hi temp snap disc thermostats

Discussion in 'General Electronics Chat' started by aac9876, Jan 26, 2009.

  1. aac9876

    Thread Starter Active Member

    Dec 9, 2006
    124
    0
    how Exactly do these work..??? how do they move or make contact ..????
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I think these work on the principle of a bi-metal strip. By bonding two thin pieces of metal together each with a different coefficient of thermal expansion, one of the two strips will expand to a greater length than the other and so the metal strip will deform and make or break a contact between the two terminals.

    hgmjr
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    ...and in the form of a slightly cupped disk, the difference in expansions makes a quick snap. This type of switch is often used as a thermal overload protection in motors.
     
  4. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287

    Yeah...most of the ones I've worked with had to be manually reset. My old HP 524 frequency counter had one of those, in case it overheated from all 347 vacuum tubes....yeah, like THAT was ever going to happen! :rolleyes:

    Eric
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Manual reset offers the opportunity to fix the root problem without undue torture to the system. Automatic reset allows the system to keep cycling into an overheat condition. I suspect the filaments in vacuum tubes last longer when they are cycled less. Locked rotor motors certainly do! :cool:
     
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