【Daily Question 20090329】Popularizing knowledge of instruments

1. The “4C” technologies in Distributed Control Systems DCS refer to Computer, Communication, CRT, and Control. 2. The most common network topologies for DCS are star, bus, and ring. To improve its operational reliability, a redundant design is often employed; the main structural approaches include automatic backup systems based on redundancy and manual backup methods. 3.1 Determine the type of algorithmic function blocks based on the block diagram of the process control system ； 2 Specify the input and output signals for the functional block ； 3 Indicate the method of signal processing ； 4 Enter the parameters required by the function block, etc ； 4. The shielding layer should be grounded at one end and left ungrounded at the other; the grounding point can be located at the electronic device or at the sensing element, depending on the desired anti-interference effect. If both sides are grounded, the shielding layer forms a circuit with the ground, and common-mode interference signals can enter the electronic device through the distributed capacitance between the wires and the shielding layer, causing interference. However, if one end is grounded so that it is at the same potential as only one side, while the shielding layer still forms a circuit with the ground, no interference signals can enter the electronic device, thereby preventing the intrusion of common-mode interference voltages from the ground. 5. It means that the connection between the field transmitter and the instruments in the control room consists of only two wires, which serve both as power lines and signal lines. Compared to the four-wire system, its advantages are: it saves a large amount of cable and installation costs, and it is beneficial for safety and explosion prevention.

1. The “4C” technology in Distributed Control Systems DCS refers to Computer, Communication, CRT, and Control. 2. The network topologies of DCS mainly include five types: star, bus, ring, tree, and point-to-point interconnection ； To improve its operational reliability, redundant fault-tolerant design is often employed. Since the tasks performed by each computer in the system are relatively simple, dedicated computers with specific architectures and software can be used for the functions that need to be carried out, thereby enhancing the reliability of each computer in the system as well. 3. The main contents of DCS configuration include hardware registration, establishment of registrations, I/O channel registration, display configuration, graphic generation, control function configuration, trend curve registration, report generation, etc. 4. Shield grounding can eliminate the interference encountered during the transmission of signals on-site, thereby improving signal accuracy. The shielding layer of the signal cables in the DCS system should be grounded for shielding. The cable shielding layer must be grounded at one end to prevent the formation of a closed circuit that could cause interference. The metal shield of armored cables should not be used as a shielding protection ground; it must be grounded through a copper mesh or an aluminum-plated shielding layer. Connected to a common ground electrode. 5. It means that the connection between the field transmitter and the instruments in the control room consists of only two wires. In the two-wire transmission method, the power supply, the load resistor, and the transmitter are connected in series; thus, these two wires transmit both the power required by the transmitter and the output current signal. The two-wire system has 6 major advantages: (1) It is less affected by parasitic thermocouples, resistance drops along the wires, and temperature drift, and can use much cheaper, thinner twisted-pair wires ； (2) When the output resistance of the current source is large enough, the voltage induced in the wire loop through magnetic field coupling has no significant effect, as the current caused by interference sources is minimal; in most cases, using twisted pairs can reduce such interference ； (3) Capacitive interference can cause errors related to the receiver resistance. For a 4–20mA two-wire loop, the receiver resistance is typically 250Ω (with a sampled Uout of 1–5V). This resistance is low enough not to cause significant errors; therefore, the allowable length of wires is greater than that in voltage telemetry systems ； (4) Each individual reading or recording device can be connected to different channels with wires of varying lengths, without accuracy differences arising from such length variations ； (5) Using 4mA as the zero level makes it very convenient to determine whether the transmission line is open or the sensor is damaged (0mA condition) ； (6) It is easy to install surge protection and lightning protection devices at the dual-output ports, which contributes to safe lightning and explosion protection. This post was last edited by czx000323 on 2009-3-29 10:40.]

