GB752735A - Electric measuring device for the determination of unbalance values by means of selective rectification - Google Patents

Abstract

752,735. Rotary unbalance measuring apparatus. AVERY, Ltd. W. & T. (Schenck Maschinenfabrik Ges., C.). Aug. 27, 1954 [July 11, 1956], No 24907/54. Class 40(1) Apparatus for measuring the unbalance of a rotor by electrical pick-ups associated with the bearings, feeding into a moving coil ammeter is characterized by a synchronously rotating cam which feeds succesive half-cycles of the signals alternatively into the halves of the centre-tapped meter coil winding so that they produce deflections in the same sense, and the cam also open-circuits the meter winding for a short period in each half-cycle, whereby the effects of all the even harmonics and also the third harmonic are eliminated. As shown, Fig. 1a pick-ups 3 at the bearings feed into the split coil winding of meter 10 yia the contacts of a cam 7 rotating with the test body. Cam section A feeds the signals into one half of the meter coil, section C feeds them into the other half winding, and sections B and D open-circuit the meter coil, the durations A and C being equal, and B and D being equal, with the latter being only half of the former. The angular position of the unbalance is located by rotating the cam contacts to the position of maximum reading on the meter 10. In a modification the pick-ups 3 feed into the whole of the meter coil but the rotating cam short-circuits alternative halves of the coil. Two cam discs displaced by 90 degrees, or one cam with two sets of contacts displaced by 90 degrees, may be used to determine the components of the unbalance mass.