GB848238A - Electromagnetic thermometer - Google Patents

Abstract

848,238. Electric measuring systems. VYZKUMNY A ZKUSEBNI LETECKIJ USTAV. Oct. 11, 1957 [Oct. 11, 1956], No. 31821/57. Class 40 (1). In temperature-measuring apparatus, a ferromagnetic body is magnetized by A.C. and is subjected to torsional stress owing to the expansion of a member or a fluid exposed to the temperature to be measured, the consequent distortion of the magnetic field inducing a signal representative of the temperature in a pick-up coil wound on the body. As shown, Fig. 1, a cylindrical jacket 1, provided with helical slots 2, is disposed around a ferromagnetic body 3, being fixed thereto at both ends and in the middle. The jacket 1 and the body 3 have different co-efficients of thermal expansion, so that a temperature change causes the body to be twisted, distorting the field produced by a toroidal excitation winding 5 and generating an E.M.F. in pick-up coils 4. Fig. 2 depicts a device for measuring surface temperature in which a change of dimension of a base 6 transmits a torsional stress to a body 11 secured centrally to one end of the base 6 and at its ends to a casing 9, which is itself attached to the other end of the base. Parts of the device remote from the base are protected by thermal insulation 16. In the device shown in Fig. 4, the expansion or contraction of a rod 17 relative to its casing 18 is transmitted to a ferromagnetic body 22 via a rod 19 and a lever 21. To measure temperature at a relatively inaccessible point, the change in volume of a fluid 28, Fig. 5, in a vessel 27 subjected to the temperature operates, via a capillary tube 29 to modify the shape of a corrugated vessel 30, thus twisting a currentcarrying ferro-magnetic body 32 centrally fixed on the vessel 30 and wound in the form of a twostart helix and carrying a pick-up coil 33. In all embodiments, the exciting and pick-up circuits may be interchanged.