Berechnung eines Wertes aus Widerstandsreihe

[_frank_]

so funktioniert es fast...

Delphi-Quellcode:

FUNCTION FindValue(reihe:byte; wert:integer):integer;
const
  //r3:array[0..2] of double=(1.0,2.2,4.7); //2^0
  //r6:array[0..5] of double=(1.0,1.5,2.2,3.3,4.7,6.8);//2^1
  //r12:array[0..11] of double=(1.0,1.2,1.5,1.8,2.2,2.7,3.3,3.9,4.7,5.6,6.8,8.2); //2^2
  r24:array[0..23] of integer=(100,110,120,130,150,160,180,200,220,240,270,300,330,360,390,430,470,510,560,620,680,750,820,910);//schrittweite 8 (1,9,...) =>E3 2^3
  r192:array[0..191] of double=(
    100,101,102,104,105,106,107,109,110,111,113,114,115,117,118,120,121,123,124,126,127,129,130,132,133,135,137,138,140,142,143,145,147,149,
    150,152,154,156,158,160,162,164,165,167,169,172,174,176,178,180,182,184,187,189,191,193,196,198,
    200,203,205,208,210,213,215,218,221,223,226,229,232,234,237,240,243,246,249,
    252,255,258,261,264,267,271,274,277,280,284,287,291,294,298,
    301,305,309,312,316,320,324,328,332,336,340,344,348,
    352,357,361,365,370,374,379,383,388,392,397,
    402,407,412,417,422,427,432,437,442,448,
    453,459,464,470,475,481,487,493,499,
    505,511,517,523,530,536,542,549,
    556,562,569,576,583,590,597,
    604,612,619,626,634,642,649,
    657,665,673,681,690,698,
    706,715,723,732,741,
    750,759,768,777,787,796,
    806,816,825,835,845,
    856,866,876,887,898,
    909,920,931,942,
    953,965,976,988
  );
var first,last,actual,step:integer;
    found:boolean;
begin
   first:=0;
   last:=(3 shl reihe)-1;
   step:=1 shl (7-(reihe+4));
   found:=false;
   actual:=-1;
   while not found and (first<=last) do
   begin
     actual:=(first+last) shr 1;
     if r24[actual*step]<wert then
       first:=actual+1
     else
       last:=actual-1;
   end;
   if first>((3 shl reihe)-1) then
     result:=r24[0]*10
   else
     result:=r24[actual*step];
end;

nur wenn der schleifenstartwert (bei e6 220=actual 2) der richtige wäre, ist das Ergebnis falsch. z.B.
showmessage(IntToStr(findValue(e6,215))); gibt mir nicht 220 sondern 150, das dieses der nächst-tiefere wert ist.

Wie könnte man das lösen?