page_title: Air core gauge
section_title: Construction and operation
hierarchical_section_title: Air core gauge / Construction and operation
caption_attribution_description: English: Taken by WWriter and released to public domain on January 2, 2011. Picture is detail of back side of 2001 Honda Civic instrument cluster PC board. Arrows show four mounting terminals of a typical air core gauge.
context_page_description: An air core gauge is a specific type of rotary actuator in an analog display gauge that allows an indicator to rotate a full 360 degrees. It is used in gauges and displays, most commonly automotive instrument clusters.
  A typical automotive application is shown at the right. The air core gauge is a type of "air-core motor". It may be considered a "gauge movement" or "pointer indication device".
context_section_description: The air core gauge consists of two independent, perpendicular coils surrounding a hollow chamber.  A needle shaft protrudes into the chamber, where a permanent magnet is affixed to the shaft. When current flows through the perpendicular coils, their magnetic fields superimpose and the  magnet is free to align with the combined fields. 
   
  A typical air core gauge has four terminals, two for each coil, as shown. The two coils are identified as the sine coil and the cosine coil.
caption: Back side of an auto instrument cluster showing four mounting terminals for an air core gauge.
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