In harsh environments where non contact speed sensing and control are required, for example to control the slip of a.c. induction motors, the measurement resolution is usually derived from the number of gear teeth or target pole pieces. This can lead to large and heavy gears being used for no other purpose than to provide speed data. The new X8 sensor from Swiss based JAQUET TECHNOLOGY GROUP alleviates this problem by providing frequency out as 2 phase shifted speed signals = 8 times the number of teeth – right from the first tooth detected. Space and weight can then be saved through the dimensioning of smaller pole wheels.

Internally the X8 sensor uses Hall Effect elements, which measure the change in magnetic field that is generated by the gear rotation. The signals generated are interpolated in such a way that 8 pulses per tooth are generated, e.g. for a pole wheel with 128 teeth there will be 1024 impulses per revolution. Currently the sensor works for pole wheels down to a module of 1mm. The sensing elements and electronics are potted into a fully sealed housing with the phase shifted signals driven from push-pull outputs. By externally combining the 2 phase shifted signals the speed resolution can be even further increased by a factor of 4.

Available in various housing sizes , X8 sensors operate over a wide voltage range of 10…30Vdc and have been type tested for demanding applications such as railway traction control. Other applications includepulp and paper industry machinery, hydraulic systems and motor control.