RU1831668C - Gauge for measurement of pressure - Google Patents

Abstract

The invention relates to measuring and control equipment and can be used for indicating and monitoring pressure in systems for technical diagnostics of the current state of equipment operating in industries related to the receipt, storage or processing of explosive substances. The electronic pressure gauge contains a primary measuring transducer, including an elastic element connected by a rod with a differential inductive half-bridge of the electronic signal processing unit, a functional converter, and an intrinsic safety unit. a limit switch, an indicator of an average pressure value indicating an instrument. The pressure gauge allows you to control several types of pressure parameters, for example, its average value in integral expression for a certain time interval, the mean square pressure pulsation, peak values at the maximum and minimum, peak parameters with time and amplitude characteristics, etc. 4 il. THX

Description

The invention relates to measuring equipment and, in particular, to devices for measuring pressure parameters pulsating during operation of technological equipment. It can be used for technical diagnostics of the current state of this equipment and as a measuring and signaling device, the sensors of which can be installed in explosive rooms.

SUMMARY OF THE INVENTION

The insufficient number of output parameters, the low speed of the known measuring transducers of pressure into electrical signals and the absence of explosion protection do not allow the registration of pressure pulsations in terms of explosive industries according to their frequency characteristics, the moment of occurrence of pressure pulses and drops, as well as their average or average quadratic values. However, such data are necessary for the analysis of the current technical condition of technological equipment. alternating detect it razvivayuschihs defects, accident prevention and the translation methods of repairing of PPR (preventative maintenance) cycles for repairs on the actual technical state of the. Fulfillment of the last conditions gives economic

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the means by reducing equipment repair cycles, preventing and eliminating industrial accidents.

The proposed device ensures the intrinsic safety of the circuits of its sensors and allows the use of elastic elements with increased stiffness in them, which make it possible to reproduce in mechanical displacements all the necessary high-frequency components of pressure pulses and transfer them to a ferromagnetic core with a mass significantly less than the mass of the elastic element, and to convert all its small movements into electrical signals by an electronic inertia-free device into their corresponding pulsed, frequent tnye and averaged parameters of pressure with minimal interference.

Thus, the essence of the invention is to provide explosion protection and to increase the accuracy of measuring pressure parameters in its fast processes, the sensitivity of an electronic transducer of small displacements into an output noise-resistant current signal for using the device in conditions of chemical, oil refining and other industries with increased explosion risk.

The essential features of the invention are that the pressure measuring device comprises a primary measuring transducer (sensor) and a secondary functional transducer connected in series, connected by a communication line, where the sensor contains an elastic element that converts the pressure of the controlled medium into movement, and the ferromagnetic core connected with it, placed in a double-winding coil connected to the unit for converting the movement of the core into an intermediate DC signal, and in The toric functional converter comprises an intermediate signal amplifier, an alarm set point assembly, and an indicating device.

A distinctive feature of the device is expressed in that the core displacement conversion unit and the direct current signal contain a high-frequency voltage amplitude controlled oscillator, the feedback loop of which includes coil of the sensor coil, and the operational amplifier of the generator contains input signal differentiation circuits. wherein the shaper of the output current signal, the circuit of which includes a threshold element connected to the primary winding of the output transformer for generators, provided with a current pulse amplifier and a resistor mounted in the circuit

of this amplifier and at the same time included in the bias voltage source of the threshold element, and the pulsed current transformer of the same amplifier is connected by its secondary winding via a balanced resistor to the secondary winding of the generator output transformer and to the sensor windings connected to it, and the primary winding of the pulse transformer is separated from

5 of the filter circuit of the constant component of the current signal by a capacitor, which is connected through the communication line to a functional converter to a resistor, included in the load circuit of the current signal and inserted into the intrinsic safety unit installed at the input of the converter, the output of which is connected through the signal repeater with a pulse output of the device and with measuring 5 circuits of the transducer, which include an integrator of average pressure, a detector of average qsdratic value of pressure pulsation, and maximum and minimum detectors

0 extreme values of the pressure output signal, as well as a circuit switch included in the serial circuit of the integrator and indicating device.

