Patent GB-244195-A (GB)
Abstract: 244,195. Shotter, G. F. Sept. 23, 1924. Tell-tale apparatus.-In apparatus for indicating electrically the level or flow of fluids, the pressure of gases, or the height or movement of a body such as a gasometer and employing apparatus of the type comprising a pair of main electrodes immersed in liquid and a pair of compensating electrodes for neutralizing polarization effects, the distance between the main electrodes and consequently the resistance of an indicating circuit is varied in accordance with the level &c. to be measured. As shown in Fig. 1, a vessel 1 is divided by partitions 2 to form a U-tube one leg of which contains the anode 8 of the compensating electrodes and the other leg contains the anode 9 of the main electrodes. A cathode 12 common to the anodes is arranged at the bottom of the U-tube. The electrodes are made of wire or gauze mounted on frames. The anode 9 is immersed in liquid, which may flow continuously through the U-tube, and is connected to a float 11 in the liquid whose height or flow is to be measured. The compensating electrode 8 is connected to the coils 13, 14 which provide the control of a resistance indicator, while the main electrode 9 is connected to the coil 16 which provides the deflecting force, so that the indicator gives indication of the positions of the electrode 9 independently of the E.M.F. of polarization. In a modified form of electrode containing vessel, a compartment is provided for each electrode. In a further modification the container for the electrodes comprises a tube, with the common cathode 12 mounted between the main and cornpensating anodes 8, 9. The variations of liquid level or other movements to be measured may be communicated to the main anode through the intermediary of cams or gearing. The apparatus may also be used for indicating the variations of flow through pipes. In this case, the pressures derived from a Venturi meter, Pitot tubes, or from each side of a restriction in the pipe act differentially on the anode 9. A Bow'den gauge or aneroid chamber may be connected to the main anode to adapt the apparatus for the indication of gas pressures. Fig. 9 shows a modified form of apparatus for indicating the variations in gas pressure. A vessel 3 has four compartments 24 in which are contained the anodes 8, 9, the common cathode 12, and in addition a further anode 48 carried on a float 49. The anode 48 is so connected to the indicator that allowance is made for variations in the level of the liquid in the vessel whicn are not due to variation in gas pressure. The gas is introduced through a conduit 50 and the pressure causes the liquid in the compartment to vary the position of a float 47 which carries the anode 9. In a further modification, the common cathode and compensating anode, may be mounted on a carrier which is fixed in the liquid whose height or flow is to be measured, and the main anode may be mounted on a float so as to move relatively to the common cathode. Instead of a common cathode, a common anode and separate cathodes may be employed. In addition separate cathodes may be employed for the anodes and the compensating electrodes may be arranged in a separate vessel which contains liquid of similar polarizing properties to those of the liquid in which the main electrodes are immersed. A system of guard wiring may be employed for preventing the measurement of leakage currents. Specifications 17044/11 and 163,739, [Class 38 (v), Electric switches &c.], are referred to.