CN210833767U - Static capacitance liquid level meter with temperature self-regulation - Google Patents
Static capacitance liquid level meter with temperature self-regulation Download PDFInfo
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- CN210833767U CN210833767U CN201921514115.7U CN201921514115U CN210833767U CN 210833767 U CN210833767 U CN 210833767U CN 201921514115 U CN201921514115 U CN 201921514115U CN 210833767 U CN210833767 U CN 210833767U
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Abstract
The utility model discloses a static capacitance level gauge with temperature self-interacting, including terminal box, temperature sensor, flange, temperature sensor and control chip, control chip on be provided with power, capacitance frequency converter, AVR singlechip processor, capacitive sensor and digit ware that shifts, the power be connected with capacitive sensor and AVR singlechip processor respectively, capacitive sensor be connected with AVR singlechip processor through capacitance frequency converter, AVR singlechip processor be connected with the digit ware that shifts, temperature sensor set up the lower part in gathering the electrode and be connected with power and AVR singlechip processor respectively. In this way, the utility model provides a static capacitance level gauge with temperature self-interacting has reached that the output value does not change along with the change of humidity, improves the measurement accuracy of actual liquid level, improves the life and the security of product.
Description
Technical Field
The utility model relates to an industrial automation's field especially relates to a static capacitance level gauge with temperature self-interacting, belongs to instrument and meter, directly is applied to trades such as water treatment, chemical industry, boats and ships, oil, bio-pharmaceuticals, environmental protection, municipal administration, food.
Background
1) Instrumentation and local automation (50-60 years in 20 th century)
Before and after the 50 s of the 20 th century, capacitive level gauges began to be developed in process control. Some plant enterprises implement instrumentation and local automation. This is the first stage in the development of process control for capacitive level gauges. The main features of this stage are: the adopted process detection control instruments are foundation-type instruments and partial unit combined instruments, and most of the instruments are pneumatic instruments; the structure of the process control system is mostly a single-input-single-output system; the controlled parameters are mainly liquid levels, and the purpose of control is mainly to keep the stability and accuracy of the process parameters and ensure the production safety.
2) Integrated automation (middle of 60-70 s in 20 th century) stage
In the 60 s of the 20 th century, with the continuous development of industrial production, new requirements are put forward on a capacitance type liquid level meter; the rapid development of electronic technology also provides conditions for the continuous improvement of the automatic technical tool, and the magnetic float liquid level meter starts to enter the second stage. In this stage, the industrial production process is comprehensively automated from a workshop to a factory, and is mainly characterized in that: a large number of unit cluster meters (both pneumatic and electric) and modular meters are used. Meanwhile, computers have begun to be used in the field of Process Control, implementing Direct Digital Control (DDC) and Set Point Control (SPC). In the aspect of the structural scheme of the process control system of the automatic instrument, various complex control systems such as cascade control, feedforward-feedback composite control, Smith estimation control, ratio, uniformity, selectivity control and the like appear in succession, so that on one hand, the control quality is improved, and on the other hand, some special control requirements are met. The analytical and comprehensive theoretical basis of the automatic instrument control system is developed from a classical control theory to a modern control theory. The control system is shifted from a univariate system to a multivariable system to solve the more complex problems encountered in the production process.
3) Full automation (20 th century 70 middle to present) stage
With the rapid development of modern industrial production, the development and application of microcomputers go through three stages since the middle of the 70 th 20 th century:
the main characteristics of the first stage are as follows: in the aspect of a novel automatic technical tool, an intelligent unit combination instrument (comprising a programmable controller and the like) taking a microprocessor as a core is adopted; the application of online component detection and data processing is increasingly wide; the variety of the analog regulating instrument is continuously increased, the reliability is continuously improved, the capacitive liquid level meter also realizes the intrinsic safety explosion prevention, and the requirements of various complex process control are met. In the aspect of the structure of a process control system, a single variable control system is developed into a multi-variable system, a fixed value control of a production process is developed into an optimal control and a self-adaptive control, and an automatic instrument control system is developed into a computer distributed control system and the like. In the aspect of application of a control theory, the modern control theory is transferred to the field of process control, such as application of state feedback, optimal control, decoupling control and the like in process control, and development of control technologies and theories of process modeling, testing, control method design, analysis and the like is accelerated.
