In the water level control, the diffused silicon pressure transmitter can convert the water level signal into a pressure signal to achieve indirect measurement of the parameters. The configuration monitoring technology provides a basic platform for implementing data acquisition, process monitoring, and production control. It can form complex application systems with detection components and control components. It can save energy, improve measurement accuracy, improve product quality, and accurately transfer production between departments. Information and other aspects play a central role, which is conducive to enterprises to eliminate information islands, reduce operating costs, and improve production efficiency.
Diffused silicon pressure transmitter is composed of diffused silicon pressure chip and signal processing circuit. It has the characteristics of wide measuring range and high measuring precision through precise compensation technology and signal processing technology. It can detect pressure signal online for a long time. The diffused silicon pressure transmitter adopts 24V DC power supply. When the pressure is applied, the output voltage of the pressure chip will change, and then amplified by the signal processing circuit and converted into a standard 4~20mA linearly corresponding to the input pressure. The DC signal output can be directly connected with the secondary instrument and the computer control system to realize automatic detection and control of the production process, and can be widely applied to the detection of pressure in various industrial fields. Under normal circumstances, the diffusion silicon pressure transmitter measures the pressure signal, according to the pressure parameters and the water level.
Relationship between numbers: P=pgh
Where: P is the static pressure of the liquid in the container; p is the density of the liquid in the container, constant; g-gravity acceleration, constant; h-the water level of the liquid in the container. It can be seen from the above formula that there is a linear relationship between the water level parameter and the pressure parameter of the liquid in the container. Therefore, the diffused silicon pressure transmitter can be directly installed at the bottom of the water tank, and the water level signal can be obtained according to the measured pressure signal, thereby converting the water level measurement into the pressure measurement, thereby realizing the indirect measurement of the signal. The measured water level analog signal is converted into a 4~20mA DC signal by a pressure transmitter, and then converted into a DC 1~5V standard signal by a 250 resistor, and sent to a display instrument and a computer respectively.
The water level control system using the diffused silicon pressure transmitter as the water level detecting component is composed of two upper and lower liquid storage tanks. The water level measurement is completed by two CYG type diffusion silicon pressure transmitters installed at the bottom of the tank. The water level adjustment is realized by on-off control of the water pump, the regulating valve and the water outlet valve. The control requirements are: control the water level H of the water tank 1 to 1~8m, and control the water level H2 of the water tank 2 to 1~5m. Its control strategy is as follows:
a. Water tank 1 water level H1 ≥ 8m, turn off the water pump.
b. Water tank 1 water level H1 ≤ 1m, open the pump.
C. Water tank 2 water level H2 ≥ 5m, close the regulating valve.
d. Water tank 2 water level H2 ≤ 1m, open the regulating valve.
e. Water tank 2 water level H2 ≤ 1m, close the water outlet valve, otherwise open the water outlet valve.
2.1 Hardware part
The water level control system uses two CYG type diffusion silicon pressure transmitters installed at the bottom of the tank to detect the water level of the two water tanks in real time, and then converts the measured 1~5V standard signal into AD by the AD, according to the In the case of the collected signal, the computer outputs the control signal to the actuator through DA conversion, and performs the above control on the water pump, the regulating valve and the water outlet valve, thereby forming a computer-controlled closed-loop control scheme. Its system composition is shown in Figure 1.
In Figure 1, since the system has two analog inputs (A|) and three switches (DO), the l/O interface device uses the EVOC PCL-818L multi-function board. The card has 16 analog channels. Input, input analog voltage range -10~+10V, 1 analog output (maximum ±10V), 16 digital input (D) and 16 digital output (DO), TTUDTL level compatible. In order to facilitate the wiring between the object and the PCL-818 multi-function board, and at the same time select the corresponding terminal block, the DO channel uses 16-channel relay output terminal board PCLD-785, and the output contact load of the terminal board is DC: 30V/1A. AC: 120V/0.5A, fully meet the needs of pumps and solenoid valves. The A channel uses the PCLD-880 terminal block. The PCL-818L Multi-Function Board can be plugged into any spare |sA expansion slot in the computer case. The terminal block is mounted to fit outside the chassis. The PCL818L multi-function board and the AI terminal board PCLD-880 are connected by a 37-pin D-type plug, and the DO output terminal board PCLD-785 is connected by a 20-core flat cable, and the object and the terminal block are connected by wires. The 1/O allocation method is shown in Table 1.
The computer in the system selects the industrial control computer, and through the connected printer, the report output and curve display of the water level parameter can be realized. With the TCP/P protocol, computers can be interconnected with nternet or LAN for remote monitoring.
2.2 Software Section
The water level control system is based on hardware and is based on software. The composition of the hardware provides the system with the necessary conditions for connection with the computer; the design of the software makes full use of the characteristics of the computer and the role of the computer. The system design software uses the configuration software MCGS. The configuration software is a new type of software development technology that has emerged in the field of industrial automation in recent years. Developers usually do not need to compile specific instructions and codes, as long as they use the configuration software package. The tool can complete the development of the required application software through hardware configuration (hardware configuration), data configuration, graphic image configuration, etc. It has the advantages of simple secondary development, short development cycle, high versatility and high reliability. . According to the requirements of the automatic measurement and control system of the water level control system, after selecting the corresponding hardware equipment, the application software system configuration of the automatic measurement and control system can be configured by the McGS configuration software, that is, based on the MCGS industrial control configuration software. For secondary development, the specific configuration process is briefly described as follows:
1) System menu and system parameter configuration: In the “main control window” of MCGS, according to the requirements of the water level control system for the automatic measurement and control system, define and set its system menu and system parameters.
2) Configuration of equipment components: According to the hardware configuration in the automatic measurement and control system, set and configure the |/O card in the “Device Window” of MCGS.
3) Configuration of the user interface; according to the requirements of the water level control system and the user's habits, the MCGs tool is used in the MCGS "user window" to design and configure the system operation cover and the main control interface.
4) Configuration of real-time data objects: According to the requirements of this water level control system for its automatic measurement and control system, define and set related data and variables in the “real-time database window” of MCGS.
5) Configuration of the operation strategy: According to the operation requirements of the water level control system for the automatic measurement and control system, in the MCGS “Run Strategy” window, the “Startup Strategy”, “̈ Cycle Strategy”, “Alarm Strategy”, “ User policy", etc. are set and configured. After completing the above configuration settings, an automatic measurement and control application software system suitable for the water level control system can be generated, which can achieve water level measurement and display, water level control , water level alarm, report output, curve display and other functions.
From the practical application of the water level control system, it is feasible to use the diffusion silicon pressure transmitter as the water level detection component, combined with the configuration monitoring technology to form a complex application system, and also has many obvious advantages, such as flexible system configuration. Short development cycle, strong versatility and high reliability. It is believed that with the continuous improvement and development of the detection component technology and the industrial control configuration software technology, the combination of the two will be further developed and applied in more fields.