The sensor is the primary equipment in the automatic control system, which is directly linked to the measured object. Its role is to feel the changes in the measured parameters, and send out signals that correspond to it. In the selection of sensors generally have three requirements: high accuracy, high stability, high sensitivity.
1. Temperature sensors:
Building engineering in the application of the main contact temperature sensors, such as RTDs, thermocouples, PTC silicon sensors, etc., due to the temperature measurement element and the measured medium need to carry out a full exchange of heat, the measurement is often accompanied by a lag in time. Such as Pt1000 its resistance at 0 ℃ when the resistance of 1000 Ω, with the rise in temperature resistance decreases, the sensitivity is generally in 3 ~ 4 Ω / K, the response speed is generally in 15 ~ 30 seconds.
2. Pressure sensors: commonly used electrical pressure sensors, the measured pressure change is converted to resistance, inductance and other changes in electrical quantities, so as to realize the indirect measurement of pressure. Commonly used differential pressure switch, gauge pressure sensor, static pressure sensor.
3. flow sensor: commonly used is the electromagnetic flow meter, by Faraday's law of electromagnetic induction, in the magnetic field and cutting the magnetic line of motion in the conductor there will be induced electromotive force generated by this induced electromotive force and the volume of fluid flow is a linear relationship. If the transformation can also use ultrasonic flowmeter, easy to install and maintain.
4. Humidity sensor: used to measure the relative humidity of indoor air.
5. Liquid level sensor: used to control the upper limit and lower limit level of water tanks, pools and so on.
In the automatic control system, it accepts the control signal output from the controller and converts it into linear displacement or angular displacement to change the circulation cross-section area of the regulating valve, in order to control the inflow or outflow of the controlled process of the material or energy, so as to realize the automatic control of process parameters.
6. Damper actuator: used to control the damper installed in the new air, return air outlet, both for switching control, can also be open control. The actuator has a universal fixture, can be clamped directly on the valve drive shaft, with a manual reset knob, in case of failure can be manually adjusted. According to the size of the duct cross-section can choose different knob torque of the actuator.
7. Water pipe valve actuator: supporting the use of valves, there are two types of switching and regulating, switching the general caliber of the large, in the cold and hot station for the control of the system process piping opening and closing, switching between various conditions; regulating the flow is mainly used to control the flow of air-conditioning units, according to the controller's temperature and humidity set point to control the return flow of water and the flow of steam humidification, so that the temperature and humidity are maintained at the set point. In the air conditioning unit, the return water flow and steam humidification flow are controlled according to the temperature and humidity set value of the controller, so that the temperature and humidity are maintained at the set value. DDC is used to monitor and control the system of electromechanical equipment in the controller, it is a complete controller, there should be hardware and software, can complete the independent operation, not affected by the network or other controller failure. Depending on the number of different types of monitoring points to provide the control requirements and the number of controllers. Each DDC has 10-15% points of expansion or margin.
(1) The controller composition meets the following requirements:
A) Programmable DDC with 32-bit or 16-bit microprocessor
B) Ability to operate independently from the central control host or networked
C) Power supply module
D) Communication module
E) DDC has a LED display in the template for each digital input and output point. Display the real-time changing status of each digital input and output point. In case of power failure, the backup battery of DDC can keep the data in RAM for 60 days.
F) When the external power is resupplied, the DDC can automatically resume normal operation without manual intervention.
G) In the event of an abnormal loss of data stored in the DDC, the user can rewrite the data to the DDC controller through the field standard serial data interface and through network operation.
H) The DDC's operating and application programs are written in PPCL high-level language.
I) The DDC program can be written and modified either on the central station or through a portable machine.
J) The DDC can store its due program when the external power is cut off and the backup battery is lost.
K) The acquisition accuracy of the DDC matches the accuracy of the sensor.
L) Working environment: temperature 0 degrees to 50 degrees, relative humidity 0-90%
M) Power supply: AC220V, ±10%, 50HZ.
2) The DDC is equipped with the following functions:
Timed start-stop adaptive start/stop
Automatic amplitude control Demand prediction control
Event automatic control Scanning Program Control and Alarm Handling
Trend Logging Comprehensive Communication Capabilities In recent years, the building of the future has been thought to be filled with a wide variety of intelligent devices. Sensors, actuators, valves, etc. in the building control network are intelligent, and the building infrastructure can seamlessly connect the data network and control network to form a total building network. The overall building network will become the model for future building control. In the mid-nineties, people gradually formed a new concept of information transmission in building automation: intelligent devices - sensors, actuators to form an autonomous control environment, i.e., intelligent temperature sensors, light switches, curtains, elevator buttons, card readers and so on can be mixed as one work. Networks - The new generation of smart devices can seamlessly connect various networks such as the Internet, corporate networks or building wide area networks, local area networks, etc. Global Networking - With the development of networks, devices and systems, users can remotely access any point on the intelligent building network from anywhere in the world at any time. The concept of a holistic building network is no longer an aspiration for the future, it is happening today. The number of manufacturers offering intelligent devices, subsystems and systems is growing exponentially. The impetus is mainly coming from owners, who are demanding more and more integration in their buildings and properties, and justifiably so. Because today, building automation subsystems such as access control, CCTV, elevators, air conditioning, HVAC, security and fire protection in the intelligent products have been introduced. Although these many intelligent products are leading to the gradual renewal of building subsystems, but the real overall building network system is still rare. Manufacturers say they are moving toward open systems, but at the same time they are limiting the development of interoperable products because they fear the changes in the marketplace brought about by a standardized network communication protocol and a truly open architecture. Large companies are willing to maintain the status quo because they have a vested interest. Many of the major vendors adopted L0NWORKS technology for their underlying devices because they found that using the L0N WORKS platform was a cost-effective way to interoperate devices in their closed systems, but they were willing to go as far as they could. In the sixties and seventies, the computer industry was monopolized by giants such as IBM, Burroughs, Control Data, Sperry, NCR, and Honeywell, whose equipment was large, closed, and very expensive. In the seventies and eighties, a number of new computer companies came out such as: DEC, Data Geheral, Tande and Wangan Computer, these companies' computer products are more distributed but they are still expensive closed master-slave systems.