In FIG. 1 shows a primary measuring transducer (sensor); in FIG. 2 - full functional diagram of the device; in FIG. 3 is a schematic diagram of a sensor signal processing unit; in FIG. 4 - schematic diagram of the functional

0 converter

The primary measuring transducer (FIG. 1) contains a housing 1, a connecting fitting 2, an elastic element 3 connected via a cable 4 to a double-winding coil 5 made according to a differential winding circuit, and a signal processing unit SLR b connected via a communication line 7 (Fig. 2) with a functional Converter 8.

0 Intrinsic safety unit BIV 9 is installed at the input of converter 8. The power supply circuits are connected to the converter, 8 are also connected from the intrinsically safe power supply 10. The inclusion of the intrinsic safety unit 9 is optionally combined with the conversion of the intermediate sensor current signal into a voltage signal. The output of the BIB 9 through the button switch KP 11 is connected to the integrator 12 of the average value of the measured pressure,

the integrator’s output is connected to a indicating device 13. In parallel with the output of the BIB 9, detectors of the RMS mean square value RMS 14 of pressure pulsation, extreme values at the maximum peaks of EDmax 15, and minimum peaks of Edmin 16 are connected. In addition, in the converter 8 the alarm settings block Ust 17 and two comparators K-pmax 18 and K-rmin 19. Their outputs 20 and 21 are for connecting external signaling devices. The SLA signal processing unit 6 of FIG. 1 contains an electronic device (Fig. 3) equipped with a high-frequency voltage-controlled harmonic oscillator, consisting of an operational amplifier 22, equipped with an input differentiating circuit in the form of a capacitor 23 and a resistor 24, and an oscillating circuit with an inductance 25 and a capacitor 26 . To the output of the amplifier 22 through the isolation capacitor 27 is included the primary winding 28 of the output transformer 29 of the oscillator. A threshold element is connected to terminal 30 from the winding 28 - a transistor 31, equipped with a bias voltage source made on resistors 32, 33 and 34. The capacitor 35 blocks the resistor 34, which is connected to the second input of the amplifier 22 as a reference voltage source, and the capacitor 36 blocks the resistor 32. connected to the base of the transistor 31. A current pulse amplifier is connected to its collector - a transistor 37 with a resistor 38 containing a resistor 39. An amplifier is installed in the current circuit and is simultaneously connected to the voltage source place the threshold element on the base of the transistor 31 through the resistor 32 and the capacitor 36. The primary winding 40 of the pulse transformer 41 is connected to the collector circuit of the transistor 37 of the current pulse amplifier, shunted by the diode 42 and the quotation resistor 43. A resistor 44 and a capacitor are included in the series circuit with the winding 40. 45, separating the variable and constant component circuits of the current pulses. A DC converter filter is included in the DC circuit, consisting of capacitors 46, 47 and a resistor 48 connected to an external circuit terminal 49 with a communication line 7 and a load resistor RH. The secondary winding of the output transformer 29 of the generator 22 contains sections 50 and 51 connected through a quotation resistor 52, actuated by a third section 53. Connected to a quotation resistor 52

secondary 54 is the winding of the pulse transformer 41 included in the negative feedback circuit by self-excitation of the oscillator 22. To the windings 50 and 51, 5 are connected the windings 55 and 56 of the sensor 57, connected to the elastic element 3 via communication 4 (Fig. 1).

The communication line 7 (Fig. 2) is connected to the input 58 (Fig. 4) of the intrinsic safety block

0 BIB 9. containing (as required by GOST 22782.5-78) a current-limiting resistor 59 and a zener diode 60. A resistor 61 is included in the load circuit of the current signal circuit, as well as a resistor 62 and diodes 63 and 64. Output

5, BIB 9 is connected to the input of signal repeater 65, which is built on an operational amplifier and has a high input resistance. Its output bb is the output of a pulse signal, to which additional diagnostic equipment can be connected (e.g., oscilloscope, spectrum analyzer, etc.). In the device, the output 66 is connected to the push-button switch 67-71 and through it with the input of the integrator 12 containing the operational amplifier 72, resistors 73, 74 and a capacitor 75. An indicating device 13 is connected to the output of the integrator.

