Patent GB-893830-A (GB)
Title: Improvements in gyroscopic mass flowmeters
IPC: G01F1/84
Filed: 1960-04-19
Abstract: 893,830. Gyroscopic mass flowmeters. ROTH, W. April 19, 1960 [Feb. 2, 1960], No. 13637/60. Class 40 (1). Fluid flows through a loop conduit which is oscillated about a drive axis thereby producing gyroscopic torque couples which generate an A.C. signal in a " velocity type " generator, which signal may be passed through an integrating circuit to reduce or to eliminate the drive frequency amplitude factor so that the resultant signal is accurately proportional to - the rate of mass flow in the conduit. Alternatively the output signal may be algebraically combined with a reference signal to eliminate the drive frequency factor in each. Other extraneous signal components may be eliminated by filtering or by use of two transducers in a series aiding arrangement whereby the signals are subtracted. Construction.-As shown, the fluid flows in a hollow annulus 10, Fig. 1, carried by a member 15 and rocked about a vertical axis by a motor 24 with the aid of a shaft 21, 18, 18<SP>1</SP> which also carries the permanent magnet field systems 32, of a pair of transducers 19, 19<SP>1</SP>. The resulting gyroscopic torque causes the annulus to rock about a horizontal axis against the restoring torque provided by reduced portions 17, 17<SP>1</SP> of member 15 with the result that an alternating voltage is generated in the transducer windings which are carried by the annulus. In a modification, Fig. 4 (not shown), the drive-shaft 21 is bolted to a stationary base through a narrow section which acts as a torsional restoring spring assisting the oscillation. The moment of inertia of the loop is chosen to give resonance near the drive frequency thereby reducing the motor power required. Circuit arrangements.-The voltage generated by the transducers, which are connected in series, is proportional to the product of mass flow and the square of the frequency and various curcuits are described for eliminating the effect of frequency. As shown, in Fig. 5, the frequency factor is eliminated by integrating the signal twice at 41, 42. The resulting signal is then rectified by a synchronous commutator, smoothed, and operates a D.C. meter. In another arrangement, Fig. 6 (not shown), the signal is measured by a self-balancing potentiometer supplied, by differentiating the output of an alternator driven by motor 24, with a voltage varying as does the signal in accordance with the frequency squared. In another arrangement, Fig. 7, a synchronous rectifier 61 produces a D.C. output proportional to the pick-up signal and this is divided in apparatus 64 by a signal representing the square of the frequency factor obtained by differentiating and rectifying a reference signal. In another arrangement, Fig. 9 (not shown), the pick-up signal and reference signal are respectively differentiated and integrated or vice versa and then multiplied or divided without previous rectification. In a final arrangement, Fig. 10 (not shown), a reference voltage is derived from transducers operated by the rocking of the annulus about its vertical axis and since this voltage varies with the square of the frequency no differentiating or integrating operation for either signal or reference voltage is called for, and simple division of the two voltage signals will eliminate the frequency factor.