Rotational speed sensor with unfixed and/or fixed edge speed calculation modes

A speed sensor for a rotating body comprising:

• a plurality of teeth attached around the rotating body, the teeth being made of magnetic material;
• a pick-up coil provided separately from the rotating body for generating an electrical signal responsive to a passing of any of the plurality of teeth;
• a signal converter for converting the electrical signal into pulses;
• edge selecting means for selecting either a rising edge or a falling edge of the pulses in a first mode when the speed of the rotating body is lower than a low reference speed and in a second mode when the speed of the rotating body is higher than a high reference speed, the first mode being to select either the rising edge or the falling edge for every pulse monitoring period depending on a relative phase position of the pulses and the pulse monitoring period, and the second mode being to select the one of the rising edge and the falling edge that corresponds to a steeper side slope of the electrical signal generated at the pick-up coil;
• and
• speed calculation means for calculating the speed of the rotating body by measuring a cycle time of the selected edge of the pulses corresponding to the pulse monitoring period.

A speed sensor for a rotating body comprising:

• a plurality of teeth attached around the rotating body, the teeth being made of magnetic material;
• a magnetic pick-up element provided separately from the rotating body for generating an electrical signal responsive to a passing of any of the plurality of teeth;
• a signal converter for converting the electrical signal into pulses;
• edge determining means for determining a rising edge and a falling edge of the pulses for every pulse monitoring period;
• rising edge speed calculation means for calculating the speed of the rotating body based on a time interval and the number of rising edges between the rising edge of a present pulse monitoring period and the rising edge of the previous pulse monitoring period;
• falling edge speed calculation means for calculating the speed of the rotating body base don a time interval and the number of falling edges between the falling edge of a present pulse monitoring period and the falling edge of the previous pulse monitoring period;
• and
• selecting means for selecting the one of said rising and falling edge speed calculation means which corresponds to the edge occuring just before the pulse monitoring period, to provide a speed corresponding to said pulse monitoring period.