Billede:Moving coil instrument principle.png

Shows the working principle for a moving coil intrument. Legend for numbers in the illustration:

1. Core for moving coil
2. Permanent magnet
3. Pole "shoe" for focusing magnetic field
4. Dial
5. Aiming mirror on dial
6. Coil spring
7. Coil
8. Coil at rest
9. Coil at full deflection
10. Coil yoke
11. Adjustment screw for mechanical zero alignment
12. Pointer
13. Pointer at rest
14. Pointer at full deflection

Rendered using POV-Ray (see http://www.povray.org/). The scene description code below supports rendering both of the two sections in this illustration; the overall view at the top, and the close-up below. The two sections were subsequently combined, and the numbers added, in a graphics software package.

 /*
 =======================================================
 Demonstrating the principle of a moving coil instrument
 -------------------------------------------------------
 Created by Søren Peo Pedersen - see my user page at
 http://da.wikipedia.org/wiki/Bruger:Peo
 =======================================================
 */
 
 #declare CloseUp=yes;
 #declare Fontname="arialbd.ttf";
 
 
 global_settings {max_trace_level 256}
 
 #local txtMetal=texture {
   pigment {color rgb .5}
   finish {
       metallic
       phong 1
       reflection .5
       }
   }
 
 #include "functions.inc"
 #local CoilSpring=isosurface {function {f_spiral(-x,z/5,y,.2,.01,1.34,0,0,0)}
     contained_by { box {<-2,-2,-.2>,<2,2,.2>} }  // container shape
     accuracy 0.001                      // accuracy of calculation [0.001]
     max_gradient 4                      // maximum gradient the function can have [1.1]
     texture {txtMetal}
     }
 
 #macro txtCoilYoke(Transparency)
     texture {pigment {color rgbt <.5,1,0,Transparency>} finish {ambient .4}}
 #end
 
 #macro MovingPart(Transparency)
   #local txtCopper=texture {  // Texture for copper wire in coil
     pigment {color 
       #if (Transparency=0)
         rgb <.5,.25,.15>
       #else
         rgbt <1,.5,.3,Transparency>
       #end
       }
     finish {            
       #if (Transparency=0)
         metallic 1
         reflection rgb <1,.5,.3> 
         phong 1
         ambient .4
       #end
       }
     }
   
   #local FramePart=merge {  // One of four "sides" in the square-shaped coil
     difference {  // Staright parts of coil yoke
       box {<-.3,1,-1.00001>,<.3,1.5,1.00001>}
       box {<-.25,1.05,-2>,<.25,2,2>}
       txtCoilYoke(Transparency)
       }
     difference {  // Rounded corners of coil yoke
       cylinder {<-.3,1,-1>,<.3,1,-1>,.5}
       box {<-.25,0,-2>,<.25,2,0>}
       box {<-1,1,-2>,<1,2,-1> inverse}
       txtCoilYoke(Transparency)
       }
     
     #local n=0; // Outermost layer of windings on coil
     #while (n<11)
         cylinder {<-.275+.05*n,1.4,-1.00001>,<-.275+.05*n,1.4,1.00001>,.025 texture {txtCopper}}
         intersection {
             torus {.4,.025}
             box {<0,-1,-1>,<1,1,0>}
             rotate <0,0,90>
             translate <-.275+.05*n,1,-1>
             texture {txtCopper}
             }
         #local n=n+1;
     #end
     
     #local n=0;
     #while (n<7)
       cylinder {<.225,1.35-.05*n,-1.00001>,<.225,1.35-.05*n,1.00001>,.025 texture {txtCopper}}
       intersection {
         torus {.35-.05*n,.025}
         box {<0,-1,-1>,<1,1,0>}
         rotate <0,0,90>
         translate <.225,1,-1>
         texture {txtCopper}
         }
       #local n=n+1;
     #end
     
