SU1649571A1 - Code-controlled impedance unit - Google Patents

Abstract

The invention relates to computing and information technology, and can be used, in particular, in digital electric bridges of direct and alternating current and code-controlled measures of electrical resistance, inductance, capacitance. The aim of the invention is to expand the scope. The coding impedance block contains analog outputs 1 and 2, multiplies digital-to-analog converter 3, operational amplifiers 4 and 5, linear passive two-terminal 6, 8 and 10, scaling resistors 7 and 9. The goal is achieved by introducing linear passive two-terminal with appropriate connections, providing the formation of the active or reactive component of the block impedance and the linear dependence of the block impedance on the control code. 1 il. § (I'm with

Description

The invention relates to computational and information-measuring equipment and can be used, in particular, in digital electric bridges of direct and alternating current, in code-controlled measures of electrical resistance, inductance, capacitance,

The purpose of the invention is to expand the scope of the block.

Pa the drawing shows a block diagram of code-controlled impedance,

The coding impedance unit t contains analog outputs 1 and 29 of a multiplex digital-to-analog converter (DAC) 3, operational amplifiers 4 and 5, the first linear controller two-port 6, the scaling resistor 7, the second linear passive two-terminal 8, the scaling resistor 9 and the third linear passive two-pole 10.

As converter 3, a standard resistive matrix of the type R-2R with a kodoopr can be used as a switch containing a matched feedback resistor.

.Twopoles 6, 8 and 10 can be resistive, inductive or capacitive.

We consider the operation of the block in detail for the case of simulation of active resistances. In this case, the two-port 6 is made in the form of a resistor R. matched in resistance with the resistors of the matrix of the converter 3, the two-port 8 and 10 are also made in the form of resistors.

The transfer ratio of the transducer 3 is K Q / 2N, where 0 is the numeric equivalent of the input digital binary code; N is the converter resolution. A non-binary converter can also be used in the block, in which case the denominator will have another value8 corresponding to the maximum numerical value of the input code.

Suppose that the analog outputs 1 and 2 are applied to the voltage Ugys and plus is applied to the output 1, currents 1 and I. flow through the resistors 8 and 10; conditionally choose a positive direction of currents from pin 1.

Accepting the idealized model of amplifiers 4 and 5, i.e. believed that the potential difference between the inputs

th ,,

1649571

the amplifiers is zero, and the gain and input impedance of the amplifiers tend to infinity, we write four obvious equalities:

R

ten

U,

and

0

s

five

Q

0

 THB (U & X -) / R8 + (UBX - U4) / RW

(four)

where Rg is the equivalent resistance - the block is wait for analog water

 input current and voltage; Ug-j is the voltage at the outputs of amplifiers 5 and 4; T RIO Resistors

7 10.

Note that, under the specified conditions, a positive potential is set at the output of amplifier 5, and a negative potential at the output of amplifier 4 relative to the common bus of the unit.

After mathematical transformations, you can get a general expression for equivalent resistance

ke i / l / Rto- R7 / R8 R9 + 1 +

5 + Rr / R) / K-RIC. (5)

As can be seen from expression (5), subject to the condition of the block, it is possible to reproduce a purely active resistance linearly dependent on

about code:

R.5 R10 (1 + Rr / R9) -K. (6)

When using capacitance C, - or inductance L / as a two-way

5 lusniki 6 we will receive, respectively, a unit of code-controlled capacitance or inductance,

As a two-terminal 8 and 10-can be used capacitors or inductors. Expression

for an equivalent impedance, Z9 in this case is obtained from formulas (5) or (6) by replacing the values of Rg and R, 0 with the corresponding values of 2d and Z (0,

Thus, the proposed unit 9 ensures the formation of both the active and reactive components of the block impedance, as well as the linear dependence of the block impedance on the control code, which allows extending its area of application with

Claims (1)

Invention Formula A coding control impedance unit containing a multiplying digital-to-analog converter, whose digital input is the control input of the unit, an analog input connected to the output of the first operational amplifier, and the output to the inverting input of the second operational amplifier connected to the zero potential bus with the non-inverting input of the first potential amplifier. output of the first scaling resistor to the first analog output of the block, and output to the first output of the second scaling resistor, the second output of which is connected to the non- and the inverting input of the first operational amplifier, which is also distinguished by the fact that, in order to expand the field of application of the unit, three linear passive two-port circuits are inserted in it, the first of which is connected to the inverting input of the second operational amplifier by the first output and the second operational amplifier and the first output of the second linear passive two-terminal connected to the second output of the second analog output of the unit, the inverting input of the first operational amplifier and the first output of three another linear passive two-pole device, the second output of which is connected to the output of the first operational amplifier connected with a non-inverting input to the second output of the first scaling resistor,