GB2032191A - Improvements in Electrical Resistors - Google Patents
Improvements in Electrical Resistors Download PDFInfo
- Publication number
- GB2032191A GB2032191A GB7839025A GB7839025A GB2032191A GB 2032191 A GB2032191 A GB 2032191A GB 7839025 A GB7839025 A GB 7839025A GB 7839025 A GB7839025 A GB 7839025A GB 2032191 A GB2032191 A GB 2032191A
- Authority
- GB
- United Kingdom
- Prior art keywords
- resistor
- envelope
- band
- terminals
- electrical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/06—Electrostatic or electromagnetic shielding arrangements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/02—Housing; Enclosing; Embedding; Filling the housing or enclosure
- H01C1/024—Housing; Enclosing; Embedding; Filling the housing or enclosure the housing or enclosure being hermetically sealed
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
- H01C1/148—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors the terminals embracing or surrounding the resistive element
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Details Of Resistors (AREA)
Abstract
An electrical resistor, particularly of high resistance value, is described comprising an elongate resistor body having electrically conductive terminals 3 extending from ends thereof and having an electrically insulating envelope 5 surrounding the body. An electrically conductive band 7 is provided on, and optionally extending through the thickness of, the envelope at a region intermediate the ends and arranged to substantially surround the resistor body whilst being electrically insulated therefrom. The band is arranged to be connected so as to be maintained at substantially the same electrical potential as one of the terminals 3 when the resistor is connected for operation, and risk of leakage current flow across the surface of the envelope, and optionally through the envelope, is thereby minimised or avoided. <IMAGE>
Description
SPECIFICATION
Improvements in or Relating to Electrical
Resistors
This invention relates to electrical resistors and more particularly to electrical resistors having a high electrical resistance value, e.g. above 106 ohm.
In the preparation of high value electrical resistors having resistance values above about 106 ohm, problems arise with regard to the provision of electrically insulating protective coverings for the resistance element of such a resistor. The element must be especially well protected against moisture and contaminants such as grease or dust since such moisture and contaminants would provide a leakage path for electric current across the surface of the resistor and although this leakage path may be of quite high electrical resistance, its value is significant in relation to the electrical resistance value of the element with which it is effectively connected in parallel.Attempts have been made to overcome these problems by enclosing the resistance element in a sealed envelope, glass being particularly favoured for this purpose, the glass envelope being applied in the form of a tube over the resistance element and sealed to the ends of the element where the terminations emerge.
This approach is not wholly satisfactory, since the surface of the envelope can become contaminated as a result of deposition of airborne moisture, dust or grease. This contaminated surface again provides a high electrical resistance path in parallel with the high value resistance element and significantly affects the measured end to end resistance value of the resistor and promotes resistor instability.
It is an object of the present invention to overcome or minimise the above disadvantages.
The present invention provides an electrical resistor comprising an elongate resistor body having electrically conductive terminals extending from ends thereof, an electrically insulating envelope surrounding said resistor body, said envelope being provided, at a region intermediate said ends, with an electrically conductive band substantially surrounding but electrically insulated from said resistor body, said band being adapted to be connected so as to be maintained at substantially the same electrical potential as one of said terminals when said resistor is connected for operation.
In one embodiment, the said band may be provided on the external and/or internal surface of said envelope and suitably comprises a metal strip or wire, or a layer of electrically conductive material deposited on said external and/or internal surface.
In a further embodiment the said envelope may comprise two portions joined by said band, said band preferably extending throughout the thickness of said envelope.
The said envelope may comprise inorganic or organic material, well known in the art, e.g.
plastics, cements, lacquers, glasses or ceramics.
A preferred material is glass, applied in the form of a tube and sealed to the ends of the resistor body or to the terminals.
Advantageously the resistor has an electrical resistance value of greater than 106 ohm, measured between the terminals.
When the resistor of the invention is connected by its terminals to an electrical circuit such that electric current passes through it, then by connecting the electrically conducting band so that it is maintained at substantially the same electrical potential as one of the terminals of the resistor, substantially no electric current flow can occur across the surface of the envelope between the terminals even although the surface of the envelope may be contaminated with matter which would otherwise provide a high resistance leakage path for electric current. The invention thus constitutes a significant improvement in high value resistor technology.
The invention is now described by way of example with reference to the accompanying drawings in which:
Figure 1 shows a perspective view of an embodiment of electrical resistor according to the invention.
Figures 2 and 3 represent sections through alternative arrangements for the resistor of Figure 1.
Referring to Figures 1 and 2, an electrical resistor according to the invention is constructed comprising a resistor body 1 consisting of a cylindrical ceramic substrate having on its surface a film of electrically resistive material, e.g. a film of metal, metal alloy, metal oxide, cermet or carbon, well known in the art. Terminals comprising metal caps 2 and leads 3 are provided, the caps 2 forming an interference fit with the ends of the resistor body 1 and in electrical contact with the resistive film. A helical groove 4 is cut in well-known manner in the resistive film to produce a high resistance value, e.g. 106 to 1014 ohm, measured between the terminals.
An electrically insulating envelope 5, in the form of a glass tube, is slid over the resistor body and sealed to the leads in regions 6 by locally applying heat to cause the glass to melt in those regions.
