Patent GB-754176-A (GB)
Title: Improvements in or relating to telemetering installations
IPC: G08C19/02
Filed: 1954-07-20
Abstract: 754,176. Electric telemetering systems. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. July 20, 1954 [July 30, 1953], No. 21168/54. Addition to 748,534. Class 40(1) The electromagnetic comparators of the telemetering system described in the parent Specification are replaced by magnetic amplifier type comparators. Transmitter comparator Fig. 1. This comprises identical magnetic circuits 104, 104<SP>1</SP> of which the coils 101, 101<SP>1</SP> carry the direct current I1 proportional to the variable to be transmitted and derived from a translator 1. The coils 102, 102<SP>1</SP> carry a D.C. proportional to the frequency difference F1-F2 of oscillators 2, 3 derived in the frequency measuring convertor 4a, and the coils 103, 103<SP>1</SP> carry a fixed D.C. The magnetic circuits are energized over a transformer 106 the rectifier bridges 105, 105<SP>1</SP>, the energizing current producing unidirectional opposed voltages across resistors 109,. 109<SP>1</SP> which are equal in the balanced condition of the comparator. When the current I, has zero value the frequency difference F1, F2=fo the basic frequency, in Which case the ampere turns of the coils 102, 102<SP>1</SP> cancel out; those of the coils 103, 103<SP>1</SP>, respectively. Any change in the value of I1 varies the potential drop across the resistor 33 to adjust the frequency of the oscillator F2 and hence the DC flow in the coils 102, 102<SP>1</SP>. If the frequency difference is proportional to I1 the ampere turns of the three windings 101, 102, 103 and 101<SP>1</SP>, 102<SP>1</SP>, 103<SP>1</SP> cancel one another respectively, but should this poroprtionality be departed from, the reactances of the magnetic circuits 104, 104<SP>1</SP> vary differentially to produce a resultant D.C. voltage across the points 111, 112, which after filtering at 113, 114 produces a voltage drop across the resistor 34 to adjust the frequency F2 until proportionality is restored. The two frequencies F1, F2 are transmitted to line 36. Frequency measuring converter Fig. 2. The frequencies F1, F2 are mixed at 151, the difference frequency being selected at 152, frequency multiplied by n at 153, and at 154 converted to rectangular wave form and differentiated, the resultant positive pulses 155 firing a thyratron 156 at the frequency n (F1-F2). The thyratron is fed from the D.C. source 21 in series with the coils 102, 102<SP>1</SP> and across its anode cathode is connected an oscillatory circuit 160-161 which is lowly damped and has a relatively sort time constant which results in an anode current proportional to the frequency difference (F1-F2). Receiver, Fig. 4. The magnetic comparator is similar to that of the transmitter. The frequencies F1, F2 received, are translated in the converter 4a (not shown), to a direct current Jf proportional to F1-F2, which flows through the winding 102, 102<SP>1</SP> and also through the winding 182 of a magnetic amplifier 180. A fixed D.C. from source 44 flows through the windings 103, 103<SP>1</SP>, 183 such that when F1-F2=fo, the basic frequency (zero value transmitted), the resultant ampere turns of each coil pair 102-103, 102<SP>1</SP>-103<SP>1</SP>, 182-183 is zero. The current in the A.C. winding. 184 then assumes such a value as to bias the opposed pentodes 609-610 through transformer 186 to feed equal but opposite currents to the 'indicating control device 47 and the windings 101, 1011. The resultant current in this circuit is thus zero. For any other value transmitted the corresponding current Jf in coil 182 adjusts the output of the magnetic amplifier. This varies differentially the biasing of the valves 609-610 to produce a resultant current J1 in the coils 101, 101<SP>1</SP>, to restore balance in the comparator. This current J1 is proportional to F1-F2. Should proportionality be departed from, the comparator, as in the transmitter, yields a D.C. output ur which produces a current in the coil 181 of the amplifier 180 to restore proportionality.