Patent GB-1178691-A (GB)
Title: Improvements in or relating to Electrical Analogue Computers
Inventor: WALKER JOHN
IPC: G06G7/22
Filed: 1966-03-08
Abstract: 1,178,691. Field artillery analogue computers. SPERRY RAND Ltd., and DEFENCE, SECRETARY OF. 27 Feb., 1967 [8 March, 1966], No. 10007/66. Heading G4G. In a field artillery computer, also applicable to navigation and survey, a bridge circuit (Fig. 1, not shown) comprises a symmetrical potentiometer having two ganged sliders adjustable in accordance with the range R of a target from a gun position, energizing a symmetrical sin-cos potentiometer having two sliders adjustable in accordance with the bearing of the target from the gun, which develop signals representing R sin #, R cos # which are compared in centre zero switchable sensitivity meters with signals from symmetrical potentiometers representing at balance the northing and easting cartesian co-ordinates of the target relative to the gun, given by R sin #=E R cos #=N. (Fig. 2, not shown). The potentiometers have interconnected centre taps and clutchable read-out indicators, and are switchably energized from a symmetrical D.C. source. If the target has range r and bearing # from an observation post (Fig. 3, not shown), these parameters may be set into the computer, and adjustment for balance gives the cartesian coordinates of the target relative to the OP, after which the read-out indicators of the balance potentiometers may be declutched and reset to the map reference of the OP; then clutched and reset to the map reference of the gun. The range and bearing potentiometers are readjusted to balance the bridges, so that they indicate the range and bearing of the target from the gun. In a more developed apparatus, observed firing corrections may be introduced. The target T (Fig. 4) bears # at range r from the observer at O, and # at range R from the gun, while the northing and easting errors of the fall of shot are - #N and - #E, so that #N = C AL  cos # - C AC  sin # #E=C AC  cos #+C AL  sin # where C Ac  is a required correction transverse to the observer's line of sight. C AL  is a required correction along the observer's line of sight. In Fig. 5, a bridge circuit energized over switch 3 from D.C. supply 2 comprises independent adjustable potentiometers 4, 5, 6, 7 clutched to read-out counters indicating respectively R, #, N and E, with a pair of centre zero balance meters 8, 9 having series resistors 10, 11 connectible by sensitivity switches 12, 13 and capacitors 14, 15 effective to flick each meter needle when the sensitivity switches are operated on unbalance. Potentiometer 4 is energized over preset resistors 16, 17. The sin/cos sliders of potentiometer 5 energized from potentiometer 4 are connected to the unbalance meters 8, 9, which are respectively returned to sliders of potentiometers r 2 , r 3  of series networks 27, 28. Two pairs of double centre-tapped potentiometers 19, 20, 21, 22 are D.C. fed from separate rectifiers 33, 34, 35, 36 transformer energized from balanced transistor relaxation oscillator 43, 44 energized from the D.C. source, and potentiometers 19, 21 are ganged together with centre taps returned to the centre of network 27 while potentiometers 21, 22 are ganged together with centre taps returned to the centre of network 28. A four-wafer switch 23, 24, 25, 26 has 24 positions calibrated for different values of # over a range of 2# and four corresponding sets of switchable resistors connected between the output contacts of the switch and the resistors r 1 , r 4  of networks 27 and 28 respectively. The sliders of potentiometers 6, 7 are connected to the slider of r 3  in network 27 and r 2  in network 28, while the inputs of switches 23, 24, 25, 26 are energized from the sliders of potentiometers 19, 20, 21, 22 respectively. Potentiometers 19, 21 are set to CAL and potentiometers 20, 22 to CAC, while the switchable resistors are proportioned so that networks 27, 28 receive voltages representing CAL sin #, CAC cos #; CAL cos #, CAC sin # on their respective ends, so that between the sliders of r 2 , r 3  voltages appear representing CAL cos # - CAC sin # CAC cos # + CAL sin # proportionate to #N, #E respectively. The sliders of r 2 , r 3  are adjusted so that the voltages correspond to the analogue calibration of the bridge and introduction of the correction signals of the combination with the northing and easting signals of the target produces a further unbalance, which is removed by adjustment of potentiometers 4, 5 to indicate corrected range and bearing of target from gun.