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micrometermore about micrometer

micrometer

 

  2  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Micrometer  \Mi*crom"e*ter\,  n.  [Micro-  +  -meter:  cf  F. 
  microm[`e]tre.] 
  An  instrument,  used  with  a  telescope  or  microscope,  for 
  measuring  minute  distances,  or  the  apparent  diameters  of 
  objects  which  subtend  minute  angles.  The  measurement  given 
  directly  is  that  of  the  image  of  the  object  formed  at  the 
  focus  of  the  object  glass. 
 
  {Circular,  or  Ring},  {micrometer},  a  metallic  ring  fixed  in 
  the  focus  of  the  object  glass  of  a  telescope,  and  used  to 
  determine  differences  of  right  ascension  and  declination 
  between  stars  by  observations  of  the  times  at  which  the 
  stars  cross  the  inner  or  outer  periphery  of  the  ring. 
 
  {Double  image  micrometer},  a  micrometer  in  which  two  images 
  of  an  object  are  formed  in  the  field,  usually  by  the  two 
  halves  of  a  bisected  lens  which  are  movable  along  their 
  line  of  section  by  a  screw,  and  distances  are  determined 
  by  the  number  of  screw  revolutions  necessary  to  bring  the 
  points  to  be  measured  into  optical  coincidence.  When  the 
  two  images  are  formed  by  a  bisected  object  glass,  it  is 
  called  a  divided-object-glass  micrometer,  and  when  the 
  instrument  is  large  and  equatorially  mounted,  it  is  known 
  as  a  heliometer. 
 
  {Double  refraction  micrometer},  a  species  of  double  image 
  micrometer,  in  which  the  two  images  are  formed  by  the 
  double  refraction  of  rock  crystal. 
 
  {Filar,  or  Bifilar},  {micrometer}.  See  under  {Bifilar}. 
 
  {Micrometer}  {caliper  or  gauge}  (Mech.),  a  caliper  or  gauge 
  with  a  micrometer  screw,  for  measuring  dimensions  with 
  great  accuracy. 
 
  {Micrometer  head},  the  head  of  a  micrometer  screw. 
 
  {Micrometer  microscope},  a  compound  microscope  combined  with 
  a  filar  micrometer,  used  chiefly  for  reading  and 
  subdividing  the  divisions  of  large  astronomical  and 
  geodetical  instruments. 
 
  {Micrometer  screw},  a  screw  with  a  graduated  head  used  in 
  some  forms  of  micrometers. 
 
  {Position  micrometer}.  See  under  {Position}. 
 
  {Scale},  or  {Linear},  {micrometer},  a  minute  and  very 
  delicately  graduated  scale  of  equal  parts  used  in  the 
  field  of  a  telescope  or  microscope,  for  measuring 
  distances  by  direct  comparison. 
 
  From  WordNet  r  1.6  [wn]: 
 
  micrometer 
  n  1:  a  metric  unit  of  length  equal  to  one  millionth  of  a  meter 
  [syn:  {micron},  {micrometre}] 
  2:  for  measuring  small  distances  [syn:  {micrometer  gauge},  {micrometer 
  caliper}]




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