GB901210A - Manometers or tilt gauges for deriving electrical quantities dependent on liquid levels - Google Patents

Abstract

901,210. Determining liquids levels. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Oct. 6, 1960 [Oct. 6, 1959], No. 33861/59. Class 37. In a manometer or tilt gauge, variation in length of a column or columns of liquid 2, Fig. 1, varies the impedances between two pairs of electrodes 5, 5<SP>1</SP>, 6, 61 forming two arms of a bridge circuit, Fig. 2. The output of the bridge is applied to a calibrated meter. The electrodes may be bare wires immersed in the liquid or may be strips attached to outside surfaces of the tube 1. Alternatively, the tube may be conductive with the other electrode arranged centrally within it. In one embodiment, a manometer may have an additional U tube secured to it so that the latter serves to replace the bridge resistors R 3 , R 4 can thus compensate for errors due to the tilting of the manometer. In another embodiment, the output voltage from the bridge of the first manometer is fed to the input terminals of a bridge for a second manometer, the latter being subjected to corresponding pressures. The output from the second bridge then varies according to the square of the pressure difference, this procedure may be repeated to produce the cube of the pressure difference. In another arrangement for producing a signal varying with the square of the pressure difference, the frequency of the output voltage from the bridge is modified and the resultant signal fed back into the input of the bridge, the new output voltage being measured after selection by a frequency responsive circuit.