DE1113504B - Voltage divider with high resolution - Google Patents

Description

There are three-pole voltage dividers known to change the division ratio when they are set the output resistance remains the same. Such a voltage divider can be in a simple form only differ from the usual resistance provided with an adjustable pick-up in that there is a series resistance between the tap and the load resistance, which is determined by the setting changes so that it compensates for the otherwise resulting changes in the output resistance.

The invention is to provide a voltage divider with high resolution, the z. B. for regulating and measuring purposes or to generate analogy values for the purpose of monitoring, Regulation or invoice is suitable. For the purposes mentioned, it is essential that that the output resistance of the voltage divider remains unchanged.

The voltage divider with constant output resistance according to the invention is characterized in that at least two known three-pole divider units, each for changing the Division ratios can be set without changing the output resistance of the unit, switched one after the other where the division ratio of the voltage divider is equal to the product of the division ratios of the divider units and the output resistance is independent of the unit settings.

The invention is illustrated in the drawings. It shows

Fig. 1 shows a simple voltage divider, which the voltage divider according to the invention as a component may contain;

FIG. 2 shows an equivalent two-terminal network for the circuit according to FIG. 1;

FIG. 3 shows the symbolic designation for the voltage divider according to FIG. 1;

Figs. 4 and 5 show equivalent two-pole connections of the circuit of Fig. 1;

FIGS. 6 to 10 show examples of voltage dividers which are composed of voltage dividers according to FIG. 1, wherein the voltage divider according to FIG. 6 consists of simple voltage dividers connected in parallel and the 7 are composed of simple voltage dividers in series connection. Fig. 8 shows a simple analogy device, and Figures 9 and 10 show alternative embodiments of one Voltage divider with four decade levels.

For the sake of simplicity, the figures and the text deal only with the DC case. However, the generalization to the AC case can be voltage divider
with high resolution

Applicant:

Svenska Aktiebolaget gas accumulator,
Lidingö (Sweden)

Representative: Dipl.-Ing. W. Mouths, patent attorney,
Frankfurt / M., Börsenstr. 17th

Claimed priority:

Sweden of July 22, 1957 (No. 6847/57)

and February 21, 1958 (No. 1717/58)

Nils Arvid Norman Björk, Lidingö (Sweden),
has been named as the inventor

can be carried out directly by replacing the direct voltages with alternating voltages and the resistances are understood as apparent resistances.

1 shows a three-pole voltage divider which consists of the three two-pole connections A, B and C, arranged in a star connection, with the variable resistances r _a , η and r _c . The input terminals of the voltage divider are α and b, the output terminals c and b. A voltage source with the constant open circuit voltage E and the constant output resistance R _{0 is connected to} the input terminals. The output voltage at no-load is U ₀ .

According to Thevenin's theorem, the voltage divider, viewed from the output terminals, can be regarded as a two-terminal network as shown in FIG. The output resistance of this dipole is denoted by R and its open circuit voltage is denoted by U _0. From Fig. 1 it follows directly:

U _n = E-

η __

R ₀ + r _a + η (R ₀ + r _a ) η

= + ro.

R ₀ + ιό, + η

For the ratio of the open circuit voltage of the voltage divider to the voltage source, the

109 687/173

I 113 504

3 4

Designation χ = U ₀ JE introduced, and the setting It is provisionally assumed that the voltage

of the voltage divider is called χ. From the sliding divider units disconnected from the input terminal α it follows that (1) and that each unit is instead connected to one of them

associated voltage source with the constant

_x ^r JL ; (0 <x <l). (3) ⁵ voltage E is connected. This can be done without

R ₀ + r _a + Tb '~~ ~~ Change in the remaining voltage and current values

ratios- are carried out. After that, each will

By inserting equation (3) into the equation unit with its equivalent two-pole as shown in FIG. 5, equation (2) is replaced. Seen from the output terminals c, b ,

