It is a type of heating element that is encased in a protective sheath, which is commonly used in various appliances for efficient and safe heating.

You can go through these links which explains such concept:MKS Instruments - This site often discusses various types of heating solutions including those that may use sheath heaters in electronics and industrial applications.
https://www.mks.com/

Energy Assistance Programs - NYC.gov - While this resource is more focused on heating assistance programs, it sometimes touches upon various heating technologies, which may include sheath heaters.
https://www.nyc.gov/site/hra/help/energy-assistance.page

Omega Engineering - Provides detailed information about different heating solutions, including cartridge heaters, which are similar to sheath heaters. This can be particularly insightful for understanding the use of sheath heaters in electronic applications.
https://www.omega.com/en-us/resources/cartridge-heaters

Tansun - Discusses quartz heating, which often uses sheathed elements for infrared heating solutions. This could provide a practical understanding of how sheath heaters are implemented in certain products.
https://www.tansun.com/gb_en/technical/how-quartz-heating-wo...

Cuptor incorporabil cu triplă distribuție, 23L - FG87SUB/BOL at Samsung Romania:
This page on the Samsung Romania website lists microwave ovens with specifications that likely include sheath heaters, described as încălzitor cu teacă. It might provide practical examples of such devices in household appliances. You can access detailed information and product specifications here: https://www.samsung.com/ro/microwave-ovens/grill/microwave-o...