Patent GB-666632-A (GB)
Title: Improvements in or relating to the amplification of minute space currents and to photo-electric cells
IPC: H03F3/40
Filed: 1948-02-28
Abstract: 666,632. Photo-electric cells. KALMUS, H. P. Feb. 28, 1948 [Jan. 6, 1944], No. 6279/48. Class 39 (i). [Also in Group XL (b)] The output of a photo-emissive cell 3 used for the measurement of light intensity is made intermittent for ease of amplification by modulating the electron stream by means of an A.C. fed magnet 6. The pulsating voltage developed across resistor 4 is fed through a condenser 7 to an A.C. amplifier 8 and then through a filter circuit 9 responsive to twice the magnet excitation frequency to an indicating instrument 10. A control voltage may be taken from terminals 12. In the Specification as open to inspection under Sect. 91 many arrangements using a magnetically modulated electron or ion flow were described including arrangements for rectifying the output of an amplifier of the above type by means of a vibrating contact operated in synchronism with the modulating field, or a pair of diodes in which the electron flow is suppressed by magnets operated in synchronism with the modulating magnets referred to above. These arrangements form the subject-matter of Specification 666,678. Induction of amplifier output.-Instead of rectifying the amplifier output it may supply the field of an instrument, the rotor of which is fed from the modulating magnet supply (Fig. 20, Cancelled, not shown). A number of photocells, Fig. 21 (Cancelled, not shown), the electron streams of all of which are modulated at the same frequency may be connected in parallel to supply the amplifier so that the output indicates the sum of their excitations. The photo-cell may be modulated at different frequencies, Fig. 22 (Cancelled, not shown), in which case a number of meters connected to the output may be so arranged that each responds to the input of a particular cell. A system is also described, Fig. 23 (Cancelled, not shown), in which the output of the amplifier is fed back to the magnet to modulate the photo-cell current. This is said to cause continuous oscillations at a definite frequency. In an extension of this system, Fig. 24 (Cancelled, not shown), a number of electromagnets each modulating the electron stream in a different device are tuned to different frequencies so that the system oscillates at a different frequency depending on which of the devices is carrying current. A number of similarly tuned meters in the output circuit indicates which of the devices is energized. Ratio indicating system, Fig. 25 (Cancelled).- Magnets 42, 43 are energized out-of-phase and resistors 53, 54 adjusted so that balance is indicated on meter 10. Increase of space current will cause the meter to be deflected in one direction or the other. In the system of Fig. 26 (not shown), the output is fed back to energize the magnets and the system is said to oscillate at one of two frequencies depending on which of the two devices has the greater space current. A pair of meters in the output circuit, each sensitive to one of these two frequencies indicates the degree and direction of the unbalance. Radiation measuring.-In the embodiment of Fig. 12 (Cancelled, not shown), electrons radiated from a disc-shape cathode pass to the inner walls of a tubular anode when an electromagnet supplying an axial field is de-energized. Energization of the magnet " focuses " the beam so that it passes through the anode and falls on a further tubular " collector " electrode situated at a greater distance from the cathode. Fig. 13 (Cancelled) shows the use of such an arrangement for the measurement of electromagnetic radiation indicated by the arrow and the reference L. The cathode 2 is mounted inside the vessel 1 which is permeable to the radiations and when radiation impinges on it a stream of electrons passes to an anode 3 or a collector 19 according to the instantaneous values of the magnet energization. The cathode.may be so shaped as to obey Lambert's cosine law. Gas pressure measurement, Fig. 3 (Cancelled).- Tube 13 connects with the pressure source to be measured. Magnet 6 modulating the ionic space current between electrodes 2, 3 is fed with an alternating current supply from a transformer 15. The alternating voltage developed across resistor 4 is fed through a condenser to an amplifier tuned to the magnet supply frequency. Arrangements for producing a harmonic frequency or square-wave output.-In the arrangement of Fig. 4 (Cancelled, not shown), a coil surrounding the valve deflects the electron beam on to or away from a collector electrode, each alternate half-cycle, the output of the device being a square waveform of the magnet supply frequency. In the arrangement of Fig. 6 (Cancelled), switching in of the battery 14 gives an output at the supply frequency while switching out enables the second harmonic to be taken from across resistor 4. The magnet coils may be mounted inside the vacuum tube as in Fig. 8 (Cancelled, not shown), with a consequent reduction in size and field strength. In this Figure also the cathode is extended to shield the anode from capacitative interference. In Fig. 11 (Cancelled, not shown), a number of anodes are provided, alternate ones being connected together. The output frequency may be made any desired harmonic of the input merely by increasing the number of such anodes. A simpler embodiment, Fig. 10 (Cancelled, not shown), has only three anodes, the outer pair being connected together. The voltages developed across these two outer and the central anode may be applied to a push-pull amplifier. This subject-matter does not appear in the Specification as accepted.