SU762160A1 - Voltage to conductivity converter - Google Patents

Description

621.317.73 (088.8)

(72) Author

inventions V.N. Fedoseev

(71) Applicant All-Union Scientific Research and Testing Institute of Medical Equipment

(54) CONVERTER "VOLTAGE — CONDUCTIVITY"

The invention relates to measuring equipment, radio engineering, automation and computing, can be used in measuring devices, amplifiers with a controlled transmission coefficient, functional converters.

Known converters "voltage - conductivity", containing an amplifier, integrator [1].

The disadvantage of the known converters is the instability of the transmission coefficient "voltage - conductivity".

A voltage-to-conductance converter is also known, which contains a digital controlled conductance and an analog-to-digital converter that includes a comparator, a sign circuit, a reversible counter, a clock generator, and a digital-to-analog converter [2].

The disadvantage of the known voltage-to-conductor is the presence of quantization error due to the intermediate conversion into a digital code. This limits the accuracy and minimum acceptable voltage control signal level.

The aim of the invention is to simplify

and elimination of discreteness at

management.

This goal is achieved by the fact that the voltage-to-conductance converter, which contains a summing amplifier, an integrator, a digital-to-analog converter and a coding block, has introduced digital controlled conductivity, and the coding block is made in the form of two comparators, two voltage sources, reversible pulse counter and clock generator Yu, the comparators are connected by one input to the integrator output and the other input to the corresponding reference voltage source, the outputs are comparator 15 are connected to the direct and reverse counting buses of the reverse pulse counter, the counting input of which is connected to the clock generator

pulses.

The drawing shows a structural diagram of a voltage-to-conductance converter.

Converter "voltage - conductivity" consists of controlled conductivity 1, analog-to-digital converter 25 2, which includes a summing amplifier 3, the output of which through the integrator 4 is connected to the block 5 characters. The outputs of block 5 are connected to the inputs of the resolution enable of the reversible counter 6, the counting input 30 of which is connected to the output of the generator 7

762160

3

clock pulses. The output of each discharge of the counter 6 is connected to the corresponding inputs of the digital controlled conductivity 1 and the digital-to-analog converter 8, the output of which is connected to one of the inputs of the summing amplifier. 3, 9, 10 - comparators, 11 - code block.

Consider the operation of the device.

The control voltage signal E _y is subtracted from the signal at the output of the converter 8 using summing amplifier 3. The unbalance signal is integrated in integrator 4 and is fed to circuit 5, which controls the operating mode of the counter. The voltage-to-conductance conversion time should be insignificant for a given maximum rate of change of the control voltage. Therefore, we can assume that _y - constE. In this case, the signal at the output of the integrator And (7) varies linearly.

At that moment, when it reaches the response threshold Ει or E ₂ block 5, the counter 6 signal is sent to enable the account, and it changes its state so that the polarity of the imbalance at the output of the comparator 3 becomes opposite.

The signal and (/) reaches the thresholds £. and Εζ periodically at intervals of B and < ₂ . As a result, a code is set on the counter 6 corresponding to the input signal level with an accuracy of a quantum, and frequency-latitude pulse modulation of conductivity 1 is carried out within a quantum. The average value of this conductivity is proportional to the fill factor of the pulses at the integrator input

WITH .

γ = ——, which is proportional to its 6 + (g

queue control voltage P _y .

The values of L and / _{2 are} respectively

where τ is the integration constant;

7А ?, and 7 / d „.. _l —signals at the output of the converter 8, corresponding to the code on the counter equal to n

and l + 1;

and _Kp ^ and _y ^ and _Kn . _r1 - e = e _x + p ₂ ,

where from within the quantum the conductivity varies according to the law;

where § - low-order conductance in digital controlled conductivity 1.

four

The clock repetition frequency / _{t of the} generator 7 is selected based on the maximum rate of change of the control signal 1! _y and maximum modulation frequency

In this case there should be an inequality: L "/ 'max ·

The proposed combination of digital and frequency-width-width pulse conductivity control combines the simplicity of the circuit design of a pulse-frequency-width modulator with the accuracy of a digital conversion method. The resulting conversion error is the product of the errors in case of using the specified types of control separately. The advantage of the proposed converter is also the ability to control the gain of the amplitude-modulated High-frequency signal with further demodulation using a peak detector, since the signal is modulated as a result of pulse modulation only within one quantum n can be easily filtered.

Claims (1)

Claim A voltage-to-conductance converter containing a summing amplifier, an integrator, a digital-to-analog converter, and a coding block, characterized in that, in order to simplify and eliminate the discrete error in control, digital controlled conductivity is introduced into it, and the coding block is designed as two comparators, two sources: reference voltage, reversible pulse counter; and a clock pulse generator, the comparators being connected by one input to the integrator output and the other input to the corresponding reference voltage source, the outputs of the comparators are connected to the forward and backward buses of the reversible pulse counter, the counting input of which is connected to the clock generator.