Forberg Scientific offers a complete line of Wika Temperature Instruments including Bimetal Thermometers which are available for purchase at www.forberg.com . Styles ranging from pocket test thermometers to process grade thermometers and industrial-grade thermometers are available. These temperature instruments have cases and bezels that are made from sturdy, corrosion resistant 304 stainless steel and incorporate anti-parallax heavy gauge aluminum dials that incorporate a white matte finish to reduce glare. Stem lengths to 72 inches are available as well as 316SS stem and connector assemblies. Wika bimetal thermometers are guaranteed to be accurate to within one percent of full scale (Grade A per ASME B40.3). Calibration is to standards traceable to the National Institute of Standards and Technology. Wika extends a seven year warranty on standard bimetal thermometer types 30, 31, 50, 51, 32, & 52.
Bimetal Thermometer: Theory of Operation
The temperature is measured with a bimetal system inside the thermometer stem. The bimetal system consists of two metal strips bonded together that have different expansion coefficients. Therefore, one strip will expand faster than the other causing the bimetal strip to curl in proportion to its temperature. The bimetal system is helically wound and heat treated for long term stability. Temperature variations cause the bimetal strip to unwind or wind tighter, which in turn rotates the pointer.