1. Answer: CONTROL technology, COMPUTER technology, COMMUNICATION technology, CRT technology. 2. Answer: The most common network topologies for DCS are star, bus, and ring. To improve operational reliability, redundant structures are often employed, with the main structural approaches including automatic backup systems based on redundancy and manual backup methods. 3. Answer: It includes the following aspects: 1 Determine the type of algorithmic function blocks based on the block diagram of the process control system ； 2 Specify the input and output signals for the functional block ； 3 Indicate the method of signal processing ； 4 Enter the parameters required by the function block, etc ； 4. Answer: What are the requirements for grounding the shielding layer of shielded wires (or shielded cables)? Why? Answer: The shielding layer should be grounded at one end and left ungrounded at the other; the point of grounding can be located at the electronic device or at the sensing element, depending on the desired anti-interference effect. If both sides are grounded, the shielding layer forms a circuit with the ground, and common-mode interference signals can enter the electronic device through the distributed capacitance between the wires and the shielding layer, causing interference. However, if one end is grounded so that it is at the same potential as only one side, while the shielding layer still forms a circuit with the ground, no interference signals can enter the electronic device, thereby preventing the intrusion of common-mode interference voltages from the ground. 5. Answer: It refers to the situation where the connection between the field transmitter and the instruments in the control room consists of only two wires, which serve both as power lines and signal lines. Compared to the four-wire system, its advantages are: it saves a large amount of cable and installation costs, and it is beneficial for safety and explosion prevention.

1: Computers. Communication, display, control: 2. Star, bus, ring; 3. Database editing, control table editing, diagram editing, controller and server editing, report editing, as well as deployment to engineers; 4. Shielded grounding can eliminate the interference encountered during the transmission of field signals, thereby improving signal accuracy. The shielding layer of the signal cables in the DCS system should be grounded for shielding. The cable shielding layer must be grounded at one end to prevent the formation of a closed circuit that could cause interference. 5: The two-wire system is considered in comparison to the four-wire system; in this setup, both the signal and the power supply are transmitted over two wires. Advantage: It simplifies wiring, but it can only be used when the sensor has low power consumption. If the sensor consumes a lot of power (such as in ultrasonic level sensors), a two-wire system cannot be used; instead, a four-wire system is required, with two wires for the power supply and two wires for the output.

1. What does the “4C” technology in a Distributed Control System DCS refer to? Answer: CONTROL technology, COMPUTER technology, COMMUNICATION technology, CRT technology. 2. What are the most common network topologies used in DCS, and which structural approaches are adopted to improve the reliability of the system? Answer: The most common network topologies for DCS are star, bus, and ring. To improve operational reliability, redundant structures are often employed, with the main structural approaches including automatic backup systems based on redundancy and manual backup methods. 3. What does the configuration of control software generally include? Answer: It includes the following aspects: 1 Determine the type of algorithmic function blocks based on the block diagram of the process control system ； 2 Specify the input and output signals for the functional block ； 3 Indicate the method of signal processing ； 4. Fill in the parameters required for the function block, etc. 4. What are the requirements regarding the grounding of the shielding layer of shielded wires (or shielded cables)? Why? Answer: The shielding layer should be grounded at one end and left ungrounded at the other; the point of grounding can be located at the electronic device or at the sensing element, depending on the desired anti-interference effect. If both sides are grounded, the shielding layer forms a circuit with the ground, and common-mode interference signals can enter the electronic device through the distributed capacitance between the wires and the shielding layer, causing interference. However, if one end is grounded so that it is at the same potential as only one side, while the shielding layer still forms a circuit with the ground, no interference signals can enter the electronic device, thereby preventing the intrusion of common-mode interference voltages from the ground. 5. Two-wire system? What are the advantages of two-wire systems? Answer: It refers to the situation where the connection between the field transmitter and the instruments in the control room consists of only two wires, which serve both as power lines and signal lines. Compared to the four-wire system, its advantages are: it saves a large amount of cable and installation costs, and it is beneficial for safety and explosion prevention.

