What is the difference between a halogen Moisture Meter and an infrared Moisture Meter?

Thermogravimetric moisture analyzers dry samples efficiently by transferring energy radiatively (via waves) through the medium (in this case the sample) and convectively (heat transfer by mass motion) as energy in the form of waves or particles. In contrast, conventional Drying Ovens primarily use convection to dry samples. Both metal and halogen heating elements radiate energy in the infrared spectrum.

Infrared (IR) radiation is the part of the electromagnetic spectrum that lies between microwave energy and visible light. Infrared includes thermal radiation with wavelengths in the frequency range of 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.

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Some moisture analyzers use metal heating elements, which are simply low resistance pieces of metal that convert electricity into heat. These heaters are ideal for environments where the use of glass components is prohibited due to regulatory or safety concerns, such as food processing. Metal heaters are not desirable because they are very hot and take much longer to heat up than halogen heaters, are difficult to control and do not provide good repeatability in a moisture analyzer.

Halogen radiators contain a tungsten heating element in a compact glass tube that contains a 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 irradiators improves heating/cooling response times, reduces the time for the heating unit to reach full heating power and ultimately reduces the time to complete sample drying. It also allows for better control during heating.