US2320662A - Electrostatic voltmeter - Google Patents

Description

June 1, 1943. R. SCHROEDER ,3

ELECTROSTATIC VQLTIMETER Filed Jan. 23, 1939 2 Sheets-Sheet 1 Inventor:

Attorney June 1, 1943. RLSCHROEDER ELECTROSTATIC VOLTIMETER 2 Sheets-Sheet 2 Filed Jan. 25, 1959 fin Fig. 45

2 I lnvenzor: fliofiagrdfcfmacdm Aflomey Patented June 1, 1943 ELECTROSTATIC voLrMn'ma 1 Richard Schroeder, Aachen, Germany; vested in the Alien Property Custodian Application January 23, 1939, Serial No. 252,510 in Germany January 22, 1938 4 Claims. (01. 371-99 (Granted under the provisions of sec. 14, act of.

Electrostatic voltmeters have considerable advantages as compared with all other voltage measuring devices, since they operate practically without loss substantially independently of frequency with direct and continuous voltage. Through the development of high-frequency technique a number of questions relating to instruments of this type have become acute, which hitherto were of secondary importance. In partic ular the magnitude of the capacity plays an important role. With increasing frequency the capacity current increases linearly so that with instruments having higher capacities the limit of usabilityis quickly reached. Since the forces in theelectric field at low voltages are very small, the expedient hitherto adopted was to use in the constructions large capacities in order in this way to obtain the required torque. Large capacities imply large surfaces, and consequently considerable weight or the moving parts. This implies in turn a long period for the moving part to come to rest. Oscillations lasting from to 30 seconds are not uncommon with instruments of this kind. The new voltmeter is intended to overcome these serious deficiencies in order to provide an instrument which gives a; suiiiciently rapid indication with low capacities. The new method of electrostatic voltage measurement is based upon the iollowing considerations.

Since the electric forces giving rise to a rotary movement are only very small and on the other hand no large surface is desired, and moreover a firm mounting. must be obtained, the gravitational force is made useof as a force additional to the electrical force.

Fig. 1a is a perspective view of an embodiment of this invention.

Fig. lb is a corresponding plan view.

Fig. 1 is a corresponding schematic side view.-

. considerably influenced.

March 2,1927; 357 0. G. 5)'

scale 3 (Figs. 1-4). the electrodes by way of the connectors n.

It the centre of gravity 0 of the system is displaced upwardly out of the axis of rotation d according to Fig. 1, and then an electric field is impressed between the electrodes a and b, a rotational movement will take place the angle of rotation being greater than if the centre of gravity lay in the axis. The more the centre of gravity is displaced upwardly the greater will be the angle of rotation when other conditions remain the same. that is with the same surface and the same restoring force. This does not, however, continue without limit, but only until the so-called point of instability is reached. From this point onwards the restoring force of the twisted ribicon is no longer capable of restoring the system to its original position. The new method uses the range of locations of the centre of gravity up to the point of instability. The great advantages are that the surfaces can be kept small, in the case of ribbon suspension a larger crosssection can be used and in the case of axial mounting a stronger spring can be employed, moreover in consequence of the smaller masses a more rapid indication can take place. It is in many cases desired to modify the approximately quadratic form of the scale. In. Figs. 2 and 3 is shown such a possibility. If the cooperating electrode is not extended in concentricity with the movable electrode, the form of the scale becomes more linear. In Fig. 4 is shown an embodiment in which both electrodes are movable. In this way also the form of the scale can .be

I claim:

1. An-electrostatic voltmeter comprising a pair of relatively movable electrodes, one of said electrodes being rotatable around a substantially horizontal axis, being normally yieldably suspended in juxtaposition with the other electrode, being normally substantially oifset from its axis of rotation towards the other electrode, and the.

center of gravity of said one electrode bein slightly above and ofiset from its axis of rotation towards said other electrode, tension means substantially horizontally suspending said one electrode in juxtaposition with the other elecspring substantially disposed in the plane of the arm of electrode b, normally retaining said arm in substantially level position and serving to restore such position in opposition to the electrostatic iorce playing between electrodes 1: and b.

Means registering relative displacement be tween the electrodes are indicated by a voltage trode, means for applying an electrostatic difference of potential between the relatively movable electrodes, and a voltage scale placed to indicate relative displacement between said electrodes, and a pointer operatively connected. with said one electrode and arranged to play on said scale.

2. An electrostatic voltmeter comprising a pair Potentials may be applied to 4 or relatively movable electrodes, one of said electrodes being rotatable around a substantially horizontal axis, being normalb substantially oi!- set from its axis of rotation towards the other 4 electrode, and the center of gravity or said one electrode being slightly above and offset from its axis of rotation towards said other electrode, restoring means placing said one electrode into a position in which it faces the other electrode when at rest, means for applying an electrostatic dlimeans tor applying an electrostatic difierence of potential between the relatively movable electrodes, restoring means applying a torque counter to the action of gravity 01' said one electrode and oi. any electrostatic force when said one electrode is deflected by a difference of potential applied to said electrodes, and a pointer operated by said one electrode and a voltage scale placed to indicate relative displacement between said electrodes.

4. In an electrostatic voltmeter, a pair of trunnions, a spring leai horizontally extended between said trunnions, a first electrode arranged at a point horizontally removed from said spring leaf, 9, second electrode oscillatably suspended by said spring leaf at a point removed from its center of gravity and extending from said point substantially horizontally towards said first electrode, connecting means for applying different potentials to said electrodes, torsion of the spring leaf by deflection of said second electrode under a difference of potentialsbetween said electrodes setting up a torque ior restoring said second electrode to a normal position after the diiference of potential between said electrodes has been removed, and a voltage scale having a pointer operatively connected with said second electrode and placed to register relative displacement between said electrodes.

, RICHARD SCHROEDER.

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