SU1601588A1 - Resistive divider of constant voltage - Google Patents

Abstract

The invention relates to electrical measuring technique and can be used in the manufacture of electrical measuring instruments, their calibration and calibration. The purpose of the invention is to increase the accuracy of voltage division and the efficiency of using the divider circuit elements. The device consists of series-connected output and four input stages, each of which consists of series-connected constant resistors and trim resistive circuits. As a result, a constant voltage dividing circuit is formed on the constant resistors 7-34 and the trim resistor circuits 16, 18, 20, 31, 33, 35, electrically connected to the contact sockets 36-65. Through these sockets, resistors 7-35 are connected by plugs 66-70 and are converted into bridge measuring circuits with a zero-organ and a power source. The introduction of additional steps of dividing the voltage, and as elements of the shoulders of the bridge during autonomous adjustment and calibration of the division factors, eliminates the use of external connecting devices, such as bridges, potentiometers, as well as measurement errors and adjustments made by external devices. 4 il.

Description

The invention relates to electrical measuring technique and can be used in the manufacture of electrical measuring instruments, their calibration and calibration, as well as for accurate measurements over a wide range of voltages.

The purpose of the invention is to increase the accuracy of voltage division and the efficiency of using the divider circuit elements.

Figure 1 shows the electrical circuit of the resistive voltage divider; 2 is a trimming resistive circuit; FIGS. 3 and 4 show bridge measuring circuits for autonomous adjustment and calibration of a voltage divider, formed from a divider circuit.

The diagrams indicate the terminals 1 - on the input and output, resistive elements 7 - 35, forming a divider and electrically connected to the contact sockets 36 - 65, through which the forcing of resistive elements 7 - 35 and their adjustment to bridge measuring circuits with zero-body 71 and power supply 72 for autonomous adjustment, calibration and operation of the divider.

The output stage between terminals 5 and 6 is made on a constant resistor 34, which is connected in series with a trimmer resistor 35, which is (Fig.2) two in series, connected sets of resistors — Coarse and Accurately, each of which each contains two constant resistors 35-1, 35-2 and 35-3, 35-4, connected in parallel with each other, and one variable

(trim) resistor 35-5, 35-6 with a series connection of one variable resistor to one constant resistor. Similar circuit construction for all trimmer resistive circuits 16,18, 20, 31 and 33, included in other levels of the voltage divider .-

Entrance steps 1 - IV limited by clips 1, 2; 2, 3; 3, 4 and 4, 5, are connected to the output stage using forks 69 and

70

The first input stage is made on

a constant resistor 32 and a successively trimming resistor 33 connected to it. The same construction of the third input stage, bounded by clips 2 and 3, which also has a constant resistor 19 and is identical to the circuit 33 of the resistive trimmer 20.

The second and fourth stages, respectively, limited by terminals 1,2 and 3,4, 5 contain a transfer from resistors 21–29 and 7–14 (by which is meant a circuit of resistors made with the possibility of its conversion from a series connection of resistors to a parallel one, and 0 vice versa), as well as constant (additional) resistors 15,17 and 30 and identical trimming resistive circuits 16, 18 and 31, connected respectively to one of the resistors 15 respectively. 17 and 30. 25 The division ratio of the voltage divider is determined by in the bridge scheme (fig.Z and 4), the shoulders of which are formed by an adjustable voltage divider and a supporting element, 30 as used; when adjusting the first two dividers, the transfer (resistors 21-29) of the second input voltage divider, and when adjusting the second two division factors, the output, first, and second voltage divider levels are sequentially adjusted. The shoulders are formed by the first and third input, divider steps and 40 chains of their constant resistor and trimming resistive circuit of the second or fourth voltage divider stage. At this, the methodical error of the shoulders of the bridge of mouth equals 45 - the bridge balance index counting with the mutual permutation of the ratio arms. The methodical error of the voltage divider is eliminated by adjusting the voltage divider stage to zero count of the bridge equilibrium gauge and adjusting the voltage divider step and the resistor circuit that forms the shoulders of the bridge ratio until a zero equilibrium pointer is readjusted when one of the ratio arms and the comparator arm are zero, formed by the transfer, with simultaneous switching of the parallel connection of the transfer resistors to the series.

 With this, the formation of the bridge scheme; its shoulders are switched and rearranged using forks, one set of forks is used, when adjusting both the first and second two factors of the voltage divider, and the working circuit of the voltage divider is formed using two identical forks. In this case, the range of adjustment of the resistance of the circuit (second or fourth voltage divider) is chosen so that the restriction arises when adjusting signals an unacceptable change in the resistance of the resistor of the supporting element, and the resistance of the low-resistance voltage divider is adjusted by means of a resistance trimmer. scheme.

The nominal resistance values of the resistors that make up the voltage divider satisfy the following equations:

R7 R8 Rg Rio Rii Ri2 Ri3 Ri4 Ri5 + Ri6 Ri7 + Ri8 Ri9 + R20 900 (Рз + RSS);

(one)

R21 R22 R23 R24 R25 R26 R27 R28 R29 R30 + R31 R32 + R33 9x (R34 + R35).

 (2)

The division factors of the voltage divider are determined from the ratios K, o R32 + R33 H - R34 + R35 RBBIXR34 + RGS

KIOOO

 RIII + RII + RI - f RBUX

out

 Rl9 + ... h - R31 + R32 - f R33 + R34 + R35 R34 + R35

1000;

(five)

ten

KlOOOO - V - + + RI - RBBIX

R

out

15

R7-b ... -f-Ras

R34 -b R35

10,000

(6)

There is a dock of autonomous adjustment and checking. The null organ 71 is connected to the input terminals 4 and 5, and the power source 72 to the terminals 3 and b, as shown in FIG. 3, includes the contact plug 66 in the sockets 51 53-55-57-59-64, 50 -52-54-56-58-60, 61 - 62, 63 - 65. It forms

a bridge circuit, the shoulders of which are formed by an adjustable voltage level 5-6 and a voltage divider and a supporting element formed by a transfer of parallel-connected resistors 21-29,

The relationship arms are formed by a first stage 4-5 and a circuit of resistors 30-31 of the second stage 3-4 voltage dividers. Counting "1 null organ 71;

;

35

"1 S (bz4.35 - (5z2.33 - 5o + (5zo, 31),

(7)

40

where S is the sensitivity of the bridge circuit; 034.35, (5з2, зз, з1 - Relative error of resistance forming the shoulders of the bridge;

Оо - relative error of the support element.

Since the adjustment and verification is carried out with respect to the supporting element,

 can be accepted (5o 0.

A new count of the zero-organ 71: d is established by changing the resistance of the arm 32, 33 of the bridge ratio (first stage of the voltage divider). In this case, from (7) is obtained

ten;

K,

RBUX

(3)

 R21 + ... + R3t R32 + R33 + R34 -b R35

R34 + R35

(four)

5z4.35 - (, sz + 5zo, 31 (5o o.

55

(eight)

100

Then the plug 67 is turned on in the slots 51-53-55-57-59-64, 50-52-54-56-58-63, 60-65, 61 - 62. At the same time, the shoulders of the bridge ratio are swapped, fig.Z (designation in brackets).

Countdown of zero-organ 71:

aa 8 (bz4.z5 + ,. з1). (9)

Adjust the other leg 30, 31 of the mbstation ratio (resistor circuit of the second stage of the voltage divider) by adjusting the variable resistors of the trimming circuit 1 so that the new zero-organ reading

oa

f.

(ten)

Then, taking into account (9) and (10)

dz4 35 + -33 -f 934.35 - 2,33

(eleven)

Substituting in (11) the expression for zo, 31 of (8):

dz435 + 33-5o + (5z4.35 - 2.33

-; 2

  , 35 + .33 - before -, 31

LI

., 33. (12)

Then, by adjusting the resistance of the shoulder 34,35 comparing the bridge (the output stage of the voltage divider), by adjusting the variables, the resistor JB of the trimming resistive circuit 35. get a new reference 02. a null organ: "2 O and then taking into account (12) from (9) we get

, 33 0. (1

Thus, the output level of the voltage divider is adjusted to the reference

element.

Then the plug 68 is inserted into the sockets 50-60, 61-64, 59-62, 63-65. This forms the bridge circuit shown in FIG. 4, where in comparison with the diagram of FIG. 3, the interlacing arm 30, 31 is mutually shifted bridge and shoulder of the comparison - support element, formed by transfer from the constant resistors 21 - 29 with simultaneous switching of the parallel connection of the transfer resistors to the series one.

The relative error of the support element after T1 parallel-sequential transformation with an accuracy of

the magnitude of the second order of smallness is equal to the relative error of the support element before conversion to, since the error of parallel-serial

conversion is equal to - ss where p i

the number of transfer resistors; SC is the deviation of the resistance of the 1st transfer resistor from the average value of the resistance. The counting body of the null organ 71:

Si S (44 ,,.). (14)

5 By adjusting the resistance of the arm 32, 33 of the bridge (the first stage of the voltage divider) with the help of variable resistors of the trimming resistive circuit 33

A new reading of the o-null organ appears: I

CQ -, then by adjusting the resistance of the bridge arm 30, 31 (the voltage circuit of the second stage of the voltage divider) using variable resistors of the trimming resistive circuit 31, the zero-organ Oz 0 is read.

After that, taking into account (12) and (13), from (14) we get

thirty

6} b ,,,, (15)

those. The output, first, and second-stage resistor group of the voltage divider are sub5 based on the supporting element (a chain of second-stage resistors). Since the relative errors of all the steps are equal, we get the finally exact expressions expressed by formulas (3) and (4)

0 for the first two division factors

Kyu and Kioo.

To form a series connection of the voltage divider stages, the plug 70 is inserted into the sockets 59, 60, 61, 5, 62 and 63, 64.

Similarly, the adjustment of the two other division factors of the Kyoooi and Kioooo voltage divider is performed by adjusting the resistance of the third and fourth steps, and the trimming output, first, and second divider stages are used as the reference element. The steps are switched by the same forks.

66-68,

55 Finally, after adjustment, we also obtain exact expressions for the division coefficients Kiooo and Kioooo by

formulas (5) and (6),

In a similar manner, a voltage divider calibration is carried out autonomously.

it is only during calibration that the adjustment of the resistances of the steps is not carried out, and only readings of the readings of the null organ 71 i, Cfe and Oz are made. Then, solving the system of equations from expressions (7), (9) and (14), finds the desired relative errors of the divider levels and the errors of the division coefficients.

To control the sensitivity of the S bridge circuit in the voltage divider stages, the percent resistances are switched on by the button in series with the step resistors (not shown). The percentage resistance introduces an additional error of 0.01% into the relative error of the voltage divider and allows an objective assessment of the sensitivity S of the circuit and the control of the latter by changing the output voltage of the power source 72.

The range of adjustment of the resistance of the second or fourth stage of the voltage divider using trimming resistive circuits is selected based on the permissible error of the voltage divider caused by adjusting the practical component of the error of the support element due to the error of parallel-serial conversion

.

eleven

(sixteen)

caused by the deviation of the resistance of each i-ro transfer resistance from the average value.

Since for deviations from the average is true

,

eleven

This is for the Kth resistor of the chain.

-E

about

 one

(17)

Replacing in (16) the deviations a by some average value a, besides the oic of the Kth resistor, we obtain the expression for the error of the series-parallel transformation:

ar,

(18)

Taking into account (17), the component error of the parallel-serial conversion from the change in the K-th resistor

Р8к

(nineteen)

ten

15

Thus, the allowable value of the error of the voltage divider due to the change in the resistance of the support element from the change in resistance of the transfer resistor determines the range of adjustment of the voltage divider levels, i.e.

-A - (n-lf -D-

but

(20)

where as a. The normalized value of the error of the transfer resistors (deviation from the nominal value) specified in the technical documentation for the resistors used is accepted.

Thus, the arising restriction during adjustment - going beyond the adjustment range - signals an unacceptable change in the resistors of the support element.

The resolution of the adjustment of low-resistance levels of voltage dividers is determined by the resolution of the trimming resistors, which is in the order of 0.5-1% of the nominal value of the resistance of the trimming resistor. Since, with a discretization adjustment of d 10, the resistance of a low-resistance stage, for example, Pout x 1 kΩ, the required total resistance of the trim resistor is 0.1 Ω with a resolution of 0.001 Ω. Practically, such resistors do not exist.

The inclusion of a trimming resistor with a series-connected DC resistor and parallel to it connected by another DC resistor forms a resistive fine-tuning circuit.

Figure 2 shows a resistive trimmer circuit 35 consisting of two fine and coarse trim circuits.

Consider the operation of the scheme on the example of fine tuning. A series resistor 35–3 is connected in series with tuning resistor 35–6 and a resistor 35–4 is connected in parallel with them. The nominal resistance values of the serial 35-3 and parallel 35-4 resistors are based on the nominal resistance value of the available trimmer.

the resistor 35-6, the discreteness of the adjustment d and the permissible nonlinearity of the adjustment in the formulas

four

 (1-4 #) R35-6

R

out

id

(21)

R35.-6

-R35

(22)

where is the non-linearity of the adjustment (in relative units);

Rebix resistance of adjustable voltage divider;

d - discreteness of resistance adjustment is necessary (in relative units);

jU is the resolution capability of the variable resistor.

Similarly, the values of the resistances of the resistors 35-1 and 35-2 of the coarse adjustment circuit and the resistance adjustment circuit of the other levels of the voltage divider are calculated.

The increase in the accuracy of the voltage divider is achieved due to the following factors.

Autonomy adjustment and verification. No errors are introduced due to the presence and variations of transient resistances of external connecting devices, which occurs when tuning other voltage dividers using external bridges, potentiometers, etc. The autonomy of the adjustment and verification makes it possible to eliminate errors that occur when adjusting the dividers using external bridges and potentiometers: by changing the measurement mode (currents and voltages) when measuring the differing impedance of the divider arms and the limited capabilities in accuracy and sensitivity of bridges and potentiometers.

Completeness settings. All the Tselitel bridge shoulder resistors) are simultaneously present at all switchings, measurements, i.e. there is a mutual adjustment. With other methods and devices implementing these methods, the shoulders of the divider are adjusted separately when disconnecting the non-adjustable arms, which contributes to the occurrence of additional errors from heating by the operating current, thermo-EMF, from short-term instability of resistors,

More complete use of the divider circuit elements occurs due to the fact that the same functional divider elements (resistors, resistive circuits) are used as elements of the divider stages.

and as elements of the shoulders of the bridge in the autonomous adjustment of the divider and verification of the division factors of the divider.

20

Claims (1)

Invention Formula A resistive DC voltage divider containing a series-connected output stage on a constant resistor, the first input a step from a chain of constant resistors, a trimming and additional resistor circuit, and a resistive measuring bridge, characterized in that, in order to increase the accuracy of voltage division and the efficiency of using the divider circuit elements in series with the first input stage includes at least three additionally entered input stages, each of which consists of series-connected fixed resistors and trimmer resistors, the trimmer resistors of the second and fourth input stages are identical to the trimmer resistors of the first and third input stages, respectively, and the whole circuit of resistors of all stages forming the divider is designed to conversion to the quadruplex resistive measuring bridge. rpgSo Figg Fi.Z