Abstract: There is disclosed apparatus for sensing cyclically varying pressure in a pipe, particularly but not exclusively for sensing pressure in fuel lines. The apparatus depends on resilient elements which bend symmetrically on pressure change, and transducers producing equal and opposite signals depending on the bending strain. In the first form of apparatus, a ring surrounds the pipe and bears upon it through screws at four spaced points. The ring is on two portions, to be assembled around the pipe. When so assembled, the ring portions bend as beams when the pipe dilates. Symmetrical piezoelectric crystals detect this bending. The second form of apparatus described comprises a pair of similar sensing members in the form of blocks each shaped to embrace a pipe over an arc and to make line contact with the pipe at two spaced locations; the blocks are removably clamped about the pipe.

Abstract: A pressure sensing device comprising a ring surrounding or adapted to surround a body subjected to internal pressure; means to connect the ring physically to the body at spaced locations, the connecting means transmitting to the ring dilation and contraction movements of the body due to variation of pressure therein; said movement transmitted by the connecting means causing a portion of the ring between adjacent spaced locations to flex elastically in the manner of a bending beam, and an electrical transducer mounted upon said flexing portion of the ring, to produce electrical signals dependent on the pressure variation. One form of the device is adapted to clamp around an engine fuel line to sense fuel pressure. Another form of the device is adapted to measure engine cylinder pressure. In a further development of the invention these two forms of device are combined to feed information to engine analysing circuitry producing a visual display.