ίο the composite voltage divider appears

R = x (R ₀ + r _a ) + rc- (4) as the parallel connection of the η current sources X ₁ EjR ₁ ,

x _a E / R ₂ ... X _n EfR _n as well as the η connected in parallel

It is assumed that the constant load resistances A ₁ , R ₂ . .. R _n . The output resistance resistance R ₁ between the output terminals of the composite voltage divider is therefore

Voltage divider is placed. From the equivalent 15 _ _{n /} " _VR , i / n _w - constant

The circuit of FIG. 2 follows immediately that the ^R ~ W *! + ¹ I "* + ■ ·· + VRn) - constant,

output voltage (7)

η η

U = U ₀ = χ E- (5) while the short-circuit current has the following value:

R + R ₁ R + R _{1 20th}

will. h = Xi EIR ₁ + X ₂ E / R ₂ - \ (- X _n E / R _n . (8)

So that the voltage divider of load faults

should be free, the output voltage U must be the input The open circuit voltage results from

position χ be proportional. From the equation (5) U = RI (9)

one sees immediately the condition for this: 25 ° '

η _, » _{Λ t} from which the attitude of the compound

Voltage divider gives:

A voltage divider with constant output resistance is free from load errors. _ J ^ _ _χ J ^ _ , _χ J ^ <... ι _x JL

From what has been said, it follows that the details 3 ° E ¹ R ₁ ² R ₂ " Rn of the design of the voltage divider qq ^ are irrelevant with regard to the conditions on the output side. It is therefore justified for It is clear that the composite To use the voltage divider the symbolic three-pole after divider by a single voltage divider Fig. 3, wherein the 35 can be set within the block, the setting of which is exposed to the value χ according to characteristic quantities jc and R. Equation (10) and its output resistance the Der Output resistance R _{0 of} the voltage source has the value R according to equation (7). This span of the voltage divider is adapted, in addition to the voltage divider can only be _{noted the output resistance -R 0} = O input terminal α . If R ₀ = 0, below- the voltage source However, this note remains. 40 This clamping

The equivalent two-terminal circuit according to FIG. 2 of the voltage divider, which can be used as part of a divider according to the invention, is shown in FIG. 4 using the normal voltage divider, open circuit voltage xE instead of U ₀ . The equi is called adding voltage divider, valente two-pole can also be understood as a current source with At least two resistors R according to the invention in a short-circuit current χ E / R and the output 45 composed voltage divider. Voltage divider units with constant output resistance

Let the assembled voltage divider be first connected one after the other. In doing so, the individual is discussed and attention is drawn to the well-known fact of the composite voltage divider that if the voltage divider units are connected in parallel to a voltage divider unit equal to the product of the settings of the span such voltage divider units. Such a voltage divider composed of η on the voltage input side with a resistance-free voltage divider unit is connected source, the setting of the combined voltage shown in FIG. At the input terminals a set voltage divider a sum of elements and b is a voltage source with the open circuit, each of which is dependent on the setting of a corresponding voltage E and the output resistance R ₀ . The voltage divider unit is proportional. 55 voltage directly at the voltage source

Such a composite voltage divider voltage divider is adapted to the output resistance R ₀ , is shown in FIG. The constant voltage E and each of the remaining voltage dividers is placed between the input terminals α and b . input resistance of the previous voltage - the open circuit voltage at the output terminals c divider of the series circuit is adapted, and b is U ₀ and the output resistance R. The 60 First, the η voltage divider units connected to the voltage source have the voltage divider settings through its equivalent two-pole Χχ, χ ₂ . .X _n and the output resistances R ₁ ^ R ₂ .. .R _n - replaced according to FIG. The voltage divider units are all matched to the voltage divider connected to the voltage X ₁ E in series resistance R ₀ = 0 of the voltage source connected to the resistor _{R 1} . It has to be shown, first, that R = constant, 65 found. By repeating the process, the second is the value that is given for setting the third voltage divider to the voltage X ₁ X ₂ E in a composite voltage divider, ie for χ = CZ ₀ / ^ series connection with the resistor R ₂ It follows from this that the initial

voltage when the composite voltage divider is idle has the following value:

U ₀ = X ₁ , X ₂ ... X _n E, (11)

from what the setting

χ = Jc ₁ , X ₂ ... X _n , (12)

is the initial resistance

R = R _n . (13)

10

It is clear that this composite voltage divider can be replaced by a single voltage divider with the setting χ according to equation (12) and with the output resistance R according to equation (13). This voltage divider can be matched to any output resistance R _{0 of} the voltage source.