Capacitive level gauges have currently entered the Computer age, entering the age of the so-called Computer-Integrated Process control System (CIPS). The CIPS utilizes a computer technology to comprehensively manage and control the operation process of the whole enterprise, including the overall processes of marketing, production plan scheduling, raw material selection, product distribution, cost management, control, optimization and management of the technological process and the like. Distributed control systems, advanced process control strategies, as well as network technologies, database technologies, etc. will be an important basis for implementing CIPS. It can be expected that process control will be developed more rapidly in the modernized construction process of the socialist of our country.
The capacitance liquid level meter used at present uses the conductivity of the measured object, converts the liquid level height change into the corresponding voltage pulse width change through the sensor measuring circuit, and the integrated control circuit processes the data and converts the data into the corresponding liquid level height to display or output the remote control signal. It is composed of partially or wholly insulated stick electrode, and tensioned or loosened cord electrode (if the container wall is conductive, the cord electrode can be replaced by the wall), when the liquid level rises or falls, the capacitance between the stick electrode and the cord electrode changes, and then the electric quantity (voltage value) of the instrument circuit system changes. And the current signal or the switching signal corresponding to the liquid level is output through the integrated control circuit. And according to the requirements of customers, the remote control or alarm of the automatic equipment is realized.
The temperature of the liquid in the container changes, so that the temperature of the electrode changes, the humidity and the temperature of the air in the container also change, the deviation of an actually measured capacitance value and a theoretical value is large due to the changes, the output voltage is influenced, the deviation of the output current and the actual value is large, the liquid level corresponding to the output current signal or the switch signal is inaccurate, and the error of the corresponding liquid level value is large.
In the case of a small temperature change, the actual liquid level deviation is not large. However, in the actual use process, the temperature difference is large (for example, the liquid temperature is repeatedly changed from 0 ℃ to 125 ℃), the output signal value cannot be accurately matched with the actual liquid level, and the control precision of the equipment is influenced.
SUMMERY OF THE UTILITY MODEL
The utility model discloses the technical problem of main solution provides a static capacitance level gauge with temperature self-interacting utilizes temperature sensor to detect sampling electrode temperature on every side, through AVR singlechip treater analysis processes, shifts the ware and give an instruction for the digit, does the correction compensation to output current or signal to reach output value and do not change along with the change of humidity, improve the measurement accuracy of actual liquid level, improve the life and the security of product.
In order to solve the technical problem, the utility model discloses a technical scheme be: provides a static capacitance liquid level meter with temperature self-regulation, which comprises a junction box, a collecting electrode, a connecting flange, a temperature sensor and a control chip, the junction box is arranged at the upper end of the connecting flange, the collecting electrode is vertically arranged at the lower end of the connecting flange and is connected with the control chip, the control chip is arranged in the junction box, a power supply, a capacitance frequency converter, an AVR singlechip processor, a capacitance sensor and a digital position changer are arranged on the control chip, the power supply is respectively connected with the capacitance sensor and the AVR singlechip processor, the capacitance sensor is connected with the AVR singlechip processor through the capacitance frequency converter, the AVR single chip processor is connected with the digital positioner, and the temperature sensor is arranged at the lower part in the collecting electrode and is respectively connected with the power supply and the AVR single chip processor.
In a preferred embodiment of the present invention, the power supply is a 24V dc power supply.
In a preferred embodiment of the present invention, the digital positioner is an AD8400 digital adjustable positioner.
In a preferred embodiment of the present invention, the digital shifter includes a positive compensation digital shifter and a negative compensation digital shifter.
In a preferred embodiment of the present invention, the temperature sensor is a DS18B20 temperature sensor or a DS78B20 temperature sensor.
In a preferred embodiment of the present invention, the signal of the temperature sensor is transmitted to the AVR single chip processor through a single wire interface.
