Patent GB-481851-A (GB)
Title: Improvements in or relating to devices for simultaneously electrically measuring or rendering effective two independently variable magnitudes
IPC: G01R1/30
Filed: 1937-07-05
Abstract: 481,851. Electric control systems. SIEMENS & HALSKE AKT.-GES. July 5, 1937, No. 18695. Convention date, July 3, 1936. [Class 40 (i)] [Also in Group XXXVI] In a device for simultaneously measuring or rendering effective any two independently variable magnitudes by means of a common conductor system, two A.C. potentials in quadrature are produced, their values being dependent upon the magnitudes to be measured; these potentials combine to form a resultant which is applied through a common conductor to a measuring circuit which separately indicates the two components. As shown in Fig. 1, two slide wires 6, 7 are connected in series with a resistance 4 and a condenser 5 respectively across the secondary windings of transformers 2, 3, fed from supply conductors 1. The mid-points of the slide wires 6, 7 are connected through a measuring instrument such as a vibration galvanometer 8. Sliders 6<1>, 7<1> are connected across a diagonal of a bridge containing resistances 9, 10, 11 in three arms, the fourth arm consisting of a variable resistance 12 and a variable condenser 13 in parallel. These are separately varied by the magnitudes to be measured. The resultant potential in the measuring diagonal of the bridge contains two components in quadrature which are separately balanced by the sliders 61, 7<1>, the displacements a, b of the sliders 61, 71 respectively measuring the resistance 12 and capacity 13. In a modification, Fig. 2, two resistance thermometers 19, 20 are connected in series with a condenser 21 and a resistance 22 respectively in two arms of the bridge and are separately measured by the displacements a, b of sliders 15<1>, 16<1> on slide-wires 15, 16 which carry currents in quadrature. In the arrangement shown in Fig. 3, two instruments 23, 24 are controlled by coupling with instruments measuring the magnitudes to be measured. These instruments are each coupled with a moving coil 25, 26 rotatable in the field of its corresponding electromagnet 27, 28. These are excited from supply conductors 1 through a condenser and resistance 33 so as to produce magnetic fields displaced in phase by 90‹. The moving coils 25, 26 are connected in series through the primary circuit of an amplifier 40, and are also connected to contact arms 34<1>, 35<1> sliding on slide wires 34, 35 which carry currents in quadrature, and whose mid-points are connected. The output of the amplifier 40 controls an instrument 41 which automatically adjusts the positions of the arms 34<1>, 35<1>, for example by means of two separately excited induction meter measuring mechanisms which simultaneously operate as phase-dependent zero indicators and as reversing motors, each mechanism driving one of the arms 34<1>, 35<1> through shafts 3411, 3511. The potentials induced in the coils 25, 26 are dependent on the angles through which they have been turned by the instruments 23, 24 and are in quadrature. The instrument 41 automatically adjusts the arms 341, 351 in response to the two components, so that the lengths a, b are measures of the angles through which the instruments 23, 24 have turned. The frequency and potential of an alternating current are simultaneously recorded by the apparatus shown in Fig. 4. The primary winding 42 of a transformer with two secondary windings 43, 44 is connected to the conductors 1 excited by the potential to be measured. The secondary winding 43 feeds a frequencymeasuring bridge comprising resistances 45, 46 forming two arms, the other two arms being formed by a resistance 47 and condenser 49 in parallel and a resistance 48 and condenser 50 in series. The secondary winding 44 feeds a second bridge containing four resistances 51, 52, 53, 54, at least one, 54, of which is dependent upon potential. The diagonals of the bridges are connected in series through the input of an amplifier 40 and contact arms 551, 56<1> moving over slide wires 55, 56 which are connected at their centres and carry currents in quadrature. The amplifier controls an instrument 41 which, as in the apparatus shown in Fig. 3, adjusts the arms 551, 561 so that the deflection of a recording device 60 connected to the arm 55<1> indicates the frequency, and a recording device 61 connected to the arm 56<1> indicates the potential.