Patent GB-600077-A (GB)
Title: Improved apparatus for the automatic adjustment of an electric circuit to produce a maximum effect
IPC: H03J3/00
Filed: 1945-04-19
Abstract: 600,077. Impedance measurements. BRITISH INSULATED CABLES, Ltd., QUAYLE, J. C., and JONES, P. April 19, 1945, No. 9876. [Class 37] [Also in Group XXXVIII] The invention relates to the automatic adjustment of an electric circuit to produce a desired maximum effect in which a circuit member is continuously adjustable through a range including the condition for that effect, and is applicable to the tuning of oscillatory circuits, automatic balancing of Wheatstone and similar networks, control and recording of pH values, temperature, thickness or other measurement that can be translated into electrical parameters and compared with a standard. During the initial sweep of the circuit member, the maximun responder of a device measuring the effect of the adjustment on the quantity under consideration is left in a position determined by the maximum effect and during the succeeding sweep the normal responder of the measuring device is actuated until it registers coincidence with the maximum responder when the circuit adjusting member is automatically stopped. As shown, for automatically tuning a circuit 1 to an incoming wave, the tuning condenser 2 is continuously adjustable by a uni-selector switch (not shown) which also drives switch arms 14, 27. Assuming that the condenser 2 is at the beginning of its range when the apparatus is switched on, the biassing voltage from source 26 together with the voltage from tapping 13 on the inductance 10 charges a condenser 21 through the rectifier 17. As the tuning condenser 2 is rotated, the charge on the condenser 21 builds up to a maximum corresponding to resonance of circuit 1, and this charge is retained by appropriate dimensioning of the time constant of the grid circuit of valve 7. The contact 14 moves to the contact 16 as the condenser 2 commences its second sweep, whereupon the potential on arm 14 is applied, through rectifier IS to charge a condenser 22. When this condenser is charged to the same voltage as condenser 21, that is when the circuit 1 is again in tune, the bridge 3, 4, 7, 8 is balanced and a relay 25, energized by the bridge output, de-energizes to stop the stepping switch and hence the condenser 2 in the resonance position. Auxiliary switching operations may be effected by additional banks of the stepping switch, e.g. (1) to operate an alarm in the absence of any H.F. output from the circuit 1 or where the circuit does not tune to resonance ; (2) to ensure that the switch always returns to the initial position if the bridge balance is disturbed. When the bridge is balanced and the stepping switch at rest, the condenser 22 remains charged from the circuit 1. The charge on condenser 21, however, gradually leaks away to unbalance the bridge. Unbalance also takes place if the conditions in circuit 1 change. Response of the stepping switch to these changes may be delayed or suppressed by arranging that the relay 25 can be re-energized only by a manuallyoperated switch. The tuning process may be repeated at intervals. In other applications, the circuit to be controlled may be introduced in the place of circuit 1 and the adjustable member may be a reactance or resistance dependent on the nature of the adjustment. The measuring device will respond to or indicate a circuit condition which may be any parameter expressible as a function of voltage or current. In the case of an A.C bridge, e.g. the setting may be indicated by a voltage condition adapted to be a maximum in the balanced condition.