In parallel to point 66, a quadratic mean pressure pulsation detector connected to an operational amplifier 76 with resistive circuits 77-81, diodes 82, 83 and an isolation capacitor 84 is connected. To operational amplifiers 85 and 86 equipped with electronic switches 87 and 88 made circuits of detectors of maximum and minimum levels of the pressure signal with resistive circuits 89-94, diodes 95, 96 and

0 capacitors 97, 98 connected to the buttons 68 and 69 of the switch.

The controllers of the alarm settings 99, 100 are connected in parallel with the buttons 70 and 71 and the inputs of the comparators 101, 102 s

5 resistors 103-106. Comparators together with transistors 107, 108 and relays 109, 110 with contacts 20, 21 Form signaling nodes 18 and 19 (Fig. 2).

The device operates as follows.

The harmonic oscillator generated on the operational amplifier 22 is self-excited through a positive feedback circuit arising from the initial unbalance of the bridge circuit formed by the secondary windings 50.51 and 53 of the transformer 29 with the resistor 52 and the windings 55, 56 of the sensor 5. The unbalance is regulated by the resistor 52 . In series with the positive feedback circuit acts on the input of the generator 22, the negative feedback circuit formed by the winding 54 of the pulse transformer 41. of positive and negative feedbacks, the condition of self-excitation of the oscillator is determined by the amplitude balance, the phase balance is set by switching on a differentiating circuit consisting of a resistor 24 and a capacitor 23. As the amplitude of the self-oscillations develops, a threshold element 31 and a current pulse amplifier 37 are opened in the circuit which generates a cosine wave current pulse. The value of the cutoff angle of the cosine pulse is set from the voltage divider on the resistors 32, 33.34 and 39 in total with the voltage np of the junction of the transistor 31 and the voltage taken from the tap 30 of the primary winding 28 of the transformer 29. Within the cutoff angles 18-20 The constant component of the cosine current pulse with sufficient accuracy for many technical measurements is proportional to the amplitude of its first harmonic, from which a negative feedback action is formed in circuit 25.26. From the voltage drop across the resistor 39, a correction is made in proportion to the strength of the pulse current for the accuracy of the pulse formation in the cutoff angle. As a result, the generated voltage is stabilized, which in turn depends on the degree of further imbalances in the inductances of the windings 55, 56 of the sensor 5 depending on the displacements of its core 57, which leads to a corresponding change in the direct current at the output 49 of the filter 46, 47, 48.

Taking into account the fact that in the considered circuit the oscillator always operates in the generation threshold mode, which is automatically regulated by the actions of two feedbacks, its gain with respect to the voltage difference of these bonds tends to infinity and is practically independent of the signal transfer coefficient in the amplifier 22. Therefore, temperature drifts of semiconductor device modes have minimal effect on conversion accuracy. The main stabilization of the operating mode of the converter is achieved here by the stability of the operation of its winding elements in their transformation coefficients and by the stability of the resistors included in the voltage dividers.

The zero balance in the circuit is performed by the resistor 52. Regulating the conditions for the onset of self-excitation, and the sensitivity by the resistor 43, which shunts the primary winding 40 of the pulse transformer 41. An increase in noise immunity is achieved here by current signal transmission

along the communication line, since the constant component of the current pulses does not depend on the value of the load resistance at the output 49.

Low inertia in the transmission of motion signals is achieved by the fact that the generator operates at frequencies of the order of 0.25-1.0 MHz. This condition allows obtaining information on pressure pulses in a wide spectrum of low frequencies with respect to

5 generator frequency.

