Patent GB-748306-A (GB)
Title: Integrating device
IPC: H03M1/00
Filed: 1953-09-25
Abstract: 748,306. Frequency measurements. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 25, 1953 [Sept. 30, 1952], No. 26444/53. Class 37. [Also in Group XXXVIII] An electronic device for integrating a variable given in analogue form and displaying the result in digital form comprises a pair of oscillators, the frequency of one oscillator being varied in accordance with the magnitude of the variable and the number of oscillations thereof occurring in one cycle of the second timing oscillator being counted, the frequency of the second oscillator and therefore the time of integration being also variable. As shown, Fig. 1, the frequency of a multi-vibrator-oscillator 2 is varied, e.g. by adjustment of the bias tapping 1 or by the adjustment of a capacitor C or a resistor in accordance with the instantaneous value of a variable, e.g. temperature. The oscillator output pulses are phase inverted at 42 and passed by a gating pentode 3, during each integrating interval, over line 43 to a digital counter, Fig. 2. The second timing oscillator, a free-running multivibrator 4, comprises triodes 14, 15 the repetition frequency of which is variable by means of a coarse potentiometer control 17 which adjusts the impedance of a tube 16 connected in series with resistors 18, 19 across the supply to vary the bias on tubes 14, 15, and a fine control 18, 19. In addition, a further manually set control 5 operates through tubes 21-23 to adjust differentially the respective conducting times of the triodes 14, 15 without affecting the repetition frequency. Operation. Closure of start contacts 9 switches a bi-stable trigger circuit 6 to the " on " position in which triode 7 conducts and triode 8 is blocked. The trigger 6, as it is switched on, pulses the tube 15 of the timing oscillator 4 so that tube 15 conducts and blocks 14. When tube 14 again conducts-after the normal relaxation time of the oscillator-it negatively pulses over line 33 a phase inverter 34 which positively pulses a further inverter 35, which over lines 37, 31 pulses the trigger circuit 6 to " off ", in which triode 7 is blocked and 8 conducts. As trigger 6 goes " off " it pulses over line 38 a similar trigger circuit 41 to " on " in which triode 40 conducts and 39 is blocked. While the trigger 41 is " on " it biases the gate valve 3 to " open ", and, as above described, passes pulses from the oscillator 2 to the counter during the time that tube 14 of the timing oscillator 4 conducts. When 14 ceases to conduct, it positively pulses line 33 and through phase inverter 34 negatively pulses over line 44 the grid of tube 40 to switch the trigger 41 to "off" and hence block the gate valve 3. The count is thus proportional to the repetition frequency of oscillator 2 and to the conduction time of tube 14 of oscillator 4. Electronic counter, Fig. 2. A decimal counter is used, each denominational stage, units, tens ... &c. being similar and comprising four trigger stages, 45, 46, 47, 48 corresponding respectively to the binary powers 1, 2, 4, 8. In the zero position of each stage all triggers are " off " in which case the left-hand tubes thereof conduct. All incoming pulses over line 43 actuate the units stage trigger 45, the following triggers 46-48 being operated according to the binary system for the first nine pulses. At the tenth pulse, all triggers in the stage are zeroized and a transfer pulse sent to the next higher denomination. The condition of each stage is indicated by neon lamps 75 which glow when the associated trigger is on. Resetting. Closure of reset contacts 86, Fig. 1, renders a tube 84 more conductive, the resulting positive impulse on a resistor 83 raising the anode potential of diodes D6, D41, D45 ... D48 to switch " off " the associated triggers 6, 41, 45 ... 48 thus zeroizing the counter and resetting triggers 6, 41.