SU1404962A1 - A.c. microvoltmeter - Google Patents

Abstract

The invention can be used to measure the effectiveness of stresses. An AC microvoltmeter contains transducers (P) 3, 5, summing and subtracting 2 blocks, square-addressing detectors (CD) 7, 9, 12, 13, adder 10, integrating amplifier 11, large-scale P 4, amplifiers 6, 8, link 14 feedback. In this case, the transmission coefficients of the amplifiers 6, 8 and CD 7, 9 are related by the relation. , K 90, where K, 70 80 90 the transmission coefficients of amplifier 6, CD 7, amplifier 8 and CD 9, respectively, and the transfer coefficients of P 3, 5, scale 4, and 4 and amplifiers 6, 8 are related by (Кзо + К Кдо) К / л- (к, ..- Ксо К.К, 40 VJ 60 - 30 "4о fiO 50 40 coefficients ne50 where Kjo, K redacci P 3, 5 and large-scale P 4, respectively. 1 cf f-crystals , 1 Ill. S

Description

sixteen

ABOUT

four; o o)

The invention relates to the field of electrical measurements and can be used to measure effective stresses.

The purpose of the invention is to increase the accuracy by generating signals of the same level on the square detectors of the multiplication channels and inversely transform the output signal.

The drawing shows a structural diagram of a microvoltmeter.

The AC microvoltmeter contains a summing unit 1 and a subtracting unit 2, the first converter 3 whose output is connected to the first inputs of summing 1 and subtracting 2 blocks, a large-scale converter 4, the output of which is connected to the second inputs of summing 1 and subtracting 2 blocks, and the input is connected with the output of the second Converter 5. The output of the summing unit 1 through the first amplifier 6 is connected to the input of the first square detector 7. The output of the reading unit 2 through the second amplifier 8 is connected to the input of the second square guide detector 9. The output of the detector 7 is connected with the straight, and the output of the detector 9 with an inverted input of an adder 10. The output of which is connected to an integrating amplifier 11, whose output is connected inputs of the third 12 and fourth 13 kvadratiruyu- ischh detectors. The output of the third detector 12 is connected to an additional direct, and the output of the fourth detector 13 with an additional inverse input of the summator 10. Between the output of the integrating amplifier 11 and the inputs of the detectors 12 and 13, if necessary, change the feedback transmission circuit, link

14 feedback. The output of the amplifier 11 is also connected to the readout unit.

15 (a switch or digital device), Inputs of converters 3 and 5 are connected to the input terminal 16.

Variable voltage amplifiers can be used as converters 3 and 5 50.

The transmit factors of amplifiers 6 and 8 and detectors 7 and 9 are related by the ratio

2 1 KfeO 70 K 80 90

 (, 0 g transfer ratios

amplifiers 6 and 8; 70 90 transfer ratios

detectors 7 and 9.

The transfer coefficients of converters 3 and 5, scale converter 4, and devices 6 and B are related to each other by the ratio,

(, „.

к.о) к, „(к -к

40

Eo

50

K, o) K

8o

five

0

five

0

0

five

0

five

five

where Kj (,, - transfer coefficients

converters 3 and 5; K4o transfer ratio

scale converter 4.

Microvoltmeter AC operates as follows.

The input AC voltage U (t) is amplified by converter 3 and fed to the first input of summing unit 1, the second input of which also receives voltage Ux (t), amplified by converter 5 and converted by scale converter 4. Similarly, this voltage goes to both inputs of the subtracting unit 2, The voltages from the outputs of the summing 1 and imitating 2 units are additionally amplified, for example, by the power of the amplifiers 6 and 8. These voltages are then detected with the first 7 and second 9 detectors. The output voltages of these detectors are subtracted in the adder 10. The output voltages of the detectors 12 and 13 are also subtracted in the adder 10, and the resulting differences in the output signals of the detectors are subtracted, i.e. there is a relationship

(and, - Ug) - () whether (1)

The resulting uncompensated voltage at the output of the adder 10 is amplified and integrated using an integrating amplifier 11, and then measured by a reading unit 15. Through a feedback link 14 or directly the output voltage of the amplifier 11 is fed to the inputs of the detectors 12 and 13. For high-quality microvoltmeter operation conversion factors (gain, attenuation) of blocks 1-6 and 8 are chosen such that detectors 7 and 9 have the same level of input voltages

(and, - and „) and, -

(2)

Transmission coefficient of each unit

k, k „, (1 J,) (3)

For high-quality microvoltmeter operation, you must perform the necessary settings.