The current signal supplied to input 58 (Fig. 4) creates a voltage signal on resistor 61. Its value does not exceed the voltage of unlocking of the zener diode 60 and

0 is transmitted through a resistor 59 to the high-impedance input of the repeater 65. BIB 9 is constructed from the hypothesized condition of the occurrence of a random breakdown of isolation and the ingress of alternating current with a voltage of 250

5 V to the output of the BIB 9. In this case, the resistor 59 limits the current strength, and the zener diode 60 limits the residual voltage, which is not passed through the resistor 62 and diodes 63 and 64 to the input 58, which meets the requirements.

0 presented to the intrinsic safety of the measuring circuit in accordance with GOST 22782.5-78.

Under normal operating conditions and when the buttons 67-71 are released, the signal from the output of the repeater 66 comes directly

5 to the input of the integrator 12, which in this case gives a voltage proportional to the average value of the pressure on the indicating device 13. In parallel with the output 66, the signal is fed to the RMS detector

0 14 (Fig. 2), where (in Fig. 4), only the variable component is extracted from the signal through the capacitor 84, which is supplied to the button 67 through a direct circuit through the resistor 80 and through the half-wave amplifier 76 and

5 is a resistor 80. Both circuits are balanced by a resistor 78 so that the amplitude of the amplified signal is twice the amplitude of the direct one. Then, when button 67 is pressed, the summation of these amplitudes

0 of the current in the integrator 12, at the output of which a signal is generated proportional to the average value of the half-wave rectification of the variable component of the pressure pulsation, which is equalized by scaling to the RMS of the harmonic signal.

The extreme detector EDmax 15 opens with an amplifier 85 an electronic switch 87, when the voltage at the output 66 exceeds the voltage by

the capacitor 97. Then, with the switch 87 open, the capacitor is recharged to the maximum voltage level, and then, when the voltage at the output 66 drops, the amplifier 85 locks the key 87 through the diode 95 and leaves a charge on the capacitor. The discharge of the capacitor 97 is through its resistive loads. When the button 68 is pressed, the voltage of the capacitor is fed to the input of the integrator 12 and through it to the indicating device 13.

The alarm limit is set by pressing the button 70 by rotating the handle of the resistor 99, the voltage from which goes to the integrator 12 and is controlled by the device 13. During operation, the voltage of the set point and capacitor 97 are compared by a comparator 101 equipped with a signaling device 20.

A similar circuit works ED-min 16 with an amplifier 86.

This ensures explosion protection and increases the accuracy of measuring pressure parameters in its fast-flowing processes, the sensitivity of the electronic transducer of small displacements into an output noise-resistant current signal, which allows the use of the device in conditions of chemical, oil refining and other industries with increased explosion risk.

Claims (1)

SUMMARY OF THE INVENTION A pressure measuring device comprising a primary measuring transducer connected in series through a communication line in the form of two differential-inductive windings arranged on a farm-shaped core connected to an elastic element a pressure sensor included in the feedback circuit of an amplifier in a controlled high-frequency alternating voltage generator, in the amplitude control circuit 5 of which an output signal detector is connected, and a secondary functional converter with an integrator output connected to a indicating device. characterized in that in the secondary 0 functional converter, a spark-protection circuit is connected in series, the input of which is the input of the functional converter, a matching amplifier and switch, the output of which is connected to the integrator input, as well as the rms values of the maximum and minimum ripple amplitudes with signaling devices connected between the output of the spark protection circuit and corresponding additional inputs of the switch, the output signal detector is made in the form of a threshold element associated with the primary generator transformer winding 5 high-frequency alternating voltage, a current pulse amplifier with a pulse transformer, an output connected to the bias control circuit of the threshold element, in series 0 pulse current transformer, load resistor, isolation capacitor, and low-pass filter included in the primary winding of the pulse transformer, the output of which is the output of the primary measuring transducer, while the secondary winding of the pulse transformer is connected to the secondary winding of the transformer of the high-frequency alternating current generator 0 voltage, the amplifier of which is made in the form of an operational differentiating amplifier. Yu FIG. 1 twenty 21 Fig. I S2  j Fig- $ -, $ VL B 68 69 JO n h j ni. rilJTI l / g b / x pj. , ..  T I pit .. 7S 7P 106 18 & FIG 4