     }
   
   #merge {  // The entire mobile coil on its yoke:
       #object {FramePart}
       #object {FramePart rotate <90,0,0>}
       #object {FramePart rotate <180,0,0>}
       #object {FramePart rotate <270,0,0>}        
       box {<-.03,0,-1.79>,<.03,5,-1.81> // Needle
         pigment {color rgbt <0,0,0,Transparency>}
         rotate <0,0,-45>
         }
       }
 #end
 
 #declare MagnetPoleShoe=merge {
   cylinder {<-1.44222,-.9,-.8>,<-1.44222,-.9,.8>,.1}
   cylinder {<-1.44222, .9,-.8>,<-1.44222, .9,.8>,.1}
   sphere {<-1.44222,-.9,-.8>,.1}
   sphere {<-1.44222, .9,-.8>,.1}
   sphere {<-1.44222,-.9, .8>,.1}
   sphere {<-1.44222, .9, .8>,.1}
   cylinder {<-1.44222,-.9,-.8>,<-1.8,-.9,-.8>,.1}
   cylinder {<-1.44222,-.9, .8>,<-1.8,-.9, .8>,.1}
   cylinder {<-1.44222, .9,-.8>,<-1.8, .9,-.8>,.1}
   cylinder {<-1.44222, .9, .8>,<-1.8, .9, .8>,.1}
   box {<-1.8,.9,-.8>,<-1.44222,1,.8>}
   box {<-1.8,-1,-.8>,<-1.44222,-.9,.8>}
   difference {
     box {<-1.8,-.9,-.9>,<0,.9,.9>}
     cylinder {<0,0,-5>,<0,0,5>,1.7}
     }
   difference {
     box {<-1.799999,-.837596,-.8>,<0,.837596,.8>}
     cylinder {<0,0,-5>,<0,0,5>,1.6}
     }
   difference {
     merge {
       torus {1.7,.1 rotate <90,0,0> translate <0,0,-.8>}
       torus {1.7,.1 rotate <90,0,0> translate <0,0,.8>}
       }
     plane {<0,1,0>,0 rotate <0,0,31.9657>}
     plane {<0,-1,0>,0 rotate <0,0,-31.9657>}
     }
   texture {txtMetal}
   }
 
 #object {MagnetPoleShoe}
 #object {MagnetPoleShoe scale <-1,1,1>}
 
 #if (CloseUp)
   #object{MovingPart(0) translate <0,0,.000001>}
   #object {MovingPart(.7) rotate <0,0,90>}
 #else
   #object{MovingPart(0) rotate <0,0,21>}
 #end
 
 cylinder {<0,0,-2>,<0,0,-1.5>,.4 txtCoilYoke(0)}
 cylinder {<0,0,1.5>,<0,0,1.7>,.4 txtCoilYoke(0)}
 cylinder {<0,0,-2.5>,<0,0,-2>,.1 texture {txtMetal}}
 cylinder {<0,0,1.7>,<0,0,2.2>,.1 texture {txtMetal}}
 
 #object {CoilSpring translate <0,0,1.6>}
 #object {CoilSpring translate <0,0,-1.6>}
 
 merge { // Core inside moving coil
     cylinder {<0,0,-.9>,<0,0,.9>,.8}
     cylinder {<0,0,-.8>,<0,0,.8>,.9}
     torus {.8,.1 rotate <90,0,0> translate <0,0,-.8>}
     torus {.8,.1 rotate <90,0,0> translate <0,0,.8>}
     texture {txtMetal}
     }
 
 merge { // Frame & screw for mechanical adjustment
   difference {
     box {<-.2,-2,-2.8>,<.2,.2,2.5>}
     box {<-1,-1.25,-2.2>,<1,1,1.9>}
     box {<-1,-1.6,-1.5>,<1,1,1.5>}
     }
   cylinder {<0,0,-2.8>,<0,0,-3.3>,.2}
   difference {
     cylinder {<0,0,-3.3>,<0,0,-4>,.4}
     sphere {<0,0,-2>,1.6 inverse}
     box {<-1,-.1,-5>,<1,.1,-3.4>}
     }
   pigment {color rgb <0,.5,1>}
   finish {ambient .4}
   }
   
