Patent GB-762537-A (GB)
Title: Improvements in or relating to apparatus for determining the function of two independent variables
IPC: G06J1/00
Filed: 1954-06-15
Abstract: 762,537. Digital electric calculating-apparatus. SCHLUMBERGER WELL SURVEYING CORPORATION. June 15, 1954 [June 15, 1953], No. 17609/54. Class 106 (1). [Also in Group XL (b)] In apparatus for determining the value of a function of two -independent variables including a member with first, second and third tracks having code representations of the first and second variables and the function respectively, the code representations on the first track are sensed to determine the code value corresponding to the instantaneous value of one independently variable quantity, and, in response to this determination, the code value from the second track corresponding to another independently variable quantity is similarly determined, code values from the third track being indicated concurrently with the last-mentioned determination. In the apparatus shown, an endless transparent belt 20, driven at constant speed in direction 25 has four columns C<SP>1</SP>-C<SP>4</SP> of opaque marks sensed by photo-cells 34-37 respectively which receive light through a slit 32 from a source 30. The marks in columns C<SP>1</SP>-C<SP>3</SP> represent increments in the values of variables x, y and a function f(x, y) respectively, groups 27, 28 of marks, representing y, f(x, y), occurring for each x-mark 26 (see Fig. 2). In operation, a synchronizing mark 29 in column C<SP>4</SP> causes photo-cell 37 to send an actuating pulse to generator 44 which then applies a series of gating pulses to electronic switch 38 to allow pulses from 34 corresponding to marks 26 to be passed to counter or integrator 39 whose output voltage on lines 40 corresponds to the number of pulses supplied. When this voltage is substantially equal to a voltage, representing an instantaneous value of x, at terminals 42; comparator 41 resets integrator 39 through circuit 43, turns off generator 44, and turns on generator 51 which similarly controls switches 45 and 52 to allow pulses from 35 and 36 to be passed to integrators 46 and 53 respectively. When the output voltage from 46 is substantially equal to a voltage, representing y, at terminals 49, comparator 47 resets integrators 46, 53 through discharge circuit 50 and turns off generator 51. The output of integrator 53, representing the required value of the function, is applied to a peak-reading device 54, e.g. a recording voltmeter; this device may be reset to a reference potential by circuit 43 in response to comparator 41 during the next cycle of belt 20. The marks may be replaced by transparent portions or punched openings in an opaque belt, or by magnetic marks sensed by pick-up heads in place of photo-cells. The mark 29 may be interspersed with marks 26 and may be of electrically conductive form to complete a circuit between contact brushes. A reference column of marks or indicia may be provided to effect compensation for the speed of the belt, and a function of three variables may be accommodated. To accommodate functions which may increase or decrease as y increases, two columns on the belt may be used for the function values (Fig. 4, not shown). Reference is made also to the use of a binary code and to the replacement of the belt by a rotatable disc. Each comparator (Fig. 3, not shown) comprises a diode-resistance network which, when the compared voltages become equal, causes a one-shot multi-vibrator to be triggered through a differentiating circuit.