This composite voltage divider can be called a multiplying voltage divider.

The above composite voltage dividers retain those for the voltage divider units essential property of the constant output resistance. It is therefore possible with these assembled voltage dividers as structural units to assemble new voltage dividers in exactly the same way, how the adding and multiplying voltage dividers are derived from the voltage divider units put together. The wide range of possible variations of this process results in a large number of applications for voltage dividers of this type, examples of which are given.

Fig. 8 shows a simple analogy device for computational purposes, which is composed of seven voltage dividers. All voltage dividers have the output resistance R and are matched to an output resistance of the voltage source with the value R ₀ = R. Some of the voltage dividers (X ₁ , x ₂ , X ₄ , x ₅ ) are connected to the constant voltage E, and the constant resistor R must therefore be connected upstream of them. The other voltage divider are arranged with the adding voltage dividers connected to the output resistor Rfi in succession circuit, and this must therefore be of the constant resistor Rfi be installed. The setting of the composite voltage divider results directly from equations (10) and (12):

χ = [(x j / 2 + x _2/2) X3 / 2 + (x _4/2 + x _5/2) x _6/2] x ₇ (14)
or

they can be used as building blocks to assemble different types of analogy devices be used.

FIGS. 9 and 10 show alternative embodiments of a voltage divider with four decade stages. The voltage divider according to FIG. 9 comprises four voltage divider units with the output resistance R ¹ . By connecting the resistors 9 R ¹ , 99R ¹ and 999 R ^{1 in series} , the output resistances of the three last stages 10R ¹ , 10R ¹ , 100Oi? ^1st The output resistance of the composite voltage divider results from equation (7)

R = R ¹ I (I + 0.1 + 0.01 + 0.001) = R ¹ IhIU, (17)

while the setting is calculated from equations (10) and (17):

_x = ( _Xl + 0.1 X ₂ + 0.01 x ₃ + 0.001 X ₄ VUIl. (18)

The resistors 99 R ¹ and 999 R ¹ can assume uncomfortably high values in certain cases. In the embodiment according to FIG. 10, no resistance need be greater than 9 R ¹ . Stage 3 is followed by a voltage divider with a fixed setting of 0.1, while stage 4 is followed by two such voltage dividers. All voltage dividers have the output resistance R ¹ , but the output resistance of the last three stages is 1Oi? ¹ because of the series connection with the resistor 9 R ¹ . The output resistance of the composite voltage divider becomes

R =

+ 0.1 + 0.1 + 0.1) = i? 71.3, (19)

45

1
4th

+ (.Xi + X

X ₇ ■ (15)

The output resistance is R, so the voltage across the load R _{1 has} the following value:

U = xE

R + R ₁

(16)

The fact that the voltage divider units have the same output resistance and matched the same output resistance of the voltage source and the setting results in
each = (JC ₁ + 0.1 X ₂ + 0.01 X ₃ + 0.001 X ₄ VU. (20)

Claims (2)

PATENT CLAIMS: 1. Voltage divider with constant output resistance, characterized in that at least two known three-pole divider units, each of which can be adjusted to change the division ratio without changing the output resistance of the unit, are connected in series, the division ratio of the voltage divider equal to the product of the division ratios of the divider units and the output resistance is independent of the settings of the units (Fig. 7). 2. Voltage divider, characterized in that it consists of voltage divider groups in parallel or Sequential circuit is composed, each of which is composed in the same way from similar subgroups or is composed of simple voltage dividers, with at least one voltage divider group is designed according to claim 1 (Fig. 8 to 10). Considered publications:
German patent specifications No. 843 433, 730 425. 1 sheet of drawings © 109 687/173 8.61