SU1693509A1 - Device for measuring physical values - Google Patents

Abstract

This invention relates to electrical measuring technology. To improve measurement accuracy by reducing the effect of temperature instability and the effect of temperature on the measurement results, the device contains a self-oscillating generator, a sensor, a single vibrator, a capacitor switched on during the driving circuit of a single vibrator and a logic element EXCLUSIVE AND PI, one of the inputs of which is connected to output of the one-shot, a pulse shaper, a NOT element, an AND element and a descending unit containing the first, second AND-NOT elements, sequentially connected reversing meter, digital channel voltage converter and voltage converter. 1 hp pl, 3 silt, cl

Description

The invention relates to electrical measuring equipment and can be used to measure various physical quantities, in particular continuity, gas content, liquid level by measuring volume resistance in the study of a conductive liquid or container in the study of a nonconducting liquid.

The purpose of the invention is to improve measurement accuracy by reducing the effect of temperature instability and the electrical properties of a liquid and reducing the effect of polarization on the measurement results.

FIG. 1 is a block diagram of a device for measuring physical quantities; in fig. 2 - timing diagrams for the operation of the device; in fig. 3 shows an example of a self-oscillating generator with a pulse driver and a sensor connection.

A device for measuring physical quantities contains a sensor 1, a self-oscillating generator 2, a pulse shaper 3, a one-shot 4, a reference capacitance 5, a logical element EXCLUSIVE OR 6, an element AND 7, an element NOT 8, a tracking unit 9 consisting of the first 10 and second 11 elements of NAND, reversible counter 12, digital-to-analog converter (DAC) 13 and voltage-current converter 14. The inputs of the NAND elements and the input of the element are NOT Connected to the device control bus 15.

Sensor 1 is turned on during the master circuit of the self-oscillating generator 2, the output of which is connected via the driver 3 to the input of the one-shot 4 and the second input of the EXCLUSIVE OR element 6.

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The output of the one-shot 4 is connected to the first input of the EXCLUSIVE OR element 6, the first output (Outlet, 1) of which is connected to the first input of the AND 7 element, the output of which is the device output, and the output of the HE element 8, the input of which is simultaneously connected With the second outputs of the elements, AND-NE 10 and 11 is connected to the bus 15 of the control of the Calibration-Measurement device, the first inputs of the elements AND-NE 10 and 11 of the tracking unit 9 are connected respectively to the second (Out 2) and third (Out 3) outputs of the element EXCLUSIVE OR 6. In block 9 tracking output The first 10 and second 11 bits of the IS-NOT are connected respectively to the outputs G and -A and the reversing counter 12, the outputs of which are connected to the digital inputs of the D / A converter 13.

The analog output of the CDL 13 is connected to the input of the voltage-current converter 14, the output of which, being the output of the tracking unit 9, is connected to the reference capacitor 5, the timing circuit of the single-oscillator 4.

The EXCLUSIVE OR 6 element can be performed, for example, as follows: two elements NOT 16 and 17, two elements AND 18 and 19 and element OR 20. The input of element NOT 16 and the first input of element AND 19 are the second input of element EXCLUSIVE OR 8. The input element NOT 17 and the first input element AND 18 are the first input element EXCLUSIVE OR 6, the second inputs of elements AND 18 and 19 are connected respectively to the outputs of elements NOT 16 and 17, and the outputs of elements AND 18 and 19 to the inputs of elements OR 20. The output of the latter is the first output (Ex. 1) of the item EXCLUSIVE OR 6. The second the output of the EXCLUSIVE or 6 element (Out. 2) is the output of the element And 18, and the third (Out. 3) - the output of the element I 19.

An example of the implementation of the scheme of the self-oscillating generator 2 with the sensor 1 and the driver of the 3 pulses is shown in FIG. 3

The self-oscillator generator 1 is made on operational amplifiers (repeater 21 and comparator 22). The timing of the driver circuit consists of the resistance Rg sensor 1 and capacitance C 23. The positive feedback of the comparator is formed by resistors 24 and 25. Zener diodes 26 and 27 serve to stabilize the voltage in the feedback circuit. Transistors 28 and 29 provide the necessary load capacity of the circuit. The two-pole voltage signal converter from the output of the self-oscillating generator 2 to the unipolar one is carried out by the driver 3, made on the elements 30-33. In the case of operation of a device with a capacitive sensor, it is switched on instead of capacitance 23, and instead of a resistance sensor Rg a constant resistor is connected.