 difference {  // Horse-shoe permanent magnet
   merge {
     box {<-3.8,-1,-1>,<3.8,3,1>}
     cylinder {<0,3,-1.000001>,<0,3,1.000001>,3.8}
     }
   box {<-1.8,-2,-2>,<1.8,3,2>}
   cylinder {<0,3,-2>,<0,3,2>,1.8}
   pigment {
     object {
       union {
         text {ttf Fontname,"S",1,0 scale 3.1 translate <-3.7,-.85,-1.5>}
         difference {
           plane {<-1,0,0>,0}
           text {ttf Fontname,"N",1,0 scale 3.1 translate <1.9,-.85,-1.5>}
           }        
         }
       color rgb 1
       color rgb <1,0,0>
       }
     }
   finish {ambient .4}
   }   
 
 box {<-4.3,3,-1.7>,<4.3,6,-1.68>  // Scale behind needle:
   pigment {
     object {
       union {
         #local n=0;
         #while (n<101)
           #local h=5.1;
           #if (n/5=int(n/5)) #local h=5.2; #end
           #if (n/10=int(n/10))
             #local h=5.3;
             #local Number=text {ttf Fontname,str(n/10,0,0),.04,0 scale .5}
             #object {
               Number
               translate <(min_extent(Number).x-max_extent(Number).x)/2,5.35,-1.71>
               rotate <0,0,45-.9*n>
               }
           #end
           box {
             <-.01,4.8,-1.71>,<.01,h,-1.69>
             rotate <0,0,45-.9*n>
             }
           #local n=n+1;
         #end
         }
       color rgbt <1,1,1,.5>
       color rgbt <0,0,0,.5>
       }
     }
   finish {ambient .4}
   }
 
 difference {
   cylinder {<0,0,-1.7002>,<0,0,-1.7001>,4.75}
   cylinder {<0,0,-2>,<0,0,-1>,4.55}
   box {<0,0,-2>,<9,9,-1> inverse rotate <0,0,45>}
   pigment {color rgb 0}
   finish {reflection .95}
   }
 
 #declare Spotty=pigment {
   bozo
   color_map {
     [0 color rgb .5]
     [1 color rgb 1]
     }
   scale .05
   }
   
 sky_sphere {
   pigment {
     gradient z
     pigment_map {
       [0 Spotty]
       [.8 Spotty]
       [.913 color rgb <1,1,1>]
       [1 color rgb <1,1,1>]
       }
     scale 2
     translate <0,0,-1>
     rotate <15.5,28.5,0>
     }
   }
 
 camera {
   up <0,1,0> right <.93,0,0>
   location <-5,5,-9>
   #if (CloseUp)
     look_at <0,-.45,-.8> angle 24
   #else
     look_at <-.55,2.4,-.8>
   #end
   }
 
 light_source {<50,150,100> color rgb 1}
 light_source {<-100,80,-150> color rgb 1}

I, the author of this work, hereby publish it under the following license: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". العربية | Asturianu | Български | বাংলা | ইমার ঠার | Brezhoneg | Bosanski | Català | Sinugboanong Binisaya | Česky | Dansk | Deutsch | Ελληνικά | English | Esperanto | Español | Eesti | Euskara | فارسی | Suomi | Français | Galego | עברית | Hrvatski | Magyar | Bahasa Indonesia | Ido | Íslenska | Italiano | 日本語 | ქართული | 한국어 | Kurdî / كوردي | Latina | Lëtzebuergesch | Lietuvių | Bahasa Melayu | Nnapulitano | Nederlands | Norsk (nynorsk) | Norsk (bokmål) | Polski | Português | Română | Русский | Slovenčina | Slovenščina | Shqip | Српски | Svenska | తెలుగు | ไทย | Türkçe | Українська | اردو | Tiếng Việt | Volapük | 中文(简体) | 中文(繁體) | +/-