In a preferred embodiment of the present invention, the AVR single chip processor is further connected to the current signal output terminal through a digital shifter.
In a preferred embodiment of the present invention, the current signal output terminal is connected to an external control device.
The utility model has the advantages that: the utility model discloses a static capacitance level gauge with temperature self-interacting utilizes temperature sensor to detect sampling electrode ambient temperature, through AVR singlechip treater analysis processes, gives the digit ware that shifts and gives the instruction, does the correction compensation to output current or signal to reach the output value and not change along with the change of humidity, improve the measurement accuracy of actual liquid level, improve the life and the security of product.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained without inventive work, wherein:
FIG. 1 is a schematic structural view of a preferred embodiment of the present invention of a static capacitance liquid level gauge with temperature self-regulation;
the labels in the figures are: 1. junction box, 2, collecting electrode, 3, connecting flange, 4, temperature sensor, 5, control chip, 51, power, 52, capacitance frequency converter, 53, AVR singlechip processor, 54, capacitance sensor, 55, digital displacement ware.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
As shown in fig. 1, the embodiment of the present invention includes:
a static capacitance liquid level meter with temperature self-regulation function comprises a junction box 1, a collecting electrode 2, a connecting flange 3, a temperature sensor 4 and a control chip 5, wherein the junction box 1 is arranged at the upper end of the connecting flange 3, the collecting electrode 2 is vertically arranged at the lower end of the connecting flange 3 and is connected with the control chip 5, the control chip 5 is arranged in the junction box 1, a power supply 51, a capacitance frequency converter 52, an AVR single chip microcomputer processor 53, a capacitance sensor 54 and a digital shifter 55 are arranged on the control chip 5, the power supply 51 is respectively connected with the capacitance sensor 54 and the AVR single chip microcomputer processor 53, the capacitance sensor 54 is connected with the AVR single chip microcomputer processor 53 through the capacitance frequency converter 52, the AVR single chip microcomputer processor 53 is connected with the digital shifter 55, the temperature sensor 4 is arranged at the lower part in the collecting electrode 2 and is respectively connected with the power supply 51 and the AVR single chip microcomputer processor 53 And (4) connecting.
In the above, the power supply 51 is a 24V dc power supply. The digital position shifter 55 adopts a digital adjustable position shifter with the model number of AD8400, wherein the digital position shifter 55 comprises a positive compensation digital position shifter and a negative compensation digital position shifter.
In this embodiment, the temperature sensor 4 is a DS18B20 temperature sensor or a DS78B20 temperature sensor. Wherein, the signal of the temperature sensor 4 is transmitted to the AVR single chip processor 53 through a single-wire interface.
Furthermore, the AVR single chip processor 53 is also connected to a current signal output terminal 56 through a digital shifter 55. Wherein the current signal output terminal 56 is connected with an external control device.
The concrete description is as follows:
(1) power supply: the 24VDC power supply is externally connected with a power supply and supplies power to the whole circuit;
(2) a capacitive sensor: providing a variable capacitance value for the circuit through the variation difference of the capacitance between the stick electrode and the rope electrode, wherein the variable capacitance value corresponds to the measured liquid level height one to one;
(3) capacitance-to-frequency converter: the filtering function ensures that the actual voltage and current output by adopting the capacitor are stable and reliable;
(4) AVR singlechip processor: and comparing and analyzing the sampled temperature and the reference temperature, and then sending an instruction to the digital adjustable positioner (AD 8400) for current value compensation. When the ambient temperature of the capacitive sensor rises, the capacitance value is reduced, the output signal current is increased, at the moment, negative compensation is adopted, and the resistance value of the IC5 positive compensation position changer in a schematic diagram is adjusted to reduce the signal current; when the ambient temperature of the capacitive sensor is reduced, the capacitance value is increased, the output signal current is reduced, positive compensation is adopted at the moment, and the resistance value of the IC4 positive compensation position changer in a schematic diagram is adjusted to increase the signal current, so that the accuracy of the output signal of the sensor is realized;
(5) DS78B20 temperature sensor: detecting the ambient temperature of the capacitance sensor, and transmitting a signal to the AVR single chip processor through a single-wire interface;
(6) AD8400 digital positioner: receiving an analysis instruction of an AVR singlechip processor, and performing positive compensation or negative compensation on the current of the temperature drift capacitor;
(7) and the current signal output is used as an output end, is connected with external control equipment and provides a control signal for the external control equipment.
