SU1427306A1 - Voltage calibrating resistance box - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to increase accuracy. The device contains voltage followers (PN) 1 and 2, a measure of 3 ratios, a controlled multiresistor 4, a voltage source 5, switches 6 and 7 performed on the keys, and output buses 8, 9 and 10. When using devices As a resistance store, the voltage at its terminals depends on the current source current connected to buses 8 and 10, as well as connected depending on the playback range of the resistance of one of the resistors of the controlled multiresistor 4 and does not depend on the transient resistance of the switches of switches 6 and 7. Such n The connection of resistors completely eliminates the effect of transient resistances of the keys, which ensures high metrological x-ki devices. When using the device as a voltage calibrator, the voltage on tires 9 and 10 is determined by the voltage value of source 5 connected by switches 6 and 7 to outputs 1 and 2, and the code recorded in measure 3, ti does not depend from residual key parameters. The output impedance of the voltage calibrator is determined by the output impedance of the PN 2. 1 11l. sl And to M with about 05 fO

Description

 U

The invention relates to a measurement technique and can be used for the manufacture of resistance stores — voltage calibrators, for example, in the manufacture of instruments for testing thermal engineering measuring instruments, which work with resistance thermal converters, and with thermoelectric converters (thermocouples).

The purpose of the invention is to improve the accuracy,

The drawing shows the structural electrical circuit of the proposed device.

The device contains the first and second voltage followers 1 and 2, the ratio 3 measure, the controlled multiresistor 4, the voltage source 5, the first switch 6, made on the n keys 6, 6, 6, the second

7

chh 71 s, 7, ... .7 9. and 10

The device works as follows.

When using the device as a resistance magazine, the outputs of the device are the output buses 8 and 10, and when using the device as a voltage calibrator, use the output tires 9 and 10.

Consider the operation of the device in each of these modes.

p f

weekend tires 8,

When using the device as a resistance box, one of the resistors of the controlled multiresistor A (depending on the reproduction range of the resistance) using the first and second switches 6 and 7 is connected respectively to the outputs of the first and second repeats of voltage 1 and 2. In this case, for example, j can be neglected.

Taking into account that the current for modern users is per, and the value is about 100 ohms (for the copiers on the field components

Then put the extension in the form:

The voltage appearing on the connected resistor of the controlled multiresistor D, using the first voltage follower 1, is reproduced at the inputs of measure 3 ratio. The input voltage at the output of measure 3 ratio using the second voltage follower 2 is reproduced between its output and output bus 10, the pita circuit and voltage repeater are galvanically isolated. When the current source is connected to the output buses 10 and 8, the voltage that occurs between them is determined by the expression

0

five

0

“;

where and.

- and

you. 2

(one)

and

voltage on vig,; 1 ng. tires 8 and 10 at prot (. current of (current source

equivalent soprot1. key acquisition of the second co-switch 7;

the voltage between the output of the second follower 2 voltage and the output bus 10.

The voltage replicates the voltage between the output and the inverting input of the second voltage follower 2, which is defined by the expression

bych.g

and

bull. 7

 : 1inhG, l (1 - /), (2)

Q

five

Where

equivalent key resistance of the first switch 6

p is the division ratio of measure 3 ratios between the common power point of the voltage follower and the output; - input current of the first repeater 1 voltage. Substituting the value of Ug ,, from expression (2) into (1), we get

and

R;

 1 „R ,,. m - I

about; P /

f,

(3)

Considering that the value of the current Igx for modern operational amplifiers is tens of pico mpere, and the value of resistance G; in the order of 100 ohms (for key elements in field-effect transistors), the component in the voltage is (3)

can be neglected.

Then the reduction (3) can be represented in the form:

loR,

S /

(four)

As can be seen from the voltage (4), the voltage at the terminals of the resistance box depends only on the current source current, the connected resistor of the controlled multiresistor 4 and does not depend on the transient resistance of the keys. The indicated connection of resistors of the controlled multiresistor 4 in the resistance shop completely eliminates the influence of the transient resistances of the keys, which ensures the dust-resistance of the latter.

When using the device as a voltage calibrator, a voltage source 5 is connected to the outputs of the voltage followers 1 and 2 of the voltage using switches 6 and 7. Similarly to the voltage described above, the output tires 9 and 10 are defined by the expression

27306

The properties are determined only by the voltage value of the voltage source 5, also by the code recorded in r-iepe 3 versus f. and does not depend on the residual parameters of the keys. The output impedance of the voltage calibrator is determined by the output impedance of the second repeater 2 voltage. Q For convenience, the code, given in relation to 3 ratios, can be additionally inverted, then expression (8) can be written as

 and

bblV.l

-

(five)

where is the weekend voltage

tires 9 and 10; vk h epr between the exit

the second repeater 2 voltage and output bus 10; 1 „- calibrator load current

- tensions; - key resistance

the second one to the fmuatatopa 7. The absolute value of Ug is determined by the expression

ay ... E, (1- (t) Tzg,., (6

ex

where Rg is the input impedance of the first repeater 1 voltage;

1 - input current of the first repeater 1 voltage; G; , R | - key resistance of the first and second switches 6 and 7; p - the value of the code set

Considering that the value of RgJ for voltage followers performed on modern op amps is relatively large (on the order of ten mega-ohms), and the current value is small, the corresponding components of expression (6) can be neglected. Then the expression (6) can be written

and

vy, 7

E / 1 - | U) +. (7)

Substituting the value of U g from the expression (7) in (5), we get

and

8th E, (1 -) + 1 „g, - 1, g ,. E, (1- |, j). (eight)

As can be seen from expression (8), the voltage of the output tires is 9 and 10 mouths.

and

15S

 E,

|| And

(9)

Claims (1)

Invention Formula Resistive - voltage calibrator J containing the first voltage follower, voltage source, first switch, characterized by the fact that, in order to improve accuracy, the second voltage repeater, the second switch, the ratio measure, the control factor, is introduced into it , wherein the first and second voltage followers are made on op-amps with artificial average point koi, and the input is controlled by multiQ with five 0 five the resistor is connected to the inverting input of the first voltage follower and is the first output of the resistor, the ratio measure is connected between the non-inverting input and the output of the first voltage repeater, the tap of which is connected to the inverting input of the second voltage repeater, the non-inverting input of which is the second the output of the resistance store and the voltage calibrate. The first and second switches are made on p-keys, with the p-1 outputs of the controlled multi-resistor connected to the n-1 inputs of the first and the second switches, respectively, the pth inputs of the first and second switches are combined and are the first output of the voltage calibrator and are connected via a voltage source to the inverting input of the first voltage follower, the outputs of the first switch are combined and connected to the output of the first voltage follower, and the outputs of the second switch are combined and connected to the output of the second voltage repeater.