GB803069A - Improvements in fluid flow meter sensing units - Google Patents

Abstract

803,069. Driving dynamos. SIMMONDS AEROCESSORIES, Ltd. Aug. 13, 1956 [Aug. 19, 1955], No. 23962/55. Class 35. [Also in Groups XXVI and XXXVIII] A pick-up unit for a fluid - flow meter comprises a straight section of pipe of non - magnetic material containing a balanced bladed rotor of magnetic material which is rotated about a longitudinal axis by the fluid flow so that the blades come simultaneously opposite one or more pairs of polepieces secured to the pipe, these polepieces being linked to a common permanent magnet (or D.C. excited coil) by a yoke of soft magnetic material; one or more sensing coils mounted on the polepieces generates an E.M.F. when the magnetic circuit is completed by the rotor blades. In the simplest arrangement (Fig. 1) the magnetic circuit comprises the rotor blades 5 within the pipe 2, and the polepieces 6, 7, yoke 10, 11 and magnet 12, impulses being generated in the coils 13, 14 when the blades come into the position shown. In modifications (Fig. 3, not shown), a second pair of coils is mounted 60 degrees away from the first pair and connected so that the E.M.F's re-inforce each other; (Fig. 4, not shown) a six-bladed rotor has four coils so that four blades come simultaneously opposite to them; (Fig. 5, not shown), four pole-pieces successively 30 degrees apart are used, with a six-bladed rotor, the middle pair only being provided with coils. It is stated that it is possible to have only one sensing coil per pair of polepieces. In certain of the above arrangements pairs of coils may be connected so that the signals neither re-inforce nor cancel each other, e.g. if the phase difference is 90 degrees, and in this case the output is a ripple superimposed on steady D.C.