Condition

To „„ (4)

25

n ,. n, - to,

60 70, 0 90

necessary to suppress the quadratic terms in expression (2).

Condition

) - K, (K, -K

(Кзо + К с

K.o) K, / 5)

Cho 60 SO is necessary to provide the same voltage levels at the inputs of the detectors 7 and 9.

For practical implementation, except

Moreover, it is convenient to choose so that Kjp K

TO

No

TO,

TO

10- Mo 50 If we consider a win-win Y. 0.5 (voltage divider), then from conditions (4) and (5) receive

(6)

to oh

7о 90 5

K, 40 9 k, 50

taking into account expressions (3) - (6), the extrusion of (2) after transformations and, neglecting the product of errors, takes the form

 К, о Кз о 2 + 3.25, -2.25;, - 0,

0, 2uz-l

2t

TO

K, s

3 (2P 2

7

 to,

7o (2h, + - 23 ,,) U, Kyi + 2j.).

x (9 + y, - 1 -,). From where taking into account

and 11 UB get 35

J

j

YU

15

20

25

thirty

35

40

Detectors 6 and 8, detectors 7 and 9, and may be very small (make up hundredth fractions of a percent). I i

All detectors operate at the same voltage levels and their effect on the resulting microvoltmeter error is also determined by their nonidentity. This non-identity is (0.05-0.1)%.

The microvoltmeter has a linear character of the dependence of its output readings on the rms value of the measured voltage, and it can be implemented with both analog and digital readouts.

Claims (2)

1. A microvoltmeter of alternating current containing the first and second generators, the inputs of which are connected to the input terminal, the summing and subtracting blocks, the first inputs of which are combined with each other and the output of the first converter, the second inputs are combined with each other, the first and second square detectors, the output of the first one is connected to the direct one, and the output of the second one is connected to the inverse input from the GMmator, the output of which is connected to the output of the integrating amplifier, the output of which is connected to the output terminal, characterized in that Accelerating accuracy, it is further introduced scale converter, the first and second amplifiers, the third and fourth kvadratiruyuschie detectors, an adder configured to further direct and inverted inputs, the scale converter input connected to the output vtorogo.preobrazova Where or ib ,, 5Kzo K ,, Uk7o 1 - - (-.- y) d, + 0.25i ;; 5g a-p; - inputs LTt Tfb ifi summing and subtracting blocks,  the output of the summing unit through the first amplifier is connected to the input of the first square detector, the output of the subtracting unit through the second 50, the amplifier is connected to the input of the second square detector, the output of the integrating amplifier is connected to the inputs of the third and fourth detector, the output of the third square detector is connected to an additional direct module. 1, .13 -TB T3-: yii) + T63 fe j 16 Ivi Gtgz (8) From the analysis of expressions (7), (8) it follows that in this microvoltmeter the additive error caused by the noise of converters 3 and 5 is sharply suppressed and depends only on the difference of multiplicative errors to the additional direct, and the output of the fourth square detector to the additional inverse input adder, in addition. a quad detector for a sub-direct. It also leads to an additional direct, and the output of the fourth square detector to an additional inverse input of the adder, in addition. the transmission coefficients of the first and the left amplifiers and the coefficients of the first and second quadratic detectors giving are related to TO,. to: .- K, K5 „K ,. TO where is kj TO CHO 70 -Tool amplifier transfer ratio; - transfer coefficient of the second square vector; -the transmission ratio of the booster amplifier; -the transfer coefficient of the square-square vector, and the transfer coefficients of the first second converters, scale 70 90 TO thirty the first and second amplifiers are connected by the ratio () К4о (Кзо-К 5t) 4o) -Kjo where Kjo is the transmission coefficient of the first converter; transfer coefficient of the large-scale converter; transmission coefficient of the second converter. I. 2. A microvoltmeter in accordance with claim 1, wherein the output of the integrating amplifier is connected to the inputs of the third and fourth quadrature detectors via a feedback link.