GB609508A - Improvements in or relating to transmitters for liquid level measuring devices - Google Patents

Abstract

609,508. Electric indicating systems. LIQUIDOMETER CORPORATION. Jan. 15, 1946, No. 1356. Convention date, Sept. 8, 1945. [Class 40 (i)] In a transmitter for a liquidlevel measuring device, a partly immersed member is caused to vibrate by an electrical oscillating means at a frequency a function of the liquid level. In the embodiment shown, the metal bar 3 is supported at 4 in the vessel 1 containing liquid to the level 2 and urged to a central position at its upper end by the springs 5. The rod 7 is attached to the bar at right-angles at 6 and supports the ferromagnetic plunger 9 and permanent magnet 8 inside the guiding enclosure 10 of non-magnetic, lowconductivity material. Coils 11 and 12 surround the plunger 9 and magnet 8 respectively, the former being connected in the circuit of anode 19 of valve 21 and the latter between the grid 16 and cathode 20. After switching-on, the plunger 9 is drawn into coil 11 and causes the member 3 to move to the right and the magnet 8 to be displaced within coil 12. The voltage thereby generated at grid 16 is such as to reduce the anode current and the member 3 is then moved to the left, by the springs 5, beyond the central position. During this motion the voltage at grid 16, due to the action of coil 12 and magnet 8 is such as to raise the current through coil 11 and the cycle is repeated at a frequency determined by the natural frequency of vibration of the member 3 which is a function of the liquid level 2. The frequency of the oscillator 13 is determined by device 14, the output of which operates indi. cating device 15, suitably calibrated. In a further embodiment, not shown, a magnetic vibrating member is maintained in motion by a magnet energized by the anode circuit of a valve, the grid of which is supplied with an A.C. voltage from a condenser, one plate of which is fixed and the other is formed of a section of the member.