| 摘要 |
<p>1,116,905. Transmission over power circuits. BORG-WARNER CORPORATION. 7 Sept., 1965 [8 Oct., 1964], No. 38207/65. Heading H4R. [Also in Division G1] D.C. signals representing fluid pressure at the bottom of a deep bore-hole are transmitted to the surface using the earth as one conductor and a three-phase A.C. power line as the other via artificial star points. At the surface, a transformer 67, rectifier 71 and Zener diodes 85, 86 provide a stabilized D.C. voltage across a potentiometer 84, the negative end of which is earthed whilst the slider is connected in a series circuit comprising a recording instrument (not shown) connected to lines 95, 93, a milliammeter 63, and a resistor 56 which may be varied in accordance with the length of power cable in use, to the star point 40 of three inductors connected to the power cable 14. At the downhole end of the cable, the circuit is completed to earth from a similar star point 20 through a resistor 35 which is varied in accordance with fluid pressure. Changes in pressure are thus directly indicated on the meter 63. Signal components of supply frequency are eliminated by tuned circuits 50, 51 and 30, 31, and by filter capacitors 52, 53 and 32, 33. To calibrate the meter 63 it can be connected by switch 57 directly through a standard resistor 61, to earth whilst the supply voltage is adjusted by potential divider 84. The signalling circuit is also used to operate an alarm if the motor of a pump situated down the bore-hole over-heats, thereby opening a thermal switch 37 and interrupting the D.C. circuit. The meter 63 then falls back to zero closing internal contacts (not shown) which energize an alarm relay 74.</p> |
