Abstract: Apparatus responsive to the pressure of a fluid contained in or surrounding a stiff but resilient hollow body comprises a stiff, but resilient ring mounted concentric with the body by means of four equi-spaced radially extending stiff struts. Electromagnetic means is provided for exciting natural vibrations of the ring at a resonance frequency, which will be dependent upon the pressure of the fluid in the body. Means is provided for measuring the frequency of vibration, enabling the pressure of the fluid to be determined, e.g. from a pressure-frequency calibration curve for the apparatus.

Abstract: A method of interpolating a value of the dependent variable, y corresponding to a given value of an independent variable x, wherein y = f(x) and is described by a linear polynomial series of the 8'th order. The method uses a 4'th order polynomial interpolation method to obtain up to an 8'th order interpolation in 2 iterations of the 4'th order method. The method is suitable for implementation by a computer or by purpose-designed data processing apparatus. An embodiment of apparatus suitable for use in performing the method is also disclosed.

Abstract: Apparatus for determining the density of a liquid comprises a resilient tube coupled at each end through resilient couplings to support flanges for connection in a pipeline or the like. Two cantilevers of the same material and cross section as the tube are secured to the tube so that they have a common axis parallel to that of the tube and their free ends are directed towards each other. The tube and cantilever are so excited that they vibrate in antiphase at the same transverse frequency of vibration, the frequency of the vibration being dependent upon the density of liquid in the tube. The cantilevers are provided with an annular collar at their free ends such that when the tube is filled with a liquid of a predetermined density the root shear force and bending moment of each cantilever cancels those of the tube.