Patent GB-720480-A (GB)
Title: Improvements in or relating to apparatus and method for recording variables
Inventor: MADSEN ROYAL GLEN
IPC: G05B19/42
Filed: 1951-11-16
Abstract: 720,480. Electric indicating systems. BECKMAN INSTRUMENTS, Inc. Nov. 16, 1951, No. 26906/51. Class 40 (1) [Also in Group XL(b)] A variable is recorded by causing it to vary the phase of a cyclical signal which is recorded simultaneously with a cyclical reference signal. During reproduction, comparison of the phase of these two signals enables the original variable to be reproduced. Recording. Fig. 1. The variable is converted by known means into the rotation of a shaft 30 which then positions the rotor of a selsyn 24. The stator windings of the selsyn are fed from a master oscillator 20, the output of which is split by a phase splitter 21 into two signals 90 degrees out of phase with each other but which may be any suitable phase angle apart. Thus the rotor of the selsyn has generated in it a signal, the phase of which with respect to the reference depends on the rotor position and which is used to modulate the output of an oscillator 34. The output of the master oscillator also modulates the output of an oscillator 35 and the signal from oscillators 34 and 35 are fed to a mixer 36 and finally recorded at 40 by known means such as cutting a continuous groove marking a photc sensitive film and recording magnetically. Reproduction. Fig. 2. The recorder 40 is now employed as a reproducer 40(a) and an output derived from it consisting of the signals corresponding to the outputs of the two oscillators 34, 35 are modulated one by the oscillations of the master oscillator and the other by the output of the selsyn rotor. The oscillations of the master oscillator are separated by a filter and demodulator circuit 42, and split into two components 90 degrees apart by a phase splitter 21a. The two components are then amplified by amplifier 22a, 23a and one component is fed to each stator winding of the selsyn 24a. The signal produced during recording by the selsyn rotor is separated by a filter and demodulator 43 and phase compared in a discriminator circuit 45 with the output induced in the rotor 29. Signals due to phase differences are amplified and used to drive a servo motor 47 to reposition the selsyn rotor and balance the discriminator. Thus the positions of the selsyn rotor during recording are reproduced. Circuits are described with reference to Figs. 3 and 4 (not .shown), in which the variables are recorded on a single recording strip. During recording, a single rotor oscillator feeds the stators of two separate selsyns; different oscillators being modulated by the selsyn rotor output. During reproduction, the signals of the master oscillator and selsyn rotor are separated by three filters, each rotor signal being thus compared with the reference oscillation in a different phase discriminator. Copying-milling machine. Fig. 5. In this application of the invention, an operator either sets an original pattern or follows a previously made pattern with a follower 109 by adjusting a pair of lead screws 103, 105 in the two co-ordinate directions. Geared to these lead screws are the rotors of selsyns 52 and 53 and the movements of the two screws are recorded by the method described above. The apparatus shown in the figure both records and reproduces. With the switches in the position shown, the output of the selsyn rotors are fed to modulators 70, 71 which modulate the output of oscillators 73, 74, the oscillation being fed through filters 78, 79 to a mixer circuit where they are mixed with the output of an oscillator 75 modulated .by the master oscillator 50 and recorded at 81. As in the previous arrangements, the stators of the selsyns are fed with the phase-split and amplified output of the master oscillator. During reproduction, the follower 109 is replaced by a milling cutter and switches 113 and 118 are changed over and servo motors 90, 91 clutched into engagement with the lead screws. The three recorded signals are separated by filters 78, 79, 80 and demodulated by demodulators and amplifiers 82, 83, 84. The reference signal is fed to phase splitter 51 and then to the selsyn stator windings, while the two other recorded signals are fed each to one of the phase splitters 87, 86 where they are phase compared with the signals from the selsyn rotors, the unbalance signal being amplified and used to drive the lead screws 103, 105 and reposition the selsyn rotors. Absolute positioning system. Figs. 6 and 7 (not shown). To ensure that the lead screw always starts at the correct place and not an integral number of revolutions of the selsyn rotor away, a number of selsyn rotors may be provided each geared to the preceding one so that the last will never move more than 180 degrees from its initial position. Each rotor modulates a different oscillator and all the signals are