In the tracking unit, opamp amplifiers can be used as a voltage-current converter 14 in combination with an emitter follower.

The operation of the device is illustrated by the example of measuring gas content in a fluid flow using timing diagrams shown in FIG. 2, where the following symbols are used: 5

a - output signal of the self-oscillator generator 2 (Ite);

b - signal at the non-inverting input of repeater 21 (UBx2l);

0 in - the output signal of the driver 3 pulses (U);

g - output signal of one-shot 4 (U4);

d - output signal from the second output 5 (OUT. 2) of the element EXCLUSIVE OR 6

(willow);

e is the output signal from the third output (Ex. 3} of the EXCLUSIVE OR element 6 (yeah);

0 W - voltage-current converter output signal (S);

h - output signal from the first output (OUT. 1} of the EXCLUSIVE or 6 element

(ibyyh1);

5 and - the output signal of the device (U).

In the course of physical research, for example, measuring the percentage of gas in a gas-liquid mixture, the measurement time is usually much less

0 wait time. In this case, during a wait, a continuous liquid flow can pass through the sensor, and when a gas mixture enters the liquid flow, the measurement mode is automatically switched on, for example, by some command, the electropneumatic valve turns on and supplies the gas flow, and switches on the measurement mode with its limit switch. Electrical properties of a fluid, for example, volume

Conductivity and dielectric constant can vary slowly depending on temperature and fluid composition, and deviations of these parameters can reach tens of percent per hour.

5 In this case, the known use of the reference sensor is often difficult due to the impossibility of placing it in equal conditions with the measuring sensor, and manual calibration, for example, by changing the capacitance turned on during the master circuit of the one-shot 4, is ineffective if the start of measurements is not predetermined .

Due to the introduction of the watch unit 9 in the standby mode, the reference value of the pulse width generated by the single vibrator 4 (Fig. 2d) is automatically generated and stored for the measurement time. This standby duration is automatically maintained regardless of a change in the electrical properties of the fluid equal to the pulse duration formed by the self-oscillating generator 2 (Fig. 2c) at a zero value of the measured value, for example, at 0% of the gas content in the liquid. The frequency of the self-oscillator generator 2 is determined by the parameters of sensor 1.

The bipolar pulses (Fig. 26) are exponential in nature, are close to triangular in shape, through repeater 21 are fed to the input of the comparator 22, from the output of which the bipolar rectangular signals (Fig. 2a) are fed through transistors 28 and 29 during setting the circuit in which the sensor 1 enters, and not the driver input 3.

From the output of the imaging unit 3, a single-field signal with a positive front (Fig. 2c) starts the one-shot 4.

The duration of the pulses produced by the single vibrator 4 (Fig. 2d) is determined by the value of the capacitor 5 and the charge current supplied from the voltage-current converter 14 (Fig. 2g) of the tracking unit 9.

The pulses from the imaging unit 3 (Fig. 2c) and the pulses from the one-shot 4 (fig. 2t) arrive at the second and first inputs of the EXCLUSIVE or 6 element, respectively. In case of equal duration of these pulses, the signals at the outputs of the EXCLUSIVE OR element b will be absent (Fig. 2 d, e, and, e).

If for some reason the volume conductivity decreases or the dielectric constant of the test liquid increases, the pulse duration at the output of the shaper 3 (Fig. 2c) will be longer than the pulse duration at the output of the one-vibrator 4 (Fig. 2d). As a result, the outputs of the Ex. 1 and Ex. 3 elements EXCLUSIVE OR 6 in terms of differential pulse (Fig. 2 h, e).

If the volume conductivity increases or the dielectric constant decreases, the pulse duration at the output of the imaging unit 3 (Fig. 2c) will be less than the pulse duration at the output of the one-shot 4 (fig. 2d). As a result, the differential pulse is obtained at the outputs of the Out.

1 and Ex. 2 elements EXCLUSIVE OR b (figure 2 h, d).

The device has two modes of operation.

In calibration mode at the bus inlet

15 control calibration measurement

there is a logical unit signal.

incoming to control unit 9

tracking and entry element is NOT 8. At the same time

Element And 7 is closed by a logical zero signal arriving at its second input.

from the output of the element is NOT 8, and the elements are NOT

10 and 11 are opened by a logical signal.

units entering their second entrances.

