Electrical resistors – Mechanically variable – Resistance value varied by removing or adding material
Patent
1983-07-06
1985-07-23
Beha, Jr., William H.
Electrical resistors
Mechanically variable
Resistance value varied by removing or adding material
323298, 323354, H01C 1016
Patent
active
045311110
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a voltage divider.
BACKGROUND
Voltage dividers using thin- or thick-film technology are already known. Such ohmic voltage divider includes resistor through which current flows; they usually are two individual resistors connected by a metal film. The metal film simultaneously acts as the tap for tapping off the desired divider voltage. These voltage dividers have the disadvantage, however, that calibration of the divider resistance to a desired value is possible only by increasing the values of the individual resistors making up the voltage divider. As a result the total resistance of the divider and the distribution of electric current and potential in the voltage divider resistors are varied thereby as well.
THE INVENTION
It is an object to provide a film-type voltage divider which provides an accurately calibrated take-off voltage from a voltage divider tap without, essentially, changing the resistance values of the resistor forming the voltage divider upon calibrating the tap-off voltage.
Briefly, a single coherent film resistor is provided, made, for example, by thick film or thin film technology. The film, for example, of rectangular outline, has an electrical supply conductor and a drainage conductor connected to opposite smaller sides of the rectangle to form at the film, current supply and drainage areas, between which the coherent resistor film extends. The tap is formed as a second resistance film zone, electrically connected to the coherent resistance film zone, between the connection or end areas, the second resistance film zone then being calibrated to provide the desired tap-off voltage, independently of the value of the first or main film zone. A tap off conductor or electrode is electrically connected to the second resistance film zone.
The voltage divider according to the invention has the advantage that by shifting the alteration required for calibration into the second resistance zone belonging to the tap, a predetermined equipotential line can be selected at the take-off electrode of the tap without thereby having to substantially vary the actual voltage divider resistance or its potential distribution. A particularly advantageous type of alteration, effected in the second resistance zone for the sake of calibration, is the formation of a cut, by laser or sand blasting. In another advantageous solution to the calibration problem a single, coherent voltage divider resistor is used and a cut partially separates the coherent resistor film to form these and the second zone which is also used at the same time as a tap.
DRAWING
Exemplary embodiments of the voltage divider according to the invention are shown in the drawing and explained in further detail in the following description. Shown are:
FIG. 1, the basic variant of a voltage divider according to the invention, which is realized by thick-film technology and is seen in a plan view;
FIG. 2, the equivalent circuit diagram for the voltage divider shown in FIG. 1; and
FIGS. 3-8, further variants of voltage dividers according to the invention, realized by thick-film technology and seen in plan view.
DESCRIPTION OF THE INVENTION
The voltage divider shown in FIGS. 1 and 2 includes an ohmic voltage divider resistor R.sub.1 (FIG. 2) connected to have electric current flow through it. This voltage divider resistor comprises a single coherent first resistance film 10 realized by film technology, a connection conductor 11 serving to supply electric current and a connection conductor 12 serving to drain, or carry away electric current; the connection conductors 11 and 12 are formed as conductive tracks (FIG. 1). The first resistance zone 10 forms a rectangular area, the length of which is greater than its width. The connection conductors 11 and 12 are attached to the narrow sides of this rectangular area and along these narrow sides they overlap the first resistance zone 10.
A tap serving to tap off the desired divider voltage is also provided. This tap comprises a second resistance zone 13 made by film technolog
REFERENCES:
patent: 4100525 (1978-07-01), Denes
patent: 4284970 (1981-08-01), Berrin et al.
patent: 4475099 (1984-10-01), Praria
Goebel Ulrich
Schmidt Lothar
Beha Jr. William H.
Robert & Bosch GmbH
Sterrett Jeffrey
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