GB674034A - Improvements in or relating to liquid level sensitive apparatus - Google Patents

Abstract

674,034. Liquid level measurement; capacitance and inductance measurement; electric condensers. WHEELCO INSTRUMENTS CO. Feb. 24, 1948 [May 3, 1939], No. 5451/48. Class 37. Fig. 1 shows apparatus sensitive to the level 4 of liquid in a container 2, which is connected to a non-metallic gauge tube 6 carrying a pair of separate vertical conductors 7, 8 forming the plates of a condenser, of which the tube and the liquid therein form the dielectric. This condenser tunes the grids inductance 12 of a thermionic oscillator 18, whose anode current is fed through a relay 24 whose moving contact 35 controls the direction of rotation of a reversible split-field motor 30 through an anti-hunting device in which rotary cam 32 closes contacts 34, 38a in the motor circuit at timed intervals and introduces a lag between relay closure and motor operation. The motor drives the shaft of a variable condenser 25 tuning the anode inductance of the oscillator, and also drives a liquid level indicator pointer 26a moving over a dial 26. A level recorder may also be driven by the motor. When the liquid is at a predetermined normal level, the plate circuit is tuned slightly off-resonance with the grid circuit and the constants are such that the anode current holds relay contact 35 neutral between contacts 36 and 37. A change in liquid level alters the grid tuning capacity so as to decrease or increase the difference in tuning between grid and anode circuits, and thus decreasing or increasing the relay current. to close either contacts 35, 37 or 36, 37 depending on the sense of the change, so that the motor retunes the anode circuit with the grid circuit thus restoring the relay contact 35 to neutral; and rotates pointer 26 to indicate the new liquid level. Inductance instead of capacity may be varied by the liquid level, Fig. 2 (not shown). The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 674,113 which is referred to. This subject-matter does not appear in the Specification as accepted.