GB626787A - Improvements in and relating to electrical recording instruments - Google Patents

Abstract

626,787. Recording-apparatus. DAVIS, N. R., and SUN-VIC CONTROLS, Ltd. May 16, 1947, No. 13276. [Class 106 (iv)] [Also in Group XXXVIII] Apparatus - for recording several variables comprises electrodes associated with an electrically-sensitive chart base, one of which electrodes forms a stylus electrically operated by the measuring element and switching means controlling the application of voltage to the stylus for modifying the voltage periodically in a synchronous relation with the commutation of the connection of the measuring element between circuits for the several variables so as to produce distinctive indications on the respective curves. A recording instrument 1 operates a stylus 2 co-operating with a chart 3 wound over a drum 4 driver at constant speed by an electric motor or clockwork 5 through a gear train 6, 7, 8. To record several variables such as voltage from three thermocouples, one side of each is connected through terminal 9 to one side of the instrument 1, while the other sides are connected through terminals 10, 11, 12 to fixed segments 13, 14, 15 of a commutator which has a moving brush 16 driven by the motor 5 and connected through a slip ring 18 and co-operating brush to the other side of the instrument 1. A source of voltage sufficient for recording is connected through a terminal 32 to the stylus 2 and through a terminal 31, slip ring and brush 30 and brush 19, driven with the brush 16, and thence through one of three contacts 20, 21 22 to an appropriate brush 23, 24, 25 and disc 26, 27, 28, through shaft 29, driven at a fraction of the speed of the brushes 16, 19, to the chart drum. The brush 19 co-operates with a contact when brush 16 nears the end of a segment, thus allowing the stylus 2 to settle before the recording circuit is completed. The discs 26, 27, 28 have insulating segments 33, 34, 35 offset which cause interruptions in the three records at different times to characterize them according to a code determined by the arrangement of insulating segments. In a second embodiment an auxiliary stylus applies a marking code to the curves which are not interrupted. The stylus 2 is connected to the contacts 20, 21, 22, whilst the drum 4 is connected to the terminal 32 through earth. The terminal 31 is also connected to a further brush moving with the brush 16 and cooperating successively with three contacts connected respectively to the brushes 23, 24, 25 which intermittently complete a recording circuit through isolated contacts carried by the discs 26, 27, 28 which are now of insulating material, the contacts being arranged according to the marking code. In a third embodiment the chart 3 is of a material in which the colour or thickness of the mark produced depends on the magnitude of the applied voltage. The stylus 2 is connected through the slip ring 30 to the brush 19 and the contact 20 is connected to the terminal 32, the contacts 21, 22 to tappings in a potential dividing resistor between the terminals 32, 31, the latter being connected to the drum 4.