recorded. During reproduction, each selsyn is positioned in turn by a switch mechanism which compares a signal derived from the recorder with that from the appropriate selsyn which is then driven to a balance position. The switch then moves to balance the next fixed selsyn and so on. Recording spectrophotometer. Fig. 15. Radiation from a Nernst lamp 603 is monitored by a photo-cell 608 to maintain illumination intensity constant and is reflected by a condensing mirror 609 through a motor-driven chopper plate 610 and is then collimated by a lens 612 through a liquid cell region 613. The rays then pass through a gas cell region 616 and are focused by a lens 617 through an entrance slit 615 on to the face of a dispersing prism 618 by way of a condensing mirror 625. The displaced radiation is reflected on to the rear face of the prism by a mirror 626, re-dispersed and reflected again by a mirror 627 through an adjustable intermediate aperture 647 and is then reflected on to a second prism 630 As in the case of the other prism, the beam is re-dispersed and so passes finally through an exit .slit 632 to be directed by a mirror 634 on to a thermocouple 635, or, if a mirror 645 is in its lower position, one of the photo-multipliers 643, 644. The exit and entrance slits are adjustable by a motor 658 and the wavelength is selected by a motor 660 which rocks the linked prisms.  Record control system for recording spectrophotometer. Fig. 10. Since the intensity of the Nernst lamp is not the same at all wavelengths, the spectrometer may utilize the operating and reproducing arrangement described above for compensating for this. With no sample or a standard substance in place, the width of the exit and entrance slit is adjusted to maintain the output of the thermocouple or photo-cell constant as the prisms are rocked to their full extent, the relative positions of the prism and slit being recorded. These positions are then reproduced with a test substance in position and the output of the thermocouple indicates 'transmissivity directly. The apparatus is shown arranged for making the preliminary recording run. The prism rocking motor 206 adjusts the rotor of selsyn 52 while the slit width varying motor 215 adjusts selsyn rotor 53. The positions of these two motors are recorded at 81 by the arrangement already described. A D.C. generator 207 feeds a rate voltage to the servo amplifier .205 which feeds the wavelength motor while the slit motor adjusts a tap of a potentiometer 203 in this amplifier circuit to adjust the speed gf the wavelength motor in accordance with slit width. The output of the' detector 176 is maintained constant by applying its output through a synchronous rectifier to a differential amplifier where it is compared with the voltage set on a potentiometer 213, the difference being used to reposition the slit motor. At the same time the output of the detector is used to mark a recording drum which thus bears a line parallel to one axis. On the setting of the potentiometer depends the position of the line. So that the movement of the chart shall be in accordance with wavelength rather than slit position, the prism motor 206 instead of driving the drum directly adjusts the tap of a potentiometer 224, another tap on which is positioned by a servo motor responsive to the difference in potential between the two taps. The potentiometer is so constructed that the servomotor movement, which is transmitted through selsyn receiver and transmitter to the chart, is proportional to the wavelength passed by the prism. A system is described, Fig. 12 (not shown), in which recording and reproducing are effected by means of the same process and apparatus in the manner of Fig. 5. Recording a number of variables in order. Figs. 13 and 14 (not shown). In recording one of a number of variables at a time, each is arranged to position a selsyn rotor, but a master selsyn connected to a switch connects a particular one to the modulator. At the same time the position of the master selsyn and therefore of the switch is recorded. During reproduction, the rotor of the master selsyn connects each appropriate one of the other selsyns to the reproducer so as to reproduce its position during recording. An electronic arrangement is described in which a variable phase oscillator is fed with a voltage proportional to the signal to be recorded, its output being used to modulate a further oscillator. This signal is recorded along with the output of a further oscillator modulated by a reference oscillator and the frequency of the variable phase oscillator. A phase discriminator compares the outputs of variable phase and reference oscillators and provides a feed back signal to linearize the output of the variable phase oscillator. The two recorded signals are separated by filters and demodulated and compared in a phase discriminator which gives an output representing the original variable.