Patent GB-920062-A (GB)
Title: Improvements relating to apparatus for recording process information
Inventor: HARTLEY KENNETH ALISON
IPC: G01D15/20
Filed: 1958-03-25
Abstract: 920,062. Electric selective signalling. COURTAULDS Ltd. March 24, 1959 [March 25, 1958; July 15, 1958; Oct. 9, 1958], Nos. 9498/58, 22596/58 and 32216/58. Class 40 (1). [Also in Group XXXVI] Apparatus recording process information comprises transducer means responsive to the variable to be recorded to generate a voltage output proportional to the instantaneous value thereof, a device for producing a signal of increasing voltage for comparison with the output, and a detector responsive to equality between the output and signal voltages, thereupon to arrest the increase of signal voltage and to operate a switching mechanism to a setting determined by the signal voltage magnitude, so as to control an electromagnetic typewriter to record a number proportional to the signal voltage and thus to the transducer output. In Fig. 1 voltages derived from plural transducers 5 sensitive to, e.g., temperature, pressure, or flow rate are selected by switch 1 operated by motor 2 to connect directly or through relays (not shown) the successive voltages to self-balancing potentiometer 8 energized by a standard voltage source; for comparison with an increasing voltage from the potentiometer until null, at which the voltage increase is arrested. The potentiometer is geared to rotate the slider of a multiple (e.g. 100) contact digital switch 12 of which each contact represents a step of the input value to be measured and is connected to a corresponding contact on bank A of an 8-bank stepping switch 17. On selection of a particular digit switch contact all the moving contacts 18 of the stepping switch automatically and simultaneously move to a corresponding position and are arrested therein by operation of a relay (not shown) through the digit switch. The contacts of bank B are connected in two groups of 10 to the 0 to 9 unitary inputs of an electromagnetic typewriter (not shown) while those of bank C are commoned in two groups of 10 and connected to the " 0 " and " 1 " decimal inputs so that the typewriter will print values from 0 to 19 according to the positions of the switches 12 and 17. Contacts of column D are alternately connected to the " 0 " and " 5 " unitary inputs and those of column E are connected in sequential pairs to the decimal inputs from 0 to 9, enabling values to be printed from 0 to 95 in increments of 5. Contacts of column F are connected to unitary inputs with successive increments of 3 while those of column G are connected in commoned groups of 3 to successive decimal inputs from 0 to 9 enabling values to be printed from 0 to 57 in increments of 3. Switch 1 has addittional contacts (not shown) selecting the control contacts appropriate to each transducer. Contacts of bank H are connected to corresponding bus-bars 19 brought out to ranges of terminals 20, 21 of which each pair corresponds to a transducer; the bottom terminal of each pair being selectively connected to the bus-bar representing the minimum allowable value for the variable to which the particular transducer is reponsive and the top terminal being selectively connected to the bus-bar representing its maximum value. The pairs of terminals are scanned in sequency by a switch (not shown) ganged to the transducer selector switch 1 so that at maximum or minimum value, contact 18 completes a circuit to sound an alarm, mark the record, or operate a control. The sequence of operations of the typewriter is controlled by a sequence switch (not shown) relay operated in synchronism with selector switch 1 and connects the typewriter in turn to the appropriate banks of the stepping switch, zeroizes the stepping switch after each reading, and restarts the system on completion of a cycle of operation. In the self balancing potentiometer circuit (Fig. 2) the voltage signal from a selected transducer 22 is compared in an oscillatory chopper switch 23 with a voltage derived through potential divider 30, 31 from contact 24 scanning over fixed taps of a resistance chain 27; the chopped error voltage being fed to a phase sense comparator 28 fed from the oscillator to develop a pulse at null operative to arrest contact 24 at the appropriate point and to operate the recording apparatus as above. Alternatively in Fig. 3 (not shown), an input transducer voltage is compared in a resistance addition circuit with a digital ramp voltage derived from a stepping multiple cathode selector tube, and the error signal is chopped by an intermittently short circuiting transistor circuit pulsed from the selector tube to operate a phase sense detector to produce a pulse at null which arrests the operation of the selector tube; the value of the ramp voltage being then applied to operate the recording apparatus.