Patent GB-422518-A (GB)
Title: Improvements in or relating to apparatus for testing the running of clocks, particularly those which are provided with a balance
IPC: G04D7/12
Filed: 1934-02-26
Abstract: 422,518. Testing clocks. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Feb. 26,1934, Nos. 6261 and 6262. Convention dates, Feb. 25, 1933 and June 3, 1933. [Class 139] In an arrangement for testing the running of clocks, particularly balance regulated clocks, the frequency of the balance, anchor, or other oscillating part of the clock is compared with a standard frequency (at which the balance should oscillate), the phase displacement between the two frequencies being indicated on a current measuring device fed with impulses the duration of which depend on the phase displacement. The current measuring device is actuated by two relays, for example, ionic tubes, the grids of which are fed respectively with voltage impulses, the frequencies of which correspond to those of the clock under test and the standard frequency. Various methods of obtaining these impulses are described. For example, the beats of the anchor or escape wheel may act through a microphone and an amplifier, or the clock may be secured on a resiliently mounted base, the natural frequency of which is made to equal that of the balance in which case the periodic movements of the base actuate an amplifier, for example, electromagnetically. Again the impulses may be produced by a photo-electric cell, the illumination of which is influenced by the balance &c. A method of rendering the ionic tubes susceptible to the voltage impulses pertaining to the ticks of the anchor only and not to other noises obtaining in the clock is also described. In Fig. 1, 1, 2 are the ionic tubes to the grids of which the voltage impulses 1a, 2a, Fig. 1a, pertaining to the clock under test and the standard frequency (standard clock) respectively, are applied. 8 indicates a constant voltage supply fed to the tube anodes through a relay 7 and resistances 5, 6. When an impulse 1a arrives, the tube 1 starts, the anode current thereof flowing through the current measuring instrument 4 and resistance 5, until an impulse 2a arrives and starts the tube 2 when the tube 1 is extinguished by a current impulse through a condenser 3. The next impulse 1a starts the tube 1 and through the condenser 3 extinguishes the tube 2 and so on. The tubes thus interact to extinguish each other, and, as the instrument 4 is in the anode circuit of tube 1, current passes therethrough only in series with the tube 1, that is, as shown in Fig. 1a, during the intervals between the arrival of the impulses la and 2a. From Fig. 1a it is seen that provided the instrument 4 is sufficiently damped, it will give a steady reading only if the phase displacement between the impulses 1a and 2a remains constant, that is if the frequency under test and the standard frequency are equal. The instrument reading is therefore an indication of the phase displacement and variations in the reading indicate whether the clock under test is going too fast or slow. The instrument 4 may have a mechanical restoring force, or an electrical restoring force may be used to render ineffective changes in the voltage supply 8. A limit relay 7 is provided to break the anode circuits to extinguish both tubes, should they both be started together by impulses 1a and 2a arriving simultaneously. Fig. 2 shows an oscillograph record of the voltage impulses corresponding to the ticks of a clock. It will be seen that numerous parasitic voltage impulses occur between the tick voltages, and to prevent these unwanted voltages influencing the ionic tubes the arrangement shown in Fig. 3 is used. The voltage impulses of the clock under test and a corresponding standard clock are applied to coils 10, 11 respectively, connected to amplifiers 12, 13. The amplifiers are non-linear so as to amplify the required tick voltages to a greater extent than the parasitic voltages, and include rectifiers, and oscillatory systems, electrical or mechanical, tuned to the standard frequency, further to reduce the parasitic voltages. The output coils 14, 15 energized by the oscillatory systems act on coils 16, 17 in the grid circuits of the ionic tubes 18, 19. The two tubes interact as described above by means of a condenser 29 and the measuring instrument 9 in the anode circuit of tube 18 functions similarly to 4 in Fig. 1. The two anode circuits, however, include transformers 23, 24, which, when the respective tubes start, charge condensers 21, 22, respectively, which take nearly the periodic time between successive tick voltage impulses to discharge through the rectifiers 25, 26 (in the blocking direction) or suitable discharge resistances, and thereby render ineffective the parasitic parts of the voltage curves between the tick voltages. A limit relay 30 is again provided. Instead of ionic controlling relays mechanical relays may be used.