Patent GB-616538-A (GB)
Title: Improvements in and relating to bolometer type telemetric systems
IPC: G08C19/38
Filed: 1945-10-22
Abstract: 616,538. Electric follow-up systems; telemetric systems. JACK & HEINTZ, Inc. Oct. 22, 1945, No. 27766. Convention date, Nov. 25, 1944. [Class 40 (i)] [Also in Group XL (b)] In a telemetric system for operating a selfbalancing indicating or servo-mechanism without loading the primary element, a movable shroud operable by the latter controls the heat falling on a pair of bolometer elements from their corresponding heaters, the elements being connected in a bridge circuit whereby member carrying the elements and their heaters is operable to follow the shroud movements to keep the system balanced. In Fig. 1, a shaft 1 which may be operable by the indications of a magnetic compass, gyro device, or similar mechanism, carries a semi-cylindrical shroud 2 separating heater elements 12, 13 from bolometer elements 14, 15; such elements being carried by a follower table 7 axially aligned with the shroud and rotatable by a two-phase motor 26, energized by the A.C. supply 20 through a condenser 27 and by the output of an amplifier 25 of the type shown in Fig. 2 whose input is connected to a diagonal 23, 24 of the bridge 14, 15, 17, 18, 19, the other diagonal being connected to the A.C. supply. In the balance position, the shroud interrupts half the radiation flow to each bolometer from its heater, and the bridge is balanced by adjustment of tapping 23 so that no voltage appears across diagonal 23, 24. Rotation of shaft 1 causes unequal heating of the bolometers, unbalance of the bridge, and the supply of an alternating voltage from the amplifier to the motor, the phase of which depends on the sense of the shaft rotation. The follower table is rotated by the motor in such a direction as to re-balance the bridge by equalisation of the radiation falling on each bolometer, when movement ceases. The system may control a known self-synchronising remote indicator 30 which is energized by the supply and by three tappings spaced 120 degrees apart on a resistively or inductively wound ring 33 connected to the supply through two diametricallyopposed contact fingers 31, 32, carried by the follower table. In a modification (Fig. 4, not shown), the system is operated from a D.C. supply. The amplifier 25 is replaced by a sensitive polarised two-way D.C. relay 40, controlling the direction of energization of a split-field D.C. motor 41 driving the follower table, the ring 33 being resistively wound and the indicator 30 being of the known polarised or permanent magnet type. In a further modification (not shown) a signal may be derived from the fingers 31, 32 whose magnitude is proportional to angular rotation of the follower table and whose phase or polarity indicates the sense of rotation. In other modifications (not shown) the bridge may be D.C. excited and the motor A.C. driven through a control relay, a disc-type shroud may be employed, which may be eccentric, or the heaters and bolometer elements may be enclosed in evacuated tubes. The bridge resistors 17 and 18 mav also be bolometer elements and the amplifier 25 is replaceable by thyratron or saturable reactor control means. The system is stated to be also applicable to translatory motion.