| 摘要 |
1,010,674. Automatic control systems. PHILIPS ELECTRIC & ASSOCIATED INDUSTRIES Ltd. Dec. 24, 1963 [Dec. 27,1962 ], No. 50951/63. Heading G3R. [Also in Divisions G1 and H3] Circuit arrangement measuring and controlling the ratio between two impedances are connected in series with an A.C. source and with the output impedance of an amplifier, in such manner that negative feedback is provided across the amplifier; one of the impedances being connected in the amplifier input circuit and the voltage amplification of the amplifier being unity. In Fig. 1 an A.C. source energizes the primary of transformer 2 whose secondary is centre tapped to the input of amplifier 5 whose output energizes the primary of transformer 6. Resistors 3 and 4, whose ratio is to be determined, are series connected to change over switch 7 selecting the lower terminal or the centre tap of the secondary, and to the lower end of the secondary of transformer 6 whose upper end is connected to the upper end of the secondary of transformer 2; the function of the resistors being earthed. The voltage across the secondary of transformer 6 is arranged to be equal and opposite to the voltage at the amplifier input, and the amplifier may be a cathode follower or emitter follower. It is shown by mathematics that E 1 = 1 - R 1 /R 2 E 0 where E 1 is the voltage across the output transformer secondary, E 0 is that across the input transformer secondary and R 1 , R 2 are the values of resistors 3, 4. Also that E 1 = R 1 /R 2 E 0 with switch 7 in its upper position. The requisite voltage may be indicated directly by a measuring instrument or vacuum tube voltmeter, or may be employed to operate a control system, e.g. for an electrolytic process in which one of the resistance values depends on the conductivity of an electrolyte and the other is a reference value, which restores the resistance difference and the control voltage to zero. A procedure for compensating circuit errors is described. |
