FR2684187A1 - Improvements to the structure of leaf (foil) electrometers - Google Patents

Abstract

The invention relates to electrometers consisting of a movable conducting strip repelled by a fixed conducting strip, and using organic materials with a very low density and good mechanical strength, even when thin. The movable strip (1) is made conducting by applying a layer of graphite to one face and is mounted on a fixed strip (2) by a very fine wire (3). The graphite-coated face of the movable strip faces the fixed strip. The device according to the invention may be incorporated in an ionisation chamber. The fixed strip will be connected to an internal collecting electrode, with the casing forming the external electrode. Once the electrodes are charged, they will be sensitive to external radiation and the movable strip will indicate the radiation dose absorbed by the apparatus. Because this system is made of organic materials, it will be possible to indicate directly, by simply reading the position of the movable strip over a fixed scale, the radiation dose absorbed by the remaining organisms in the same environment as the apparatus described.

Description

IMPROVEMENTS TO THE CONSTITUTION
OF TAPE ELECTROKETERS
The object of the present invention is to improve the performance of tape electrometers for the measurement of very low electrostatic charges.

 In the field of these electrometers consists of a movable conductive strip repelled by a fixed conductive strip or by two movable conductive strips which repel each other when they are brought to the same potential.

 Qn has sought for the constitution of ribbons different materials characteristic by their low masses such as aluminum, gold or metallized plastics etc ...

 However, these materials presented processing difficulties and their masses, however small, influenced the precision and reliability of the measurements of the device.

 The present improvement relates to the use of a material of very low density, used by extremely simple tools and making it possible to produce electrometers of very great sensitivity and reliability.

 The material used is an expanded plastic material of the polystyrene, polyethylene, polyuretane type, etc., with good mechanical strength even with a small thickness.

 It is possible to cut this material according to several methods.

In the present case, we cut a block of expanded polystyrene using the device of Figure 1.

 Desorintion of the aonereil: a rigid and insulating support (1) fixed door on fields two metal stirrups (2) and (3) between which is stretched a resistant wire (4). A tension spring (5) ensures constant tension of the wire, even when the latter is hot. This wire is very slightly inclined towards the left giving to the blade which it will cut, under the action of the heat provided by an electric source, the form indicated by figure 2. The fusion of the material caused by the hot wire hardens the surface of the cut blade. One of the faces of this blade is then made conductive by graphitation, cathode projection or any other means.

This blade (6) is then cut, mechanically for example, into thin equal tapes as shown in Figure 3. The side faces will remain white to facilitate reading on the black graphite background of the measuring device.

 Figure 4 specifies the mounting of the movable blade (6) on the fixed blade (On the version presented, a very fine latex thread (8) is bonded to the fixed blade (7) at points (9) and (10) , a cutout (11) having been previously made in the fixed blade. The movable blade (6) is then glued to the latex wire, in its center, with the conductive face facing the fixed blade. ) of the movable blade protruding from the latex thread will be used to counterbalance the left side. The latex thread and glue assembly is made conductive.

 The fixing of the movable blade on the fixed blade can be done in any other way: axis between two straps, the axis being integral with the movable blade and the straps of the fixed blade or vice versa, sleeve rotating on a wire, movable blade, not bevelled and on which we will have fixed a counterweight which will also serve as a benchmark S the placement of the latex thread etc ...

 Figure 5 gives an example of application of this electrometer to a radiation detection device. An ionization chamber consists of an external electrode (13) and an internal collecting electrode (14) to which the fixed blade (7) of the electrometer is fixed.

The fixed blade assembly f collecting electrode can be manufactured in a single monolithic piece. By switching on, for a short time, the device under tension, the collecting electrode and the fixed blade will be electrically charged and the movable blade will be repelled by the difference in polarity. As radiation acts on the ionization chamber, the charge of the collecting electrode will decrease and the movable blade (6) will approach the fixed blade (7). The displacement being appreciated on a scale of reading (allowing to know the dose o to which the device will have been subjected since the moment of powering up. An alarm device can be installed to indicate, by any system (audible signal , indicators ...), the discharge of the collecting electrode.

Claims (3)

 realization of the mobile elements of these electrometers.  by the use of materials of very low densities for the  1 / Process for the improvement of S tape electrometers characterized 2 / A method according to claim l characterized by cutting  these materials, the shape of the blades obtained, their conductivity  and their attachment to the fixed element. 3 / A method according to claim 1 characterized by the use of  this electrometer in a dose measurement ionization chamber  of integrated radiation.