Patent GB-884360-A (GB)
Title: Improvements in apparatus for indicating or/and recording or/and signalling in digital form measured values of variables
Inventor: WORSWICK BERNARD AUGUSTINE
IPC: H03M1/00
Filed: 1957-01-25
Abstract: 884,360. Potentiomotive voltage measuremerit. BAILEY METERS & CONTROLS Ltd. Jan. 22, 1958 [Jan. 25, 1957], No. 2752/57. Class 37. [Also in Groups XXIV and XXXVIII] Apparatus for indicating, recording, or signalling in digital form a measured e.m.f. representing a variable, wherein a plurality of digit indicating, recording, or signalling units correspond to the respective digital places of the number representing the measured value, and means are provided for furnishing for each unit an e.m.f. representing the digit set up therein and the digital place of such digit in the number to be indicated, recorded, or signalled; there being provided means for effecting the setting up of the appropriate digits by automatically operating the units successively in order from the unit appropriated to the highest digital place of the number to be indicated, recorded, or signalled to the unit appropriated to the lowest digital place in such number; in which the operation of each unit comprises the drive thereof from the state in which digit 0 is set up therein to the state in which digit 9 is set up therein, and termination of the drive in such state if a combined e.m.f. representing the sum of the e.m.f's. furnished by the said units is less than the e.m.f. representing the variable or differs from it by a small value, but otherwise comprises continuation of the drive in the sense corresponding to successive setting up of digits 9, 8, 7 . . . 1, 0 in the unit until termination of the drive when the said combined e.m.f. becomes less than the e.m.f. representing the variable or differs from it by a small value. In apparatus for indicating and/or recording in digital form a measured value of a variable in the form of a unidirectional voltage, a digit indicating and/or recording unit (Fig. 1) comprises a motor I driving over shaft 2 and a slipping clutch (Fig. 2, not shown), a spur wheel 3A carrying a 20-tooth ratchet wheel arrestible by a sprag 11A displaced by energization of electromagnet SPSA. Wheel 3A drives through a 1 : 2 step-down a digital decade type wheel 13A printing through ribbon 16 on paper 15 when platen 14 is electromagnetically lifted on energization of relay PT; and also a gear-wheel 17A rotating the wiper of 10-position rotary switch 22A having contacts 22A-0 to 22A-9 connected to respective tapping points 23A-0 to 23A-9 of a linear constantly energized resistance potentiometer so as to develop at the wiper a voltage proportional to the operative type wheel digit. Diametrically opposed pins of the spur wheel close normally open contacts AZC1 at zero position. Two further digital units having spur wheels 3B, 3C are driven by motor 2 and may be retained in printing position by operation of sprag electromagnets SPSB, SPSC. Platens, ribbons, type wheels and recording paper are provided as above, with corresponding rotary switches, resistance potentiometers, and constant sources of energization whereby first, second and third digits of a decade measurement reading may be recorded and the respective voltages A, B, C may be combined at 41 (Fig. 3), to represent the total printed reading, with an additional voltage representing half a unit of indication, and the total compared at 42 with a voltage X representing an unknown variable, which may be derived from a motor-driven switch 121 selecting from plural voltages; thedifference voltage operating electromagnets SPSA, SPSB, SPSC so that the spur wheels are arrested successively in respective positions such that the total of voltages A, B, C balances or approximately balances the voltage X to produce a null value, at which the value of X is registered in the order of the 100 digit, 10 digit and unit digit. The difference voltage from each unit is chopped for A.C. amplification by normallyclosed relay contacts CH1 shunted across the output of 42 and opened by relay CH excited by a trigger circuit 47 in response to a phototransistor 46 whenever a beam of light shines thereupon from lamp 44 through aligned apertures 43, of which twenty are uniformly disposed on each spur wheel. When contacts CH1 are open the output from 42 is amplified at 48, 49, differentiated at 50, gated at 51 which opens in response to trigger 47 when the phototransistor is darkened and closes when it is illuminated, and is amplified at 52 to energize thyratron or cold cathode gas-tube relay 53. As the wiper of rotary switch 22A moves over its contacts, the output of 42 decreases stepwise (Fig. 4a) to a sign reversed final value, and the apertures 43 are aligned or misaligned for light transmission as shown (Fig. 4b), so that contact CH1 is alternately opened and closed to modulate the output of 42 into isolated square waves (Fig. 4c) differentiated at 50 (Fig. 4d), from which alternate pulses are removed by gate 51 (Figs. 4e, 4f), so that phaseinverting