Patent ID: 7583078

Claim:
A rotation angle detecting device for detecting a rotation angle of a rotating object comprising: magnet field forming means for forming a magnetic field; a Hall element, disposed in the magnetic field to rotate relative to the magnetic field when the rotating object rotates, for outputting voltage according to magnetic flux density of the magnetic field; setting means for setting a temperature characteristic correction value α i (t) at a temperature t for each one of a plurality of grade ranges of the magnetic flux density; a memory for storing the temperature characteristic correction value α i (t) for each one of a plurality of grade ranges of the magnetic flux density; correction means for correcting the temperature characteristic of said Hall element by the temperature characteristic correction value α i (t) that corresponds to a magnetic flux density to detect wherein said setting means sets the temperature characteristic correction value α i (t) in the following steps: measuring the output voltage V 0 and V off (t) of the Hall element under a magnetic flux density of 0 while the ambient temperature is a preset temperature t 0 and a temperature t which changes in a preset range; obtaining ΔV off that is a difference between V off (t) and V 0 ; forming a magnetic field of a certain magnetic flux density B k as one of the grade ranges of the magnetic flux density; measuring an output voltage V out (t) when the magnetic flux density is B 0 ; calculating the magnetic flux density B k from the following expression: B k =(V out (t)−V 0 )/S(t 0 ) wherein S(t 0 ) is an inclination of the output voltage to the magnetic flux density when the temperature is t 0 ; setting the temperature characteristic correction value α k (t) to V sen-off (t 0 )/V sen-off (t) at the magnetic flux density of B k , wherein V sen-off (t 0 )=ΔV off (t 0 )+B k ×S(t 0 ) and V sen-off (t)=ΔV off (t)+B k ×S(t) and wherein S(t) is the inclination of the output voltage to the magnetic flux density when the temperature is t; and setting a temperature characteristic correction value α i (t) at the magnetic flux density being Bi by an expression: V sen-off (t)=(V out (t)−V off (t)) B=Bk ×B i /B k +ΔV off (t).