Depending on which of the outputs of the EXCLUSIVE OR 6 element appears pulses (Fig. 2e, e), the reversible counter 12 begins to work in addition or subtraction mode, causing a code change on its output: This, in its

0 queue, changes the voltage at the output of the DAC 13 and the magnitude of the current at the output of the voltage-current converter 14 (Fig. 2g).

If the pulse duration at the output of the driver 3 pulses will be

5 is longer than the pulse duration at the output of the one-shot 4, the current will decrease, if more, then the current will increase, which will equalize the duration of these pulses. After this, the device is ready for operation.

0 in Measure mode.

In the Measurement mode at the input of the bus 15 of the control Calibration-measurement, a logical zero signal is present, which is fed to the control input of the block 9

5 watches, i.e. to the second inputs of the first 10 and second 11 elements NAND and the input of the element NOT 8. At the same time, the signal at inputs -1 and +1 of the reversing counter 12 is not received, since the elements NID 10 and 11 are closed

0 signal logic zero. Simultaneously with this element, AND 7 is opened by the signal of a logical unit coming from its output to the second input of the element 8, and the pulses whose duration is proportional to

5 to the measured value, from the first output (Out. 1) of the logic element EXCLUSIVE IL AND 6 through the element AND 7 arrive at the VUKHOD of the device. In the future, these pulses can be converted into a code or d analog value for processing on a computer, or recording with a voltmeter, or for recording on a loop oscilloscope.

When conducting various physical studies, it is necessary to determine the gas content, continuity, level and other parameters of both conductive and non-conductive liquids. In this case, measurements can be made both by command and automatically by a given sequence diagram,

Due to changes in the environmental conditions, such as temperature, or the composition of the liquid due to the occurrence of any inclusions, or when the composition changes according to the experimental conditions, the dielectric constant and conductivity of the liquid change. This necessitates calibration prior to direct measurement. Calibration is especially necessary when the probability of a change in temperature or fluid composition is greater between measurements than during measurements, i.e. when the measurement time is shorter than the waiting time,

In the proposed device, due to the introduction of the tracking unit, an automatic calibration of 0% gas content, or 100% liquid continuity, or 100% liquid level is performed regardless of the temperature or composition of the liquid, which leads to an increase in measurement accuracy due to a decrease in the effect of temperature instability or electrical properties fluid on the measurement results

In addition, the implementation of a self-oscillating generator with the possibility of bi-polar powering of the measuring sensor leads to an additional increase in the accuracy of measurements by reducing the effect of liquid polarization on the results of measurements.

Claims (1)

1. A device for measuring physical quantities, comprising a self-oscillating generator connected to a sensor, a one-shot, a capacitor switched on in time to set the one-shot circuit, and an EXCLUSIVE OR element, the first input which is connected to the output of a single / .brater, characterized in that, in order to improve the measurement accuracy of aa account to reduce the influence of temperature instability and electrical properties of the headlessness, a pulse former, an element HE, an AND element and a tracking unit containing the first, second IS-NOT elements connected in series to a reversible counter, digital-to-analog converter and voltage-current converter, the outputs of the first and Voooo) I-HL element are connected to the inputs of the reversible counter, the output of conversion bodies is voltage The current, which is the output of the tracking unit, is connected to the capacitance of the one-vibrator driving circuit, while the output of the auto-oscillator is connected to the input of the pulse former, the output of the latter is connected to the single-vibrator input and the second input of the SPARKING OR element, whose outputs connected: the first to the first input of the AND element, the second to the first input of the first element of the IS-NOT tracking unit, the third to the first input of the second element of the IS-NOT of the tracking unit, the second input of the indicated AND NOT elements and the input of the element are NOT connected to the bus device control, and the output of the element is NOT connected to the second input of the AND element, the output of which is the output of the device. 2, The device according to p, 1. About tl and h and y shch about e- with those. 1 that, in order to reduce the effect of the polarization of the liquid on the measurement results, the timing of the self-oscillating oscillator circuit is connected to its dual output. 3f well i i with WITH J l & ftl ± I SL "H, 5Q " s d WITH J  j Fig.Z 51