GB1444617A - Logarithmic recording system - Google Patents

Abstract

1444617 Function generators T MATSUMOTO 12 Oct 1973 47825/73 Heading G4G [Also in Division G3] A logarithmic recording system having different recording ranges each corresponding to a digit in the value being recorded, comprises a range-switching amplification circuit 28, 11 the output of which is compared to the output of a logarithmic potentiometer 18 in a differential amplifier 13, the latter providing power for a motor which drives the common shaft of the recording pen, the log. pot. 18 and the range switches 11, 20. Resistances R 1 -R 7 arranged in the feedback path of amplifier 28 have increasing values such that each is 10 times the preceding one. They are connected to the segments 22c to 22i of a rotary switch 22 having wipers 22a, 22b angularly spaced to provide a makebefore-break action. The output e A of amplifier 28 is applied to terminal 13a of differential amplifier 13 and the output e B of log. pot. 18 is applied to the other terminal 13b. The output of amplifier 13 is converted to A.C. and used to drive a servomotor (not shown) having a shaft 19 common to the log. pot. and to a rotary switch 20. Wipers 20b, 20c of switch 20 are so arranged that, as the wiper 18b of the log. pot.1 8 moves across the gap between the extremities 18c, 18d of the logarithmic winding 18a, one of the wipers 20b, 20c moves out of contact with the single electrode 20a. Thus at the upper or lower end or a particular range, the switch 20 is actuated to energize one of the relay windings Y 1 , Y 2 and to de-energize the other. During the short space of time that both wipers make contact with the electrode 20a the system is balanced by contacts Y 1A , Y 2A and neither relay is operated. Relay contacts Y 1B , Y B2 are connected to the wipers 22a, 22b of range switch 11 and the range switch is driven from the servomotor shaft hrotgh a rueduction gear in such a manner that the wipers make contact with two adjacent segments as the relays are actuated. Thus, a smooth transition from one range to the next is achieved. For decreasing values of the input signal, the system operates according to a reversal of the above procedure. A modified log. pot. is described (Fig. 3, not shown) which consists of two series-connected semicircular windings each with a respective wiper, the wipers being so orientated that one wipes through 0 to 180 degrees before the other wipes through 180 to 360 degrees. The points corresponding to 0 and 360 degrees are connected to terminals T 11 , are connected by a conductor. The wipers are connected to the terminal T 10 through a twoway switch.