SU758063A1 - Null-indicator - Google Patents

Description

The invention relates to the field of automation, electrical measuring and computing equipment and can be used in the construction of analog-digital converters and in automatic control systems.

Three main types of nullorgans are known: regenerative, direct amplification, and pulsed.

Regenerative zero-bodies are characterized by the presence of non-linear positive feedback between the output and the input, which causes a sharp change in the output signal when the input signal is equal to zero, and consist of a wideband non-inverting amplifier with a common deep negative feedback and a positive feedback circuit. capacitive bandpass filters, amplifier-limiter, low-pass filter, high-frequency filter modulator [1 ^.

The disadvantage of the null-organ of this type is the low stability and the sensitivity of fixing the zero value of the input voltage.

Known null body direct amplification, consisting of an operational amplifier, driver, source 30

^ voltage threshold, switch, threshold element and filter has significant amplifier zero drift [2]

Modulated null-bodies consisting of a modulator, a control generator, an AC amplifier, a high-frequency modulator, a threshold element, AND, NOT-AND, OR elements, a reversible binary counter do not have a zero drift, and therefore have a higher accuracy. However, they have a lower speed, depending, in particular, on the modulation frequency [3].

The closest in technical essence to the proposed is a null-organ, which consists of a vibration converter, a control generator, an alternating current amplifier, a modulator, a higher frequency generator, threshold circuits, a voltage-voltage converter, the first input of the modulator is connected to the output of the high-voltage generator frequency, the second input of the modulator is connected to the output of the AC amplifier, and the output of the modulator is connected via a threshold circuit to the converter of the number of pulses into voltage, connected omu with manage ""

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generator and the second threshold scheme [4].

This zero-body does not have the disadvantages inherent in the listed analogues, but it does not have a sufficiently clear zero voltage fixation and a complex scheme.

The aim of the invention is to improve the accuracy of fixing zero voltage and simplify the null organ.

This goal is achieved by the fact that in the null-organ containing the modulator, the first input of which is the input of the zero-organ, the second input is connected to the output of the high-frequency generator, and the output of the modulator is connected to the input of the amplifier-limiter, and a pulse shaper, dividing diodes are introduced modulo two logic element and pulse selector for duration, the output of which is the output of a nud-organ, and the input is connected to the output of the logic element of the addition modulo two, the first input of which through the first will divide flax diode connected to the output usilitelyaogranichitelya second logical addition element modulo two input connected to the output pulse generator, a second input connected through a diode to the output of separating a high frequency generator.

FIG. 1 shows a functional diagram of the zero organ; Fig. 2 shows graphs explaining his work.

The input 1 of the zero-organ is connected to the input of the modulator 2, the output of which is connected to the input of the amplifier-limiter 3 AC. The output of the high-frequency generator 4 is connected to the second input of the modulator 2 and through the separation diode 5 and the pulse shaper 6 to the first input of the addition logic element 7 modulo two. The second input of the logic element 7 is connected via a separating diode 8 to the output of the amplifier-limiter 3, and the diodes 5 and 8 turn on in one direction. The output of the logic element 7 is connected with the input of the selector 9 pulses in duration, the output of which is connected to the output 10 of the zero-body.

The proposed zero-body works as follows.

The input is a slowly varying signal from input 1 to the input of modulator 2 and modulates in it the reference voltage supplied to the second input of the modulator from the output of the high-frequency generator 4. Then the modulated signal is amplified and limited in amplitude by the amplifier of the limiter 3 AC. Amplitude limitation is necessary to match the logical input.

element 7 with the output of the amplifier 3 and for the formation of rectangular pulses in order to improve the accuracy of fixing the zero value of the input voltage.

Positive half-periods of a sine wave. Ideal reference voltage from the output

the generator 4 after the diode 5 is fed with a frequency to the input of the pulse shaper 6, where it is also converted into rectangular pulses in order to improve the accuracy of fixing the zero value of the input voltage.

From the output of the pulse shaper

6 rectangular positive pulses arrive at the first input of the addition element 7 modulo two.

NSG ^ the second input of the logic> element ~ -7 also receives rectangular positive pulses through the diode

eight.

Logic element 7 implements a logical addition function modulo two: \ _g k · ₂ , where x ,, x ₄ is its

input signals.

At the moment when the signal passes through the zero, the phase of the modulated voltage changes by 180 ° and prior to the phase change, the inputs of element 7 receive such combinations of input signals (11 or 00) _, which does not produce an output signal at its output.

After the phase changes by 180 ° (i.e., the input voltage becomes zero), to the inputs of the element

7 will receive a combination of signals (10 or 01), in which at its output will appear pulses, signaling the transition signal through zero.

In reality, until the signal passes through zero, short pulses will occur at the output of logic element 7, the duration of which is determined by the difference in delays between the circuits 2, 3, 8 and 5, 6 (see Fig. 2, ₇ ). The duration of these pulses is much less than the duration of the main pulses that carry information about the moment of signal zero crossing. The pulses from the output of the element 7 are fed to the input of the selector 9 pulses of duration 9, which "filters out" minor pulses, and informative pulses pass to the output 10 of the zero-body.

The advantage of the proposed nullorgan is the simplicity of its circuit design, the accuracy of fixing the zero value of the input voltage. The speed of the zero-body depends on the frequency of the reference voltage.

At present, modern element base (for example, integrated circuits) allows the use of a reference voltage of up to 6 MHz and test data, which guarantees high accuracy and speed of this null organ.

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Claims (1)

Claims of Invention Null-organ containing modulator, the first input of which is the input of the zero-organ, the second input is connected to the output of the high-frequency generator, and the output of the modulator is connected to the input of the amplifier-limiter, and a pulse shaper, characterized in that, in order to improve the accuracy of zero-voltage fixation and simplification 10 null-organ, dividing diodes are introduced into it, a logical element of addition modulo two and a pulse selector by duration, the output of which is the output of a zero-body, 15 and the input is connected to the output of the logic element of addition modulo two, ne the left input of which is connected to the output through the first isolation diode 20 the limiting amplifier, the second output of the logic element of the addition of module two is connected to the output of the pulse shaper, the input connected through the second separation diode to the output of the high-frequency generator.