An electrically conductive band 7 is applied to the external surface of the envelope 5 at a region intermediate the ends of the resistor and such that the band 7 surrounds the envelope 5. The band 7 may comprise wire or metal tape wrapped around the envelope 5 or may comprise a deposited layer of an electrically conductive material such as silver.
The resulting resistor is connected by its leads 3 into an electrical circuit (not shown). An electrical lead (not shown) is also connected to the band 7, e.g. by means of a spring clip, and arranged so that band 7 is maintained at the same electrical potential as one of the leads 3.
The presence of band 7 at this potential means that no leakage of electric current can occur across the surface of the envelope 5, between the
leads 3, in the event that the surface of the envelope became contaminated to the extent that
a high resistance current leakage path would otherwise occur across the surface of the envelope. Thus substantially all of the current through the resistor is carried by the resistive element of the resistor body regardless of the state of the external surface of the envelope 5.
In some circumstances, leakage of electric
current may also occur through the body of the
insulating envelope 5 or across the inner surface
of the envelope 5. This is overcome or minimised
by means of the arrangement shown in Figure 3.
.In Figure 3, parts fulfilling the same or similar functions as those in Figures 1 and 2 are given
the same reference numerals as in Figures 1 and
2. In Figure 3, a resistor body 1 provided with
terminals comprising metal caps 2 and lead wires
3 is sealed inside a glass envelope 5 as previously
described in relation to Figures 1 and 2. The
arrangement in Figure 3 differs, however, in that
the glass envelope 5 is formed of two parts joined together by metal band 7, the metal band 7
extending throughout the thickness of the glass
envelope 5. An example of a suitable material for
the band 7 is copper and this band is joined to the
two'parts of the glass envelope using
conventional glass to metal sealing techniques,
well known in the art. The glass envelope and the
band 7 are spaced from the surface of the resistor
body 1 by means of the caps 2 so that the band 7
is maintained electrically insulated from the
resistor body.
The resistor is connected in circuit as previously described with respect to Figures 1 and 2 and the band 7 being connected so as to be
maintained at the same electrical potential as one of the terminal leads 3 of the resistor. By means of this arrangement, leakage of electric current is
minimised or prevented not only across the
external surface of the envelope 5 between the terminal leads but also through the envelope and across the internal surface of the envelope.
Claims (9)
1. An electrical resistor comprising an elongate resistor body having electrically conductive terminals extending from ends thereof, an electrically insulating envelope surrounding said resistor body, said envelope being provided, at a region intermediate said ends, with an electrically conductive band substantially surrounding but electrically insulated from said resistor body, said band being adapted to be connected so as to be maintained at substantially the same electrical potential as one of said terminals when said resistor is connected for operation.
2. A resistor according to Claim 1 in which said band is provided on the external and/or internal surface of said envelope and comprises a metal strip or wire, or a layer of electrically conductive material deposited on said external and/or internal surface.
3. A resistor according to Claim 1 in which said envelope comprises two portions joined by said band.
4. A resistor according to Claim 3 in which said band extends throughout the thickness of said envelope.
5. A resistor according to any one of the preceding Claims in which said envelope comprises inorganic or organic material.
6. A resistor according to Claim 5 in which said material comprises plastics, cements, lacquers, glasses or ceramics.
7. A resistor according to Claim 6 in which said material is glass applied in the form of a tube and sealed to the ends of-the resistor body or to the terminals.
8. A resistor according to any one of the preceding Claims, having an electrical resistance value of greater than 1 Off ohm, measured between the terminals.
9. An electrical resistor constructed and arranged substantially as herein described and shown in the accompanying drawing.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7839025A GB2032191A (en) | 1978-10-03 | 1978-10-03 | Improvements in Electrical Resistors |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7839025A GB2032191A (en) | 1978-10-03 | 1978-10-03 | Improvements in Electrical Resistors |
Publications (1)
Publication Number | Publication Date |
---|---|
GB2032191A true GB2032191A (en) | 1980-04-30 |
Family
ID=10500065
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB7839025A Withdrawn GB2032191A (en) | 1978-10-03 | 1978-10-03 | Improvements in Electrical Resistors |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2032191A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0482271A1 (en) * | 1990-10-24 | 1992-04-29 | International Business Machines Corporation | Current-to-voltage converter with low noise, wide bandwidth and high dynamic range |
EP2833372A1 (en) * | 2013-07-31 | 2015-02-04 | Forschungszentrum Jülich GmbH | Resistor with reduced parasitic capacitance |
CN105842508A (en) * | 2015-01-12 | 2016-08-10 | 苏州华电电气股份有限公司 | AC voltage divider |
-
1978
- 1978-10-03 GB GB7839025A patent/GB2032191A/en not_active Withdrawn
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0482271A1 (en) * | 1990-10-24 | 1992-04-29 | International Business Machines Corporation | Current-to-voltage converter with low noise, wide bandwidth and high dynamic range |
US5237493A (en) * | 1990-10-24 | 1993-08-17 | International Business Machines Corporation | Current-to-voltage converter with low noise, wide bandwidth and high dynamic range |
EP2833372A1 (en) * | 2013-07-31 | 2015-02-04 | Forschungszentrum Jülich GmbH | Resistor with reduced parasitic capacitance |
CN105842508A (en) * | 2015-01-12 | 2016-08-10 | 苏州华电电气股份有限公司 | AC voltage divider |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |