SU1337792A1 - Digital voltmeter - Google Patents

Abstract

The invention makes it possible to increase EXACTLY a measurement with a voltmeter in usvs, it contains a source 1 of a reference voltage, a scale converter 4, a switch 6-8 polarities, a pulse generator 10, an integrating analog-time converter 11, a selector 12, a computing unit 13, blocks 14 and 17 control and display and reference voltage source 15, the introduction of a source 2 of a reference voltage, a scale converter 5 and 9, and a polarity switch 16 eliminates the effect of changing the internal resistance of the signal source and eynosti transducer voltage in the time interval. F / ug /

Description

133

The invention relates to electrical measuring equipment and can be used to measure the DC voltages of high-resistance sources under the influence of interference.

The purpose of the invention is to increase the measurement accuracy by eliminating the effect of changes in internal resistance.

The signal source and the non-linear 9 are connected to the voltage converter in the time interval respectively.

FIG. 1 shows a functional diagram of the proposed voltmeter; in fig. 2 - functional block diagram.

The digital voltmeter contains the first and second sources 1 and 2 of the reference voltage, input 3, the first and second scale converters 4 and 5, the first 6, the second 7 and third 8 polarity switches, the third scale converter 9, the pulse generator 10, integrating the analog -time converter 11, selector 12, computing unit 13, control unit 14, reference voltage source 15, fourth polarity switch 16 and display unit 17.

The first moving contact of the switch 6 is connected to the first input of the converter 9, the second moving contact to the first moving contact of the switch 7, the second moving contact of which is connected to the first moving contact of the switch 16, the second moving contact of which is connected to the second input of the converter 9. Source outputs 1 connected to the inputs of the converter 4, the outputs of which are connected to the fixed contacts of the switch 7. The outputs of the source 2 are connected to the inputs of the converter 5, the outputs of which are connected to The fixed contacts of the switch 16. The outputs of the third large-scale converter 9 are connected to the first and second inputs of the converter 11, the output of which is connected to the first input of the selector 12, the second input of which is connected to the output of the generator 10, and the output to the input of block 13, whose information output connected to the input of the unit 17. The outputs of the source 15 are connected to the fixed contacts of the switch 8, the first movable contact of which is connected to the common bus, and the second

moving contact - with the third input of the converter 11.

Engraving inputs of converter 11, selector 12, computing unit 13, display block 17, first 6, second 7, third 8 and fourth 16 polarity switches, scale converters 4, 5 and

0

14

five

This is the eleventh output of the control unit, the first input of which is connected to the polarity output of the converter 11, and the second to the control output of the unit 13.

The control unit 14 (Fig. 2) contains a clock pulse generator 18, the output of which is connected to the first input of the element 19, the second input of which is connected to the second input of the block 14, and the output to the counting input of the pulse counter 20, the outputs of which are connected with inputs of a persistent storage device 21, the first - the seventh outputs of which are connected to the fifth, sixth, eighth, second, third, fourth outputs of block 14. A delay element 22 is connected between the output of the generator 18 and the first output of the block 14. Pulse former 23 included first in Odom unit 14 and the seventh output unit 14. The input of the 24, 25 and 26 are connected to the second pulse input unit 14, and outputs - a ninth, tenth and eleventh output unit 14, respectively.

Digital voltmeter works as follows.

According to the signal of the control unit 14, the transmission coefficients of the large-scale converters 4 and 5 are set to be minimal, at which the reference voltage is 0.

five

0

jump on their output u,

five

0

will be minimal, where K. .- transfer coefficients mas01

Wow.

TO,; .

staff converters 4, 5-, E

Egj are the output voltages of the first 1 and second 2 sources of the reference voltage, respectively. When this switch 6, 7 and 8 polarity is included in the position when the input of the large-scale converter 9 receives a voltage

(.). Ri

RX og

 what?

Uc, + and „. ),

where E is the measured voltage;

R is the internal resistance of the measured voltage source connected to the input 3 of the voltmeter internal resistances of the converters D and 5 with respect to the fixed contacts of the IQ switches 7 and 8;

R is the input impedance of the converter 9,

,, ,,. U. -

 a, short. .

K, R

01

where uj.

02

 i5AlEoi K L + Eo2 K,) Rv

R.,

 o (E, -K ,,. E „,,, E„,) - d (E and „, + Uo,),

oii 02 E (, K21.

(V

Rn

15

R + RO, -bRci + R.

In the process of carrying out the above operations, it is possible to choose the values of the e alon measures U, and U., which are commensurate with the value of the measured capacitor E of the value E.

The measurement cycle consists of six

cycles. In the first cycle switch- input integrating analog-time-on l -, g,

 . o, 7 and polarity

A voltage of approximately 1/4 is supplied to converter 11.

working range. This is determined by

At the input of the converter 11, the post-scale converter 9 is switched to a position where

to the position in which the sources E, and, and (J2 j are included according to.

and ,, according to the code received at the output of the selector 12:23

N, a „+ a, Cs, o; u, -fa, K2. .. ziz,

where ay, a, a, a - the coefficients of the transfer function. 20

The choice of the value of the coefficient is where K., Rj. reducing K, the scale converter 9 changes the value of N to obtain the ratio N 4 Nycr, where the code value is 1/4 of the conversion range N of the converter 11, the selector 12 and the generator 10 of pulses; N is the code value at the output of the selector 12 at the maximum allowable voltage value at the input of the converter 1 1.

After that, a change is made.

the values of the coefficient K. the conversion of the scale converter 4

to obtain the value of the reference From here, the voltage U ,,,. ,;, resulting in a code for the number 2N: U ,,.

stresses

(E ,,., - bn, j (b-5Oil

02 i

R + R

,, .. + R .. + R ,. -l-5- -

02

R ,, + RV

35

-equivalent parameters of the converter 9, represented as a voltage divider with resistances R. and. Il.-,

- input impedance converter 11}

40

Vi

R. ,, + Ro2 R2; - v

O / CE, -t-Uo ,, - t-Uoj ,.),

N, 2N ,, K ,, rfU ,. .U, +

+ a, short circuit ,. .3 of

where and

(ExiKj,) Rv

,

 "C (E, -hK ,.

+ and „) (E, + U,. ,,).

After that, the coefficient K of converter 5 is changed to obtain an increment of the code NJ by the value 2N.J:

,, ,,. U. -

 a, short. .

Uj.

 i5AlEoi K L + Eo2 K,) Rv

R.,

 o (E, -K ,,. E „,,, E„,) - d (E and „, + Uo,),

oii 02 E (, K21.

15

 „

to the position in which the sources E, and, and (J2 j are included according to.

and ,, stress

(E ,,., - bn, j (b-5Oil

02 i

R + R

,, .. + R .. + R ,. -l-5- -

02

R ,, + RV

K., Rj.

-equivalent parameters of the converter 9, represented as a voltage divider with resistances R. and. Il.-,

- input impedance converter 11}

where K., Rj.

Vi

R. ,, + Ro2 R2; - v

O / CE, -t-Uo ,, - t-Uoj ,.),

In the second measurement cycle, the switches 6, 7 and 8 of the polarity are switched to the opposite state, at which a voltage is applied to the input of the converter 11

55

Ui,

- o / (E, and „, and ,,,).

In the third cycle compared to the first cycle, the switch is switched to the opposite state.

51337792

At the same time, the input of the converter 1 1 in each of the measurement cycles by means of the polarity switch 16 - the control unit 14 supplies the input of the converter 11 with the voltage U, the source 15 of the required polarity. In the fourth cycle switches

6, 7 and 8 are transformed in the opposite way. The function of the transformed state in comparison with states 11 is described by a polynomial view in the third cycle. Input is dominated by voltage

and ,, - o (E, + Uo ,, - Uo7) 10

Developer 11 receives voltage and. . - (Е, ,,, - and „/).

ten

t a +.

Therefore, after transformations U ,,. , Uji, and, -,, and. Uj. , g, we will get the system. In the last measurement cycle, the switch is taken from the topic of readings: telephones 6. 7 and 8 polarities are translated

to the position at which the input is pre- N f t, f (,, UJ.); educator 11 stresses

N, f ,, (a, + a, U, + a ,. -f); 5, - - (Е, - and ,,. + And „,).

(a, + a, of; aaa, + a, of,); In the sixth cycle switches 6, 7

and 8 is transferred to the position at which - (, U + a ,, U. +3.11 tori) voltage 25 is applied to the input of converter 11

and ,, --- (Е, -и „,, ,, and„ ,,)

Depending on the polarity of the voltage and. Uj; , U}, -,, Uj,, Ue,.

EX

., UNi + N J z (N3.lN4)

 UO, JCN, + N) - (NJ + N,) J - u ,; (n, + s,) - You 5 + s,) f

Based on known Up values. Ugjj the definition of E "is performed in the computing unit 13

Block 14. control works as follows.

In the process of selecting the values of the reference stresses U; ,,, - and. the signal from the output of block 13 closes the element 19 and sets the different transmission coefficients K, - and Kj, scale converters 4, 5 and 9. For this, shapers 24, 25 and 26 are introduced, which serve to communicate the digital and analog parts of the voltmeter. Shaper 23 is inserted to control the position of the polarity switch 16. At selected values of the reference voltages U and Upj commensurate with E,, the input signal of the element And 19 receives a signal that opens this element. Therefore, the first next pulse from the output of the generator 18 translates the counter 20 into a single state. The code at the output of the counter 20 controls the operation of the constant for the Conversion Function Conversion 11 is described by a polynomial

ten

t a +.

N, f ot, f, (a, + a, U, .. a.U);

Since U, .- U ,. ; .-l, -; get dependency

a reminder device 21 in which the necessary combinations of states of the switches 6, 7 and 8 and the control signals of the selector 12 are stored, in blocks 13 and 17. With some delay

from the output of the element 22 of the delay at the input of the start of the Converter 11 receives the pulse Start. At the end of six measurement cycles in the seventh cycle, the signal 13 of the block 13 receives the Processing signal, the value of the measured value is determined and the signal is sent to the block 17 of the display.

Thus, the proposed digital voltmeter allows to increase

accuracy of voltage measurements when the internal resistance of the voltage source varies in a wide range of values and when there are third order coefficients in the function

Claims (1)

converting a voltage converter into a time interval. DETAILED DESCRIPTION OF THE INVENTION time converter, selector, transmitter and display unit, the control inputs of which are respectively connected to the first, second, third and fourth outputs of the control unit, the output of the pulse generator is connected to the second input of the selector, the first polarity switch, the fixed contacts of which are connected to the device inputs, the input control unit is connected to the fifth output of the control unit, the second movable contact is connected with the first movable contact of the second polarity switch, the control input of which is connected to The normal output of the control unit, the seventh output of which is connected to the control input of the third polarity switch, the first moving contact of which is connected to the common bus, the second moving contact to the input of the analog time converter, and the fixed contacts are connected to the outputs of the voltage source, and a first reference voltage source, characterized in that, in order to improve measurement accuracy, a second reference voltage source, first, second and third scale converters and even polarity switch, the control input of which is connected to 0 five the eighth output of the control unit, the first movable contact with the second movable contact of the second polarity switch, the fixed contacts are connected to the outputs of the second scaler, and the second movable contact is connected to the second input of the third scaler, the first input of which is connected to the first movable contact of the first switch field and outputs are connected to the first and second inputs of the analog-time converter, the polarity output of which is connected to the first input of the control unit The outputs of the second reference voltage source are connected to the inputs of the second scale converter, and the outputs of the first reference voltage source are connected to the inputs of the first scale converter, the outputs of which are connected to the fixed contacts of the second polarity switch, and the control outputs of the first and second and the third scale converters are connected respectively to the ninth, tenth and eleventh outputs of the control unit, the second input of the controller is connected to the control output in the computing unit. 0 0 FIG. 2