Patent GB-192122-A (GB)
Title: A device for indicating and/or recording movements or expressions of physical values or effects
IPC: H01J40/00
Filed: 1921-09-26
Abstract: 192,122. Roucka, E. Sept. 26, 1921. Tell-tale apparatus.-Relates to indicating and like systems of the kind in which the primary measuring instrument alters the effect of a ray of energy on a sensitive device, and the latter controls an auxiliary power so as to restore the original conditions and at the same time to give an indication or record. (1) In the arrangement shown in Fig. 1, a beam of light is reflected by a mirror 2 equally on to two selenium cells 5, 6 forming two arms of a Wheatstone bridge and mounted on a pivoted member 7.. Movement of the mirror 2, which forms part of a measuring instrument, unbalances the bridge and the tongue of relay 17 causes rotation of the motor 14 in one or other direction. Motor 14 through gearing moves member 7 to restore the balance of the bridge and to give an indication on the scale 9. At the same time, resistance is cut in or out of a circuit containing an indicating device 27 and an integrating device 28 which may be at a distance. (2) In another form, Fig. 2. the sensitive. device 39, shown as a pair of thermo-couples, is fixed and the measuring instrument of which the mirror 30 forms a part is carried by the pivoted body 33. Movement of mirror 30 causes operation of a differential relay 42. which controls the supply of fluid to a motor 38 of which the member 47 moves the member 33 until the tongue of relay 42 returns to the mid-position. At the same time a cam 49 moves the brushes of a constant speed dynamo so that an indication is given on the instrument 54. (3) In the system shown in Fig. 3, an electrostatic voltmeter has stationary plates 56, 57 across which is connected the poten. tial to be measured and movable plates 58, 59 suspended by a filament which also carries a mirror 61 and astatically mounted magnets 62, 63. Deflection of mirror 61 controls as in the previous examples, the operation of a fluid motor 73 which cuts resistance in to or out of an electric circuit. This circuit includes coils 82, 83 which act on the magnets 62, 63 so as to restore the mirror to its normal position, and also indicating, recording, and integrating devices 81, 80, 79 and a relay 78 which may be at a remote situation. (4) In the system shown in Fig. 4, a pressure gauge for low pressures comprises, a heated filament 87, Fig. 5, and a strip 88 which is deflected by molecular bombardment to an extent corresponding to the pressure in a vessel connected to the apparatus by the tube 86. The strip 88 carries a shutter 89 adapted to cut light off from one of a pair of selenium cells and so to control a fluidpressure device 96 which operates a similar shut. ter 97 to cut light off from the other cell and to move a pointer over a scale. (5) In a further system, light is reflected from the surface of mercury in a manometer tube, or if mercury is not used, from a reflecting float, on to pair of selenium cells. Alterations in level of the liquid control the rotation of an electric motor which through gearing raises or lowers the manometer to restore the original conditions, the extent of the movement being indicated by a pointer. (6) In the system shown in Fig. 8, mercury in a thermometer 119 bent as shown cuts off more or less light from a selenium cell, thus controlling an electric motor 128 which through gearing rotates the thermometer to restore the original conditions. An indication is given by a pointer 121 carried by the thermometer. (7) A further method of restoring the beam to its original state with respect to the sensitive device consists in causing the auxiliary power to move a prism situated between the source of light and the mirror.