amplifier 52 yields a train of diminishing negative pulses followed by a positive pulse corresponding to the final step (Fig. 4a), which fires relay tube 53 to operate relay CO through contacts DC4 of relay DC (Fig. 5) in series with normally closed contacts PT2 of relay PT and normally closed contacts ZR5 of relay ZR. In Fig. 5, a relay DC operates simultaneously contacts DC4 and switches DC1, DC2, DC3, which have four positions assumed on successive excitations. DC2 in its first position closes contact II, III, IV and opens contact I; in its second position it closes contacts I, III, IV and opens contacts II, and operates similarly in its remaining position. Switches DC1, DC3 in their four successive positions select corresponding contacts I to IV. Electromagnet SPSA is energizable through relay contacts ZR1 in normal position, and switch DC2 in positions II, III or IV, or when DC2 is in position I, through closed contacts C01 of energized relay CO ; switch DC1 being inserted between contacts C01 and ZR1. Similarly, electromagnet SPSB is energizable through contacts ZR2 in normal position and switch DC2 in positions I, III or IV, or when DC2 is in position II through closed CO1 contacts and switch DC1 and electromagnet SPSC is energizable through contacts ZR3 in normal position, and switch DC2 in positions I, II, IV, or when DC2 is in position III through closed CO1 contacts and switch DC1. On operation of relay ZR electromagnets SPSA, SPSB, SPSC can only be energized over normally open zero contacts AZC1, BZC1 and CZC1 of the respective digital units with a certain time delay over switch DC3 in position IV, and before operation of contacts ZR4, relay PT is energized to operate the printing electromagnet. Relay DC is energizable over control contacts CC1 and ZR4 when operated, and switch DC3 in position IV; and is also energizable over contacts CO in operated position. In operation with the type wheels and rotary switch wiper arms of the three units standing at zero and switches DC1, DC2, DC3 at position IV, relay ZR is energized and electromagnets SPSA, SPSB, SPSC operate to arrest their respective ratchets. Manual or automatic closure of control contacts CC1 operates relay DC to step switches DC1, DC2, DC3 from position IV to I. ZR releases, and electromagnets SPSB, SPSC are energized over contacts ZR2, ZR3 and switch DC2 to arrest ratchet wheels 3B, 3C while electromagnet SPSA is inoperative since DC1 and CO1 are open, so that wheel 3A of the 100's recording unit rotates with the wiper arm of switch 22A to interrupt the light beam to phototransistor 46 so that contacts CH1 chop the output of 42. While the voltage on the wiper arm 22A exceeds that representing the measured variable, tube 53 receives a negative pulse and does not fire, relay CO is inoperative, contacts CO1 remain open and the wiper arm moves to the next lower one of its range of contacts successively until tube 53 receives a positive pulse and fires, relay CO operates, contacts CO1 close, electromagnet SPSA is energized, and the 100's recording unit is arrested at the appropriate digit. A circuit completed through CO1 and relay DC steps switches DC1, DC2, DC3 from position I to II while contacts DC4 open at each step to de-energize tube 53 and relay CO to open contacts CO1. Electromagnet SPSA remains energized over contacts ZR1 and switch DC2, while electromagnet SPSC is energized over contacts ZR3 and DC2, but electromagnet SPSB is de-energized so that wheel 3B rotates until its associated wiper arm derives a voltage such that tube 53 receives a positive pulse and fires; relay CO operates, closes contacts CO1, and operates relay DC to step switches DC1, DC2, DC3 from position II to III. Contacts DC4 open, de-energize tube 53, and release relay CO to open contacts CO1 so that the 10's recording unit is arrested at the appropriate digit. Similarly, the units recording unit is set up by rotation of wheel 3C, and relay CO is operated for the third time to close contacts CO1 and operate relay DC to step switches DC1, DC2, DC3 from position III to IV. Switch DC3 energizes relay PT to print off the three-digit number representing the input which is set up on the type wheels, and also energizes relay ZR to open contacts ZR4 and after delay to release relay PT to disengage the paper from the wheels; tube 53 being meanwhile disabled over contacts PT2 and ZR5. Contacts ZR1,ZR2,ZR3 also operate to open the circuits of electromagnets SPSA, SPSB, SPSC until the respective zero contacts AZC1, BZC1 or CZC1 close, and the type wheels are thus rotated into their zero position in preparation for a further operation on closure of contacts CC1, which are operable by hand when required, or by cyclic mechanism to indicate successive periodic voltage values of a single variable, or periodic instantaneous voltage values of plural variables from selector switch 121 driven (Figs. 3, 6) by a motor 122 over contacts 123 on which plural input voltages are imposed. Simultaneously driven duplicate switches 124, 125 respectively have adjacent contacts