Patent GB-706749-A (GB)
Title: Improvements relating to the recording of transients
IPC: G01R13/06
Filed: 1952-05-15
Abstract: 706,749. Recording-apparatus. METROPOLITAN -VICKERS ELECTRICAL CO., Ltd. May 15, 1952 [May 23, 1951], No. 12314/52. Class 106 (4) A method of recording transient values of an electrical or other quantity consists in continuously recording on a moving endless surface magnetic representations of the instantaneous values of the quantity, automatically effecting, on the occurrence of a transient and at a position spaced in the direction of movement of the endless surface from the position at which recording is effected thereon, magnetic reproduction of the representations on a magnetizable tape to obtain on the tape a magnetic representation of the values of the quantity obtaining during and for some time before the transient and erasing the magnetic representations from the endless surface after they have passed the position at which reproduction on the tape is effected and before reaching the recording position. Apparatus is shown for recording transients occurring in a transmission line 4 and comprises a frequency modulation converter 1 inductively coupled to the line 4 by a current transformer 3 in closed circuit with the input terminals of the converter 1 and with a transient sensing electromagnetic relay 2. The converter 1 produces a constant amplitude, frequency modulated output signal indicative of the amplitude variation of the input signal and across the output terminals is connected a recording head 5 which magnetically records on the endless peripheral surface of a drum 6 of material having very high magnetic permeability, e.g. a composition of copper, nickel and iron known as cunife. An erasing head 7, e.g. a permanent magnet eliminates the recording just before the surface passes the recording head 5. After a record is made and before it is erased, it passes a tape 9 whose adjacent surface has high magnetic permeability. The tape 9 may be of steel or of plastic with an oxide covered surface, e.g. ferro-magnetic oxide, and it can be drawn from a supply reel 10 to a take-up roller 11 with idler roller 11a to prevent slipping passing over two idler rollers 8a. 8b mounted on a member 8 which can be raised by the action of a solenoid 12 to cause the tape 9 to contact and conform to the surface of drum 6 so that the record is reproduced on the tape 9. In operation, when a transient occurs in the line 4, the relay 2 is excited, latched and closes contacts 2a, the relay 16 is then excited, opens contacts 16b and closes contacts 16a so that relav 12 is excited. latched, brings the tape 9 into contact with the drum 6 and closes contacts 12a. A circuit is then closed through relay 25 to close contacts 25a and start a motor 19 which drives the tape 9 at the same sneed as the drum 6 and drives cams 20, 18 which, at intervals corresponding to the average duration of a transient. close contacts 21, 17, the second lagging a little behind the first The closed contacts 21 complete a circuit through relays 23. 22, the first causing clock mechanism 24 to time stamn the tape 9 and the second unlatching the relay 2 which will be relatched again as soon as the contacts 21 open unless the transient has ceased. Upon the first unlatching of the relay 2 after cessation of a transient the contacts 2a open. relav 16 is de-energized and onens contacts 16a to de-energize relav 12 and contacts 16b close so that when contacts 17 close in their turn relay 13 is excited and unlatches relav 12 to move the tane 9 out of recording position and to onen contacts 12a and stop the motor 19. The tane 9 may be fed through frequency lowering transcribing equipment which converts the frequency modulated signal to an amplitude modulated signal which may be applied to a direct-writing recorder to give a graph of the transient values. Besides current, voltage, power and other aspects of the transient may be recorded by arranging a plurality of recording heads side-by-side across the drum 6. A recording head may also be provided for recording the unmodulated carrier frequency of the converter to be used for correction purposes if errors due to slipping or variations of speed have been introduced.