Patent GB-1240314-A (GB)
Title: Device for supervising at least one physical value
Inventor: SOLVAY JEAN
IPC: A61B5/044
Filed: 1968-11-18
Abstract: 1,240,314. Photo-electric reading apparatus. J. SOLVAY and H. SOLVAY. Nov. 18, 1968 [Nov. 21, 1967], No. 54680/68. Heading G1A. In the monitoring of a cyclically varying physical characteristic e.g. an internal combustion engine operating characteristic, or the cardiac rhythm of a living creature, each cycle or part of each cycle of the characteristic is represented by an electrical signal which is displayed as a point or a broken curve on the screen of a cathode ray tube. The screen is viewed by a photo-cell through a mask having a slit, shaped to correspond to a normal cycle for the physical characteristic and if parts of the displayed electrical signal are not in alignment with the slit, an output from the photo-cell circuit is obtained indicating that an abnormal cycle has occurred. In the arrangement of Fig. 1, the horizontal (X) deflection plates 5 of C.R. T. 1 are supplied by a sawtooth waveform and the vertical (Y) plates with the electrical signal representing the physical characteristic to be studied. The Wehnelt grid 3 is supplied by a 1000 c/s pulse generator, so that the electrical signal is displayed as a series of points 21 on the screen forming a curve representing one cycle of the physical characteristic. The slit 20 in baffle 10 defines the shape of a normal cycle. When points 21 are seen by photo-cell 11, pulses are amplified at 12, and trigger flip-flop 13, to feed an exclusive-OR gate 14. However, at these instants no output will be produced from gate 14 since they are coincident with pulses arriving from generator 15. Only when there is no output from the photo-cell 11, are pulses passed by gate 14 from the generator 15. These correspond to section B in Fig. 2 which shows an abnormal cycle. An alarm or visual indicator, or a threshold integrator device giving an output when integrated missing pulses exceed a predetermined count, can be connected to gate 14. The slot may have a varying width so providing a varying tolerance for the physical characteristic throughout the cycle. With a second arrangement, Figs. 5, 6 (not shown) it is possible to examine only a small part of a cycle by expansion of that part of the cycle to fill the screen. It is necessary to use two electron beams, slit and photo-cell systems, one acting as a reference system for generation of reference pulses and the other producing pulses when the electrical signal is following the normal curve. An exclusive-OR circuit is again used. A number of different physical characteristics can be monitored by providing a plurality of electron beams and of slits in the screen. Particular sections only of a waveform may be investigated by blocking sections of a slit. In the arrangement of Fig. 8 (not shown), the Y deflection plate is provided with a pulse supply of lower frequency than that of the Wehnelt grid which causes the points periodically to jump from one side of the slot to the other. The photo-cell pulse output thus varies in amplitude in accordance with variations of the displayed waveform from the normal curve defined by the slit, and is analyzed by detector and demodulator circuits. In the arrangement of Fig. 10 (not shown), the points are caused to describe a periodic circular path, the detector circuit in this coil including a detector circuit, feeding an AND gate which also receives the output of the generator causing the circular movement, via a threshold device. A further arrangement, Fig. 13 (not shown) is provided with selection means to allow display of predetermined sections of the cycles of a number of different physical quantities, there being provided a single slit and photo-cell which feeds via an exclusive OR circuit, a selector switch to select corresponding indicators for each physical quantity. This arrangement may be modified to allow display of vertical broken lines one for each physical characteristic, Fig. 15 (not shown), so that the value of the characteristic with respect to the tolerated values (defined by the weight of the slit can be monitored, the exclusive-OR circuit being replaced by a counter.