Patent GB-826341-A (GB)
Title: Improvements in or relating to integrators and automatic controllers
Inventor: STEGHART FRITZ LUDWIG FELIX
IPC: G05B11/01
Filed: 1954-10-18
Abstract: 826,341. Analogue computers. TINSLEY INDUSTRIAL INSTRUMENTS Ltd., and STEGHART, F. L. F. Jan. 16, 1956 [Oct. 18, 1954; Oct. 29, 1954], Nos. 29990/54 and 32902/54. Class 37. [Also in Group XL (c)] In a circuit for integrating a bidirectionally varying D.C. voltage employing a resistorcapacitor network, the voltage appearing across the capacitor is fed to an amplifying circuit, the output of which is applied over a high insulation feed-back connection to the resistor-capacitor circuit to compensate the voltage developed across the capacitor. The amplifier may include a thermionic discharge tube and a saturable reactor, a transistor or a vibrator. In a controller providing integral and differential components as well as the signal to a load 58, Fig. 1 (the first Provisional Specification), the input 1 is opposed by a potential tapped off from potentiometer 11 fed from a stabilized source 7. A fraction of this resulting potential is applied to discharge tube 16 energized by supply 18 to develop an output across resistor 19. The standing D.C. is backed off by a connection over resistor 23 to the supply 7. The potential appearing across the resistor 19 is applied over resistor 25 to the integrating capacitor 24, the voltage across which is fed to the grid of amplifying tube 40. The variation in anode current of tube 40 flowing through the reactor winding 39 controls the D.C. potential appearing across resistors 36, 35, part of which a tapping 37 is applied in series with resistor 25 to off-set the voltage developed across capacitor 24. The voltage applied to the grid of tube 40 is augmented by a voltage proportional to the input signal developed across resistor 20 together with a first differential component obtained by the use of capacitor 43 and resistor 41. The output 58 may control an electrically-operated valve positioner of an air or oil pressure device. When starting up the apparatus the capacitor 24 may charge unduly and a large overswing may occur in the output. To avoid this biased rectifiers 33, 34 are switched into the integrating circuit initially so that the potential across capacitor 24 may not rise above the corresponding bias valves as set by potentiometers 29, 30. The switch 45 may be moved to the central position to give hand operation, the current through the control winding of reactor 39 then being adjusted by a variable resistor 47. This resistor is calibrated on the same scale as the ammeter 44 so that the resistor 47 is set to agree with ammeter 44 before changeover is made, the capacitor 24 being charged over resistor 52 from the potential appearing across resistors 35, 36. This is the voltage required to give an output similar to the current flowing through the control windings of the reactor from the hand control. The capacitor 24 is thus charged to a value such that on return to automatic operation there is a smooth transfer of control. In the third position of switch 45 the control is by means of resistor 47 and ammeter 44 and the apparatus may be removed for servicing. In a modification, Fig. 2 (not shown), the capacitor 24 is electrolytic and may be charged in one direction only. A capacitor is connected between the join of resistors 41, 54 and the cathode of tube 40 to reduce the effects of pick-up, as described in Specification 826,342. In a further modification, Fig. 1 (the second Provisional Specification), the proportional current is supplied directly from tube 16 to output 58 and tube 71 provides the integral and differential component. The potential appearing across capacitor 24 is applied to the grid of tube 71 which provides an output across resistor 79. This potential is applied to the grid circuit of tube 64, the anode current of which passes through resistors 61, 62 to develop a potential equal and opposite to that of capacitor 24. Resistors 55, 60 and 66 provide negative feed-back to the appropriate tubes.