GB690002A - Improvements in or relating to recording instruments - Google Patents

Abstract

690,002. Electric indicating systems. BRISTOL'S INSTRUMENT CO., Ltd. Feb. 7, 1951, No. 3031/51. Class 40 (i) [Also in Group XIX] In an instrument for recording a plurality of variables, wherein voltages proportional thereto are sequentially balanced automatically in a potentiometer, the recording member is moved by an electric motor responsive to unbalance of the potentiometer and a second motor moves the recording member to effect a marking on a chart, the second motor being delayed in operation until the potentiometer balancing motor is de-energized. As shown, thermocouples 86-88 are connected in turn by a rotary switch 78 to a self-balancing potentiometer 12, 18. The outof balance potential is applied at 32 to a modulator-amplifier 28 the output 33 of which is an A.C., of power frequency, varying in magnitude and phase sense relative to the A.C. input 31 according to the magnitude and sense of the out-of-balance input potential. The modulator output energizes a two-phase induction motor 27 coupled to the slide 15 of the potentiometer resistor 12 which is thereby driven to the balance position. The angular position of the slide is then a measure of the thermo-couple voltage and produces through shaft 16, drum 46 and a cord 47, a corresponding linear position of a carriage 50 along an extended pinion 52. The carriage has a recording type wheel 56 mounted therein. A shaft 65 driven by a two-phase induction motor 72 periodically rocks, through a cam 66, a frame 61 which rocks the carriage 50 about the pinion 52 to bring the operative type 55 of the recording type wheel 56 into contact with the record sheet 41 which is advanced at constant speed. The shaft 65 also periodically steps a shaft 77 through a cam actuated ratchet wheel 93, which advances the switch arm to connect the next thermocouple into the measuring circuit, and by way of gearing 75 rotates the type wheel to bring a new type member 55 into operative position. Shaft 65 also periodically closes contacts 101 connected in series with the contacts of a relay 105 across the phase-shifting capacitor 92 associated with one winding of the motor 72. Relay 105 is energized to close its contacts while the measuring system is unbalanced, and consequently if balance has not been attained when contacts 101 close, motor 72 is stopped until balance is achieved. Alternatively, the motor 72 may be caused to "creep" instead of stopping, thus identifying the thermocouple circuit concerned but not holding up recording indefinitely. Specification 602,460 is referred to.