DE1916891U - NONLINEAR FUNCTIONAL POTENTIOMETER WITH SEMICONDUCTOR RESISTANT LAYER - Google Patents

Description

PA51073HB.7.W Xl

17th July 1964

lG. Stuttgart, -24

/ 2Vc

Zeiss Ikon AG. Stuttgart, the-

- to Pa.1229 -

"Calibrated function potentiometer with half-it answer first and foremost "

A / £ c / eri4f>) O

The ■ refers to function potentiometers that a high degree of accuracy at low manufacturing costs and ensure operational safety. Such potentiometers are particularly suitable for regulating the photocurrent in exposure meters, especially for cameras with automatic exposure. With such devices there is often a desire to increase the photocurrent in certain discrete steps change, each corresponding to a f-stop. To take the photocell characteristics into account, it is then it is necessary to keep a series resistance variable from stage to stage according to an empirical law. Special in the case of bridge circuits with photoresistors, this Purpose of a function potentiometer with a control curve in the manner of an exponential function.

For similar tasks, wire potentiometers with linear winding sections have been used up to now, but the In addition to relatively large dimensions, they also have the disadvantage that the required empirical course of the resistance can only be reproduced in a rough approximation. High resistance values can only be achieved with extremely thin wires, which easily give rise to disturbances. Potentiometers with an injection-molded resistance layer are also used.

borrowed, their specific resistance, for example, by non-uniform Movement of the potentiometer track relative to the Spray gun was held changeably. With these potentiometers, the reproducibility caused great difficulties; therefore quite large tolerances had to be accepted. In addition, the contact between the semiconductor layer and the potentiometer track are often an additional source of interference.

In accordance with the present, the aforementioned difficulties become avoided that the resistance of the potentiometer is partially covered with resistance material of different, but within each section constant resistivity is covered, and that for approximated equidistant division of the sensitivity scale required Control curve simulated solely by changing the width of the resistance layer within the individual sections will.

This measure improves the reproducibility quite significantly. To produce a flawless Contact between current collector and layer, the layer is underlaid with a fine metal grid, which is either is painted by the pantograph directly or via a metallic contact grid.

As an example to explain the

which describes a potentiometer for use in a bridge circuit with photoresistor according to FIG. R ₁ denotes the photoresistor illuminated by light rays L, Rp the step-wise variable function potentiometer, R and R. are fixed resistors, G a galvanometer and B a battery for operating the circuit. The individual resistance levels of the potentiometer Rp are assigned to the film sensitivities to be taken into account, which in the example cover the range from 2 to 30 DIH. Every three resistance levels correspond to a f-stop at 3 ° DIN, so that with the potentiometer a total of 9 1/3 f-stops or

Q -XZ

a range of object brightnesses of 1: 2 '^ = ι: 645 is recorded. Rp is now measured in such a way that the galvanometer G is de-energized when the photoresistor R ₁ receives the amount of light L belonging to the set sensitivity level from the object. The relationship then exists between Rp and R ₁

^R 2 ⁼ RT ^R 1

Since R ^ and R * are constant, this means that the values Rg the occurring V / resistance values R .. are modeled proportionally must be. FIG. 2 now shows the required assignment of the resistance values for a specific type of photoresistors Rp for the sensitivity levels χ = 3 to χ = 30 ° DIN reproduced in a semi-logarithmic representation. The task is therefore to simulate this curve with a reliably working function potentiometer.

The function potentiometer according to the is in Fig. 3a shown in section and in Fig. 3b in plan view. The basic component is the threaded bushing 1, which with the help of the nut can be fastened in a bore in the wall, for example of a light meter. Fig. 3a further shows the actuation button 3 with sensitivity ranging from 2 ° to 30 ° DIN sscale, also the axis 4 connected to 3 and the socket 5 into which the current collector 6 is embedded. · The carriers of the resistance layer 7 are the insulating material sectors 8 designated in FIG. 3b with I, II, III and IV These sectors are connected to the socket 1 by screws 9. There are six full and six on each sector radial boundary lines two half guide strips 10. All Conductive strips are covered with the resistance layer 7 and outside this layer interspersed with bores into which the contact rivets 11 are let. Put the rivets also establish the conductive connection between neighboring sectors and are swept by the pantograph 6. The number of Contact riveting corresponds to the number of intended sensitivity levels. Your assignment to sensitivity The scale is indicated in FIG. 3b by the sensitivity in brackets s indications (2 °) to (30 °) DIM "illustrated The soldering lugs 12 and 13 are used to supply power, namely 12 connected by the flexible strand 14 with the wiper 6, while 13 with the conductive strip 2 ° DHT of the sector I in connection stands.

For the sake of clarity, in FIGS. 4a and 4b one of the

identical sectors I to IV shown separately, as a semi-finished product without contact rivets. The resistance layer is noticeably boiling 7, the insulating pad in the form of a sector and the conductive strips 10. The conductive strips encompass the bores 15, in which the contact rivets 11 are inserted according to FIG. 3 after assembly. Can be seen in Fig. 4b Conductive strips 10a and 10b at the edge of the resistance layer are only half-width, in order to measure the total resistance to allow the resistance layer of the sector.

