infrared heating is actually reflected red light from the visible spectrum.
Some moisture analyzers use metal heating elements, which are simply low-resistance metal pieces that convert electricity into heat. This heater is ideal for environments where the use of glass components is prohibited due to regulatory or safety concerns (e.g. food processing). Metal heaters are not desirable because they generate a lot of heat, take much longer to heat than halogen heaters, are difficult to control and do not provide good reproducibility in moisture analyzers.
Halogen radiators contain a tungsten heating element in a compact glass tube that contains halogen gas to preserve the tungsten element. Halogen radiators emit infrared radiation in the short wavelength range of 0.75-1.5 microns. The compact nature of the halogen radiator improves heating/cooling response times, shortening the time it takes the heating unit to reach full heating power and ultimately shortening the time it takes to complete sample drying. It also allows for better control during the heating process.