In the nineties another group of computer companies took over the leadership of the industry: Compaq, Dell, Gateway and Hewlett-Packard. These new companies were able to do so because their products were fully open, had a high price/performance ratio, and were flexible. As sales increase, manufacturers are better able to cut costs and expand their markets to make more money. Toward the development of today's building automation industry and yesterday's computer industry has much in common. The traditional building control system is also closed, usually purchased from a company and installed by them. Because these systems are master-slave control structures, installation and maintenance costs are high and there are limitations on future additions, deletions, modifications and repairs. Any integration at the subsystem level requires expensive gateway hardware and specialized editing programs. Unfortunately, many control system manufacturers are not willing to provide a truly open platform. End users want peer-to-peer open systems without expensive, proprietary, closed templates and central controllers with their complex wiring, control programs and maintenance. Today's control equipment manufacturers want to use their expensive gateways to do integration (to achieve interoperability), although these gateways can make the subsystem to achieve a certain degree of interoperability, but the gateway limits the communication between the end device, and makes the whole system complex. Intelligent routers solve these problems. Routers make channels transparent to each other, allowing access to an end device on a channel from anywhere. Routers increase system reliability and provide enough flexibility for upgrades, changes, and replacements. These routers work by providing logical rather than physical isolation in the network. When we as a control industry adopt a truly open system, owners and property managers will enjoy the true benefits of integrating a building management system from a variety of manufacturers: the freedom to choose the products, technologies and services with the highest price/performance ratios; and the costs can be amortized over the true life of the product. The companies involved in the development and installation of open control networks provide the basic system-level building blocks for open LONWORKS control networks, which are primarily intended for OEMs. Products are: development tools, Lon Talk (communication protocols), neuron chips, transceivers, network interfaces, network operating systems, network management software, these series of products can enable OEMs to directly access the benefits of the LONWORKS network without having to re-develop the core of the technology of the open control network, they can focus their valuable human and material resources in the development of the control devices and systems to improve their products. They can focus their valuable human and material resources on developing control equipment and systems, increasing the added value of their products and thus reducing development and production costs. Products for System Integrators The system integrator plays a key role in realizing a highly distributed, interoperable control solution. For this reason, Eche offers a suite of Lon Point system products for system integrators. These products allow system integrators to integrate L0NMARK products from different manufacturers to complete a complete control solution. This solution replaces the central controller described above and distributes the control algorithms directly to the I/O devices.
Echelon's Lon Point interface modules not only replace these centralized controllers, but also allow system integrators to connect legacy devices that do not have neuron chips and transceivers to the Lon Works network with Lon Point, which contains neuron chips that directly process signals from sensors and actuators. These easy-to-install, simple-to-program LonPoint modules offer a significant price advantage over complex centralized controllers, both in terms of price and in terms of wiring work and maintenance. echelon foresees that the company's vision in the field of building automation in general is to move the market towards LONMARK interoperability-based, open, fully distributed networked control systems. To do this, manufacturers are required to eliminate proprietary central controllers and gateways, reduce equipment, installation and lifecycle costs, and thus reduce system costs. A number of manufacturers are still skeptical about "open systems. They are concerned about the rapid growth of the market after opening. In fact, they are wrong. When the control field is opened up, the market will certainly expand rapidly and producers will then be able to achieve a real profit margin. the LONWORK Interoperability Association and its more than 240 members are working to promote a truly open building automation market. Members come from manufacturers, integrators, and owners and end users. The Association's work includes developing interoperability standards, certifying products, and promoting the market. In the construction industry, with the rapid growth of corporate data networks and the Internet, the need to connect corporate control networks to TCP/IP has become increasingly urgent. Routers instead of gateways to connect the different channels, this "tunnel" router principle of operation will L0N WORKS information packaged in TCP/IP packets, sent to the TCP/IP network. Because this type of system is an integrated network, all points are transparently connected, making the system very easy to install, monitor, diagnose, and maintain. In other words, a network tool can work on other nodes on the network from anywhere on the network.
The new generation of routers can transparently and seamlessly connect channels on the Quad NW0RKS network to the Ethernet backbone network, as well as directly to computers with Ethernet plug-in cards. The result is a powerful and coherent LONWORKS building automation system that connects the building property management software system to all intelligent nodes. This integrated network architecture dramatically reduces system life cycle costs and allows for solutions that are now considered impossible. In order to realize the application of this IP (Internet Protocol) connection method, the company is working closely with CISCO to develop and launch products to meet the needs of this market. Now a new generation of building automation products have been introduced to the market, SIEMENS, Honeywell, Johnson, Hysine and other companies are constantly seeking technological innovation and breakthroughs. Building systems are truly open, requiring owners, designers, integrators *** with manufacturers to demand truly open and interoperable new products. Without this push, controller manufacturers will continue to offer the same old products. The industry needs to set new standards, develop LONMARK interoperability, design peer-to-peer planar system architectures, and utilize gateway-less and LNS platform-based networking tools.