SU711675A1 - Digital-analogue converter - Google Patents

Description

one

The invention relates to a technique for converting digital codes to analog in a sweep generator for controlling a source of vibration seismic sigals with predetermined characteristics and to be used in automatic control systems.

A digital-to-analog converter C is known, containing a set of weighting resistors connected to a diode switch, a summed-up operational DC amplifier, a reference voltage source, a thermal compensation unit in the form of a chain of series-connected diodes, one of which is connected to a common circuit and the other through a current-setting resistor with a source of reference voltage and through resistors with points of connection of weight resistors with key diodes. A disadvantage of the converter 1 is the low conversion accuracy.

The closest technical solution to the invention is a digital-to-analog converter 2 containing a decoding matrix, an increment register, elements I.

pulse generator and pulse distributor, reversible counter, sign trigger and frequency divider. The disadvantage of the transducer is its narrow functional ability to control the source of seismic signals of vibrational action with predetermined characteristics. The aim of the invention is to extend the functionality when managing a source of seismic signals of vibration action with predetermined characteristics.

The goal is achieved by the fact that a digital-to-analog converter containing a reversible counter, the first outputs of which are connected to the inputs of a decoding matrix, a frequency divider and a sign trigger, additionally introduces a reference voltage source, a converter, first and second voltage dividers, polarity reverse trigger , the output unit and the delay unit, moreover, the output of the reference voltage source is connected to the first input of the second divider and to the first input of the converter,

the second inputs of which are connected to the second outputs of the reversible counter, and the output connected to the first input of the first voltage divider, the second inputs of which are connected to the first outputs of the decoding matrix, the second outputs of which are connected to the second inputs of the second voltage divider, and the outputs of the first and second dividers voltage connected respectively with the first and second | th input of the output unit, the output of which is connected to the input of the delay unit, and its third input is connected to the output of the reverse polarity trigger, the input of which is connected to the first output of the sign trigger, the second output of which is connected to the first input of the reversible counter, and its input is connected to the first the input of the frequency divider, the second outputs of which are connected to the second inputs of the reversible counter.

FIG. 1 shows a block diagram of a digital-to-analog converter containing a source of reference voltage 1, frequency divider 2, reversible counter 3, converter 4, first and second voltage dividers 5 and 6, decoding matrix 7, sign trigger 8, reverse polarity trigger 9, output block 10, delay block 11.

FIG. Figure 2 shows the sine function in the area from 0 to 90 °, divided into 32 levels, which allows forming a signal with sufficient accuracy corresponding to a sinusoidal harmonic signal. The quantization step is 2 ° 49

The device works as follows

As can be seen from FIG. 2 sinusoid per 1/4 period can be divided into 8 sections. The slope of the sine is the cosine and the steepness of the approximation segments is different at each site, on I and 11 it can be considered constant and maximum, then its value constantly decreases and at the VIM site it is minimal.

To obtain discrete values of the piecewise linear approximation, a converter 4 is used. Consisting of transistor switches using pnpr, npp bipolar planar transistors and an R-2R resistor matrix, the reference voltage is taken from a highly stabilized source 1 reference voltage. Thus, transducer 4 can be considered as a generator of quasi-saw voltage. This voltage is applied to a voltage divider 5, which serves to change the critical section of the piecewise linear i approximation plots in accordance with the actual values of the sine. The steepness values are transmission coefficients. Voltage divider 6 provides the true value of the sine and serves to dock

UCHLGGKOV piecewise linear approximation of a sinusoid between them. In the output block 10, the stresses coming from voltage dividers 5 and 6 are added together. The decoding matrix 7 must ensure that the voltage dividers 5 and 6 are switched so that from the output of divider 5 the quasi-saw voltage is removed according to piecewise linear approximation, and from divider 6 desired levels of constant voltage, corresponding to the values of sine (Fig. 2). The decoding matrix 7 is constructed on the basis of a piecewise linear approximation and the states of the reversible counter 3.

The control pulses through frequency divider 2 arrive at the reversible counter 3, when the first 31 pulses arrive, the counter 3 operates in the summation mode. With the arrival of 32 pulses, the trigger of sign 8 enters state 1 and counter 3 operates in subtraction mode. In this case, a positive half-perist sinusoid is formed from 64 pulses. Then 64 pulses the trigger of sign 8 is set to the state O and the counter 3 again operates in addition mode, 64 impulses the trigger of the reverse polarity 9 goes to state 1 and on the output block 10 consisting of a summing device and a correction block the voltage is obtained of opposite polarity With the arrival of 96 pulses, the reversible counter 3 again goes into subtraction mode, and on receipt of 128 pulses, the formation of one sinusoid period is completed. The output unit 10 with the delay unit 11 provides a smooth increase in the amplitude of the sinusoid from 0 to the maximum value at the beginning of the sweep and a smooth decline after the arrival of the command at its end.

Frequency band formed by. digital-to-analog converter, which

used in a sweep generator to control the source of seismic signals of vibration, with predetermined characteristics, completely covers the entire working range of vibration seismic prospecting.

Claims (2)

1. USSR Author's Certificate No. 358778, cl. H 03 K 13/03, 1973. 2. USSR author's certificate N 361518, 15 cells. H 03 K 13/03, 1973. (prototype).