Contactless magnetic temperature sensors for turbo-molecular pumps

Sensors and Actuators A 153 (2009) 212–217

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Contactless magnetic temperature sensors for turbo-molecular pumps O. Bottauscio a,∗ , M. Chiampi b , G. Crotti a , F. Fiorillo a , S. Giors c , G. Pittà c , C. Quartarone c a

Istituto Nazionale di Ricerca Metrologica, Torino, Italy Dipartimento di Ingegneria Elettrica, Politecnico di Torino, Torino, Italy c Varian S.p.A., Leinì (TO), Italy b

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Article history: Received 8 January 2009 Received in revised form 12 March 2009 Accepted 15 May 2009 Available online 27 May 2009 Keywords: Contactless thermal sensors Magnetic materials Turbo-molecular pumps

a b s t r a c t A magnetic sensor for non-contact measurement of the temperature of a spinning device is studied in the present work. This sensor specifically applies to the control and safe operation of turbo-molecular pumps. The sensing element consists of a “magnetic capsule”, composed of a quasi-ideal permanent magnet with high Curie temperature and a Fe–Ni alloy cylinder, mounted on the rotor, and a detecting coil stuck on the pump frame, where a voltage pulse is induced at every turn by the passage of the capsule. It is demonstrated that the sensor can be designed so as to have a linear voltage-versus-temperature behaviour, where the signal strength depends on the distance between the revolving magnet and a fixed pickup coil and is independent of rotor speed. © 2009 Elsevier B.V. All rights reserved.

1. Introduction Turbo-molecular pumps (TMP) are the most reliable and cost-effective means of producing ultra-high-vacuum conditions (