Due to the inherent property of the capacitor (the temperature drift of the capacitor), the capacitance value of the sampling capacitor changes when the temperature changes, the temperature sensor is used for detecting the ambient temperature of the sampling electrode, the AVR singlechip processor is used for analyzing and processing the ambient temperature, an instruction is sent to the digital position changer, and correction compensation is carried out on the output current or the signal, so that the output value is not changed along with the change of the temperature, and the measurement precision of the actual liquid level is improved.
The utility model discloses a static capacitance level gauge with temperature self-interacting compares in prior art, has following advantage:
(1) the application range is expanded, and the liquid can be used under the liquid level of-40 ℃ to +200 ℃;
(2) because of the temperature compensation of the capacitor, the detection precision is greatly improved, and the deviation is reduced (from 3 percent to 0.2 percent);
(3) because the measurement is more accurate and stable, the service life and the safety of the product are improved.
The above only is the embodiment of the present invention, not limiting the patent scope of the present invention, all of which utilize the equivalent structure or equivalent flow transformation made by the content of the specification of the present invention, or directly or indirectly applied to other related technical fields, all included in the same way in the patent protection scope of the present invention.
Claims (8)
1. A static capacitance liquid level meter with temperature self-regulation is characterized by comprising a junction box, a collecting electrode, a connecting flange, a temperature sensor and a control chip, the junction box is arranged at the upper end of the connecting flange, the collecting electrode is vertically arranged at the lower end of the connecting flange and is connected with the control chip, the control chip is arranged in the junction box, a power supply, a capacitance frequency converter, an AVR singlechip processor, a capacitance sensor and a digital position changer are arranged on the control chip, the power supply is respectively connected with the capacitance sensor and the AVR singlechip processor, the capacitance sensor is connected with the AVR singlechip processor through the capacitance frequency converter, the AVR single chip processor is connected with the digital positioner, and the temperature sensor is arranged at the lower part in the collecting electrode and is respectively connected with the power supply and the AVR single chip processor.
2. The capacitance level gauge with temperature self-regulation of claim 1, wherein the power supply is 24V dc.
3. The capacitance level gauge with self temperature regulation as claimed in claim 1, wherein the digital positioner is a digital adjustable positioner model AD 8400.
4. The capacitance level gauge with temperature self-regulation of claim 3, wherein the digital displacer includes a positive compensation digital displacer and a negative compensation digital displacer.
5. The capacitance level gauge with self temperature regulation of claim 1, wherein the temperature sensor is a type DS18B20 temperature sensor or a type DS78B20 temperature sensor.
6. The static capacitance liquid level meter with temperature self-regulation function as claimed in claim 5, wherein the signal of the temperature sensor is transmitted to the AVR single chip processor through a single wire interface.
7. The static capacitance liquid level meter with the function of temperature self-regulation according to claim 1, wherein the AVR singlechip processor is further connected with the current signal output end through a digital positioner.
8. The capacitance level gauge with temperature self-regulation of claim 7, wherein the current signal output is connected to an external control device.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201921514115.7U CN210833767U (en) | 2019-09-12 | 2019-09-12 | Static capacitance liquid level meter with temperature self-regulation |
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| CN201921514115.7U CN210833767U (en) | 2019-09-12 | 2019-09-12 | Static capacitance liquid level meter with temperature self-regulation |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112525293A (en) * | 2020-12-04 | 2021-03-19 | 上海朝辉压力仪器有限公司 | Wireless 4G-based capacitive oil level sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112525293A (en) * | 2020-12-04 | 2021-03-19 | 上海朝辉压力仪器有限公司 | Wireless 4G-based capacitive oil level sensor |
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