By dividing the control curve of the function potentiometer into four sub-sections, it is achieved that only the fourth part of the entire control range is used for each sub-section of the resistance layer. While according to Fig. 2 the resistance must have a control range of 28 a: 1540 Λ = 1.55, the sub-ranges only have a resistance variation between 1: 2.43 and 1ΐ3 · 08. This can be seen from the following table, which defines the scope of regulation R for the four sectors. : E and the resistance component R - R _min allotted to each sector.

sector 28 ^R min ^: Max 2.43 Max - ^R min I. 68 : 68 = 1: 2.66 40 Λ II 181 : 181 - ι · 2.76 113 Λ . III 500 : 500 = 1: 3.08 319 Λ IV : 1540 = 1: 1040 a

The resistance variation is given by the potentiometer achieved in that the width of the resistive layer is changed in the same ratio. The decisive one Progress over the known is that each sector with a resistance material of uniform resistivity, i.e. uniform composition of the semiconductor material, can be demonstrated. E.g. it is possible to coat each sector using a stencil with a continuously variable width according to the spraying process, or to print the resistor material using a cliché of the appropriate shape. Because the shape of the control curve is determined by the geometric shape of the layer, only needs to be checked during production, -whether the measured between the guide strips iQa and 10b in Fig. 4b

the

sene total resistance of each sector / values R - R required in the table. accepts. As a result, the manufacturing costs for one sector of the function potentiometer do not significantly exceed the manufacturing costs of semiconductor fixed resistors. With regard to the accuracy and reproducibility of the control curve, the usual tolerances for solid-state semiconductor resistors of 17 $ to 5f ° can be maintained with comparable effort. All four sectors can be manufactured using the same process, using the appropriate spray or printing stencil that corresponds to the resistance ratio R _m . : R _{mav of} the sector concerned

min nothing

is equivalent to. It is only necessary to ensure that the specific Resistance of the semiconductor material in each sector is chosen with such a value that the It. Table for

resistance values R required for the sector concerned

Max

^R min ^ ^{reach it} is. In addition, the potentiometer must be operated with a series resistor of 28Λ, which, according to FIG. 2, corresponds to the lowest sensitivity to be taken into account of 2 DIIT.

The conductive strips 10 with which the resistance layer 7 is underlaid ensure defined potential relationships and perfect contact. The divided guide strips 1Ga and 10b on the fringes of the sectors also have two other tasks. First, they allow perfect control of the total resistance R - R. of each sector and, secondly, they facilitate the power connection between neighboring sectors. For example, the connection between the sectors, as shown in FIG. 3, can be through one of the two sectors common contact rivet can be made. The guide strips 10 can be by vapor deposition, spraying or printing Manufacture metal layers. The known production methods for printed circuits can also be used, so that they are cheap Conditions for the cheap mass production of these potentiometers are given.

The function potentiometer according to FIGS. 3 or 4 has just as many sensitivity levels as guide strips and Contact rivets are provided. However, a design in which the number of guide strips the Number of sensitivity levels to be taken into account

8th -

for example by a factor of 2. In this version the contact rivets and the contact point between the conductive strips and the current collector are expediently dispensed with outside of the resistance layer only galvanically reinforced .

Sin sector with this inventive variant of the Leitstrei-

insulating fen is shown in FIG. On the Sicilian pad S the conductive strips 10 with the galvanic reinforcement 16 are located. The resistance layer is denoted by 7. In In this case, the conductive connection between the sectors is made by soldering the edge of the conductive strips 10a and 10b at the end of the resistance track with the corresponding ones that follow Sectors manufactured. With this design, a certain amount is not only achieved by eliminating the contact rivets Cost savings, but you also have the option of changing the distance between the engraving lines Sensitivity scale different slopes of the photo elements or to compensate for photoresistors. Should the potentiometer are used, for example, for photoresistors of greater steepness, the control curve must be steeper as shown in FIG. This can be achieved by increasing the distance between the graduations on the control button. Conversely, by compressing the scale division, the control curve can be adapted to photo elements or photo resistors low steepness can be achieved.

Claims (6)

RA.51073MIlΆ ■ claims 1. Non-linear function potentiometer with semiconductor resistor layer, preferably for regulating the photo current in photoelectric light meters, especially for Cameras with automatic exposure, characterized in that QlT. Ö that the resistance of the potentiometer otadt in sections Resistance material of different, but constant specific resistance within each section exists, stKJsktxisi ^: and that the for approximately equidistant division the control curve required by the sensitivity scale variable width of the resistance layer is simulated within the individual sections. 2. Function potentiometer according to claim 1, characterized in that that the resistance track in the form of a ring divided into sections of variable width to a preferably flat insulating pad is applied, which is composed of as many sectors as resistor sections are provided. 3- function potentiometer according to claims 1 or 2, characterized characterized in that the resistance layer is underlaid with narrow, approximately equidistant conductive strips, which the conductive connection between the current collector and the resistance layer produce outside of the shift. - 10 - April 12, 1965 M ^ - 10 - 4. Function potentiometer according to claims 1 to 3, characterized in that just as much guide strips or contact rivets are provided as sensitivity levels are required. 5 · Function potentiometer according to claims 2 to 4, characterized characterized in that the resistance tracks of the sectors on both sides finish with guide strips, which according to composition of the potentiometer serve to establish the electrical connection between to establish neighboring sectors. 6. Function potentiometer according to claims 1 to 3, characterized in that the number of guide strips is greater, are provided as sensitivity levels, and that the distance the graduation marks of the sensitivity scale on the operating button is adapted to the steepness of the characteristic of the photo element or photo resistor used. Hlnvtffllr: Dicro Ur.u. ' - ■ -la-Brrfrnd protection claim) is the last one submitted; it deviates from the value version cK: -r ι · -: · ::> ιη ';: .'- ι civ / ^ etahfen documents. The legal Bi.-bufun] c 'deviation has been checked, the original: jii' -, ic insert ί;,! Ι * η '..''.! SfK ^ en are in dt> n An.tsuki 'sn. £; ■■> \:, - <: n l'jciwstii't without Nsshw§is a rechilicher. Internal ς ^ buhrenfrel can be viewed. On request, liljivo.i oji.h Fotokiylen oder Film «negatives will be delivered at the usual prices. German Patent Office, Gebrauohimuittritill ·.