TESTING SYSTEM

To allow rotational speed in a low rotation speed area to be measured by adding a simple structure.SOLUTION: Four magnetic sensors 7 are arranged around a rotary disk 5 that rotates together with a revolving shaft of a dynamometer 1 and has many teeth arranged in a circumferential direction so that four detection signals, A*, B*, A∼*, B∼*, whose phases are shifted at 90 degrees are detected. A=A*-A∼*, B=B*-B∼*, θ1=atan2(B,A), θ2=atan2(-A,B), ω1=dθ1(t)/dt, ω2=dθ2(t)/dt are calculated, ω1 and ω2 are selectively used as ω so that ω1 during a period when θ1 changes from +π to -π and ω2 during a period when θ2 changes from +π to -π are not used and, with the number of teeth of the rotary disk 5 as n, the rotational speed ωd1 is calculated by ωd1=(ω/n)×(60/2π).SELECTED DRAWING: Figure 2 【課題】簡易な構成の付加により低回転速度域の回転速度を計測可能とする。【解決手段】ダイナモメータ１の回転軸と共に回転する、周方向に並んだ多数の歯を有する回転盤５の周囲に、順次位相が９０度ずれた４つの検出信号A*、B*、A~*、B~*が検出されるように４つの磁気センサ７を配置する。A=A*-A~*、B=B*-B~*、θ1=atan2(B,A)、θ2=atan2(-A,B)、ω1=dθ1(t)/dt、ω2=dθ2(t)/dtを算出し、θ1が+πから-πに変化する期間のω1と、θ2が+πから-πに変化する期間のω2を用いないように、ω1とω2を選択的にωとして用い、回転盤５の歯数をｎとして、回転速度ωd1を、ωd1=（ω/ｎ）×（60/2π）により算出する。【選択図】図２