SU849233A1 - Resistorized voltage divider - Google Patents

Description

(54) RESISTOR VOLTAGE DIVIDER

one

The invention relates to electrical measuring equipment and can be used in analog computers for performing the operation of dividing analog signals.

A resistor voltage divider is known, comprising a set of resistors connected to a star, with each resistor selectively using switches can be connected either to a single terminal of the reference-source. voltage, or to another, the potential of which is taken as zero. The output voltage is removed between the point of zero potential and the top of the star resistors. Parallel divider has variable input and constant output impedance 1.

The disadvantages of this device are the inconsistency of the input impedance, the influence of the transient resistances of the switches, which eliminates the possibility of using contactless transistor switches in precision devices, the need to select resistors for TKS. Within one decade of resistance and between decades. In addition, a large number of resistors of different nominal values causes the bulkiness and laboriousness of the self-verification divider.

The closest to the invention is a resistor voltage divider containing an input decade of resistors, a multi-position switch, n-movable contacts of which are connected to the terminals of the input resistor 10 resistors, the extreme terminals of the input decade of resistors are the input of a voltage divider, an operational amplifier covered by a negative circuit feedback, non-inverting input of which is connected to the first moving contact of the multi-position switch 2,

The disadvantages of the famous divider

20 imply a large division error and self-verification complexity. In addition, the resistive divider does not have a constant output impedance, since the output voltage is removed from different stages of the output decade of resistors. The purpose of the invention is to improve the accuracy and achieve a constant input and output resistor of the resistive voltage divider.

The goal is achieved by introducing the first, second, third, and fourth large-scale resistors into the divider, and an additional amplifier covered by negative feedback, the non-inverting input of which is connected to the second moving contact of the multi-position switch, the first fixed contact of the multi-positioning switch is connected to the zero potential bus, the first the terminals of the first and second large-scale resistors are connected to the outputs of the main and additional operational amplifiers, respectively, and volts rye conclusions are combined and output voltage divider, the first terminals of the third and fourth resistors connected to the scaled inverting inputs of the main and additional operating forces gels, and second terminals coupled and connected to zero potential bus.

The drawing shows a schematic diagram of the proposed voltage divider.

The divider contains the input decade 1 of resistors, the extreme terminals of which are the input 2 of the divider; multi-switch 3, the fixed contacts of which are connected to the output resistors of the input decade of resistors, and the moving ones to the non-inverting inputs of the main 4 and additional 5 operational amplifiers, the first 6 and second 7 large-scale resistors, the first outputs, which are connected to the outputs of the main and additional operational amplifiers, accordingly, the second terminals are combined and are the output of the device 8; the third 9 and fourth 10 scale resistors, the first terminals of which are connected to the inverting inputs of the main and additional operational amplifiers, respectively, and the second terminals are combined and connected to the bus AND zero potential.

The divider works as follows.

When connecting the reference voltage or supplying the input signal to the extreme terminals of the input decade 1 of the resistors, the operational amplifiers 4 and 5, due to the effect of the scale resistors 9 and 10, create a voltage at their outputs equal to the input, i.e. operational amplifiers are repeaters of the input voltage. The input voltages of the operational amplifiers are determined from the ratios

and ... -i ..,

(D)

; .- N

ten

and lia.N (2) t, -. S 10 2

where Uo - the value of the input signal; 10 - the number of resistors - in, the input decade of resistors;

N is the number of input steps

a series of resistors of the input decade of resistors connected to the input of operational amplifier 4; Nj - the number of input steps

a series of resistors of a decade of resistors connected to the input of an operational amplifier 5.

Operational amplifiers have an infinitely large input impedance and negligible output (with a sufficiently large gain) with open feedback. Since operational amplifiers 4 and 5 work as voltage followers, their output voltages yy.l and UgwK.e are equal to the input, i.e.

. Uo

Ex.J6) (. L

.) (J

6xx .. N, j.

Since the amplifiers 4 and 5 have negligible output impedances, their output voltages do not change when the load is connected, i.e. the output voltage at the output of the divider is determined by the ratio

J.LVA 6W-5B,

S)

and.

j j j j

Pb "7

Choosing between tg and Uy the ratio of ET. lOR, taking into account (3) and (4), is obtained after conversion

abixvf iNi o.iN). (6)

The above analysis for a divider with two operational amplifiers and a multi-position switch with two moving contacts can be applied to a circuit with a multi-position switch (with p moving contacts and p operational amplifiers), while the resistance of the star resistors connected to the outputs of the operational amplifiers and bus 11 zero potential must be in a ten-fold relationship, i.e. as 1: 10: 10 ° -....

When the specified condition is fulfilled, the proposed divider with n opamps obtain the corresponding equation

Uo (, N., - tO, 01N ,, -... MO Nn

JftbW n

10 / E-77G, (

The advantages of the invention are as follows:

a) the divider uses only one ten-resistor series and additionally only one resistor for each decade, which simplifies the self-calibration of the divider;

b) the divider has a constant input and a constant output impedance; .

c) in both the senior and junior decades, the level of input and output voltages of the operational amplifiers is the same (depends only on the number of stages of a series of resistors connected to the inputs of the operational amplifiers), resulting in a reduction in the effect of the drift of zero operational amplifiers in the younger decades ; .

d) a constant output resistance allows, in a simple way, by connecting a resistance of a certain size to the output terminals, to obtain potentiometers with the desired limit of measurement;

e) the presence of galvanic connection with a zero potential width for all operational amplifiers. The divider reduces the effects of various types of interference and leakage.

Claims (2)

Invention Formula A resistor voltage divider containing an input decade of resistors; a multi-position switch whose fixed contacts are connected to the terminals of the input decade of resistors; the extreme terminals of the input decade resistors are input to a voltage divider, an op amp that is covered by a negative feedback circuit, the non-inverting input of which is connected to the first moving contact of a multi-position switch, characterized in that, in order to improve the accuracy and achieve constant input and output resistances, the first, second, third and fourth large-scale resistors and an additional amplifier covered by negative feedback, the non-inverting input of which is connected to the second movable at the contact of a multi-position switch, the first fixed contact of the multi-position switch is connected to the zero potential bus, the first terminals of the first and second scale resistors are connected to the outputs of the main and additional operational amplifiers, respectively, and the second terminals are combined and the voltage divider is and the fourth large-scale resistors are connected to the inverting inputs of the main and additional operational amplifiers, and the second terminals 1 | and are combined and connected to a zero potential bus. Sources of information taken into account in the examination of i 1. Digital electrical measuring instruments. Ed. V.M. Shl Ndina, M.,. Energy, 1972, pp. 211-222, Fig. 519. 2. USSR author's certificate No. 555407, cl. G 06 G 7/16, 1975 (prototype).