Patent GB-953522-A (GB)
Title: Alternating signal translating circuit
Inventor: YOUNG FRINK MANSFIELD
IPC: G01R19/00
Filed: 1962-12-27
Abstract: 953,522. Changing waveforms. ADAGE Inc. Dec. 27, 1962, No. 48723/62. Heading H2F. [Also in Divisions G1 and H3] Apparatus for translating and measuring an A.C. voltage source comprises a storage means adapted to acquire and release electrical energy, a first switching device for applying source signals to the storage during alternate half cycles and permitting current flow into and out of the storage, an impedance between the source and the storage, a second switching means connecting the storage to a direct current measuring device during the remaining half-cycles, and a return path connecting the source, the storage means, and the measuring device to a common reference potential. An A.C. source 11 to be measured (Fig. 1) is connected over mechanical switch 12 resistor 13 to capacitor 14 also connected over mechanical switch 16 to a high impedance D.C. measuring instrument 15. The switches are operated in opposite serges by electronic circuit 17 in synchronism with the source 11 (Fig. 2a) and the voltage at switch 12 comprises alternate sinusoidal half cycles and rectangular pulses (Fig. 2b) so that the voltage across the capacitor varies (Fig. 2c) with discharge from 0 to t 1  charge from t 1  to t 2  and discharge from t 2  to t 3  after which zero charge or discharge holds the voltage constant until the commencement of the next cycle. It is shown that the steady capacitor voltage is approximately equal to 2e/# where e is the source   peak amplitude so that the D.C. instrument reads proportion ately to the source voltage. In a modification (Fig. 3) the source 11 is connected over attentuating resistors 21, 22 to amplifier 23 shunted by capacitor 27 with feedback resistor 28 between the output and the junction of 21, 22; also connected to earth over switch 24. The output is connected over switch 26 to measuring device 15 returned to earth, and the switches are operated in phase synchronously with the source A.C. During open half cycles of switch 24 the capacitor is charged by corresponding half waves and on closed half cycles of switch 24, the input is by-passed and the capacitor allowed to discharge while the measuring device 15 is connected thereto by switch 26. The switches may be electronic. Two such circuits may be alternately connected to the measuring device. In a further modification (Fig. 4), the source 11 is connected over resistor 43 to the input of amplifier 23 with feedback over diode 38 and also over resistor 36 in series with oppositely poled diode 37. The base/collector circuit of transistor 31, is connected across diode 37 and the emitter is connected over resistor 39 to capacitor 41, also connected over synchronous switch 42 operated by device 17 to measuring device 15. On alternate half cycles diode 38 conducts to provide a low impedance feedback, thus reverse biasing the transistor to disconnect the capacitor from the A.C. source, while switch 42 connects the capacitor to the measuring device 15. On the remaining half cycles the feedback path over diode 38 is disabled and that over resistor 36 and diode 37 is operative to turn on the transistor and allow the capacitor to charge, while switch 42 is open.