1: Computers. Communication, Display, Control – in English these are Computer, Communication, CRT, and Control. Since the first letter of each term is C, it is abbreviated as 4C. 2: Star topology, bus topology, ring topology. 3: Editing databases, controlling table edits, editing graphics, editing controllers and servers, editing reports, as well as deploying software to engineers. 4: Shielded grounding can eliminate the interference encountered during the transmission of signals from the field, thereby improving signal accuracy. The shielding layer of the signal cables in the DCS system should be grounded for shielding. The cable shielding layer must be grounded at one end to prevent the formation of a closed circuit that could cause interference. 5: The two-wire system is considered in comparison to the four-wire system; in this setup, both the signal and the power supply are transmitted over two wires. Advantage: It simplifies wiring, but it can only be used when the sensor has low power consumption. If the sensor consumes a lot of power (such as in ultrasonic level sensors), a two-wire system cannot be used; instead, a four-wire system is required, with two wires for the power supply and two wires for the output.

1. What does the “4C” technology in a Distributed Control System DCS refer to? Control technology (CONTROL), computer technology (COMPUTER), communication technology (COMMUNICATION), image display technology (CRT). 2. What are the most commonly used network topologies for DCS, and which topological configurations are employed to improve system reliability? The most commonly used network topologies for DCS are star, bus, and ring. To improve operational reliability, redundant structures are often employed, with the main structural approaches including automatic backup systems based on redundancy and manual backup methods. 3. What does the configuration of control software generally include? 1 Determine the type of algorithmic function blocks based on the block diagram of the process control system; 2 Specify the input and output signals for each function block; 3 Indicate how the signals are processed; 4 Fill in the parameters required by the function blocks, etc. 4. What are the requirements for grounding the shielding layer of shielded wires (or shielded cables)? Why? The shielding layer should be grounded at one end and left ungrounded at the other; the point of grounding can be located at the electronic device or at the sensing element, depending on the desired anti-interference effect. If both sides are grounded, the shielding layer forms a circuit with the ground, and common-mode interference signals can enter the electronic device through the distributed capacitance between the wires and the shielding layer, causing interference. However, if one end is grounded so that it is at the same potential as only one side, while the shielding layer still forms a circuit with the ground, no interference signals can enter the electronic device, thereby preventing the intrusion of common-mode interference voltages from the ground. 5. Two-wire system? What are the advantages of two-wire systems? It refers to the situation where the connection between the field transmitter and the instruments in the control room consists of only two wires, which serve both as power lines and signal lines. Compared to the four-wire system, its advantages are: it saves a large amount of cable and installation costs, and it is beneficial for safety and explosion prevention.

1.4C refers to computer technology, communication technology, CRT technology, and control technology. 2. The most common network topologies for DCS are star, bus, and ring; to enhance its operational reliability, redundant structures are often used, with the main configurations including automatic backup systems based on multiple units and manual backup methods. 3. Control software configuration generally includes: 1. Determining the types of algorithmic function blocks based on the block diagram of the process control system. 2. Specify the input and output signals for the function block. 3. Indicate the method of signal processing. 4. Enter the parameters required for the function block, etc. 4. The shielding layer should be grounded at one end and left ungrounded at the other; the grounding point can be located at the electronic device or at the sensing element, depending on the desired anti-interference effect. If both sides are grounded, the shielding layer forms a circuit with the ground, and common-mode interference signals can enter the electronic device through the distributed capacitance between the wires and the shielding layer, causing interference. However, if one end is grounded so that it is at the same potential as only one side, while the shielding layer still forms a circuit with the ground, no interference signals can enter the electronic device, thereby preventing the intrusion of common-mode interference voltages from the ground. 5. In the two-wire system, the two wires serve both as power lines and as signal lines. Compared to the four-wire system, it reduces cable and installation costs, and enhances safety and explosion protection

1. What does the “4C” technology in a Distributed Control System DCS refer to? Answer: The “4C” technology refers to control technology (CONTROL), computer technology (COMPUTER), communication technology (COMMUNICATION), and image display technology (CRT). 2. What are the most commonly used network topologies for DCS, and which topological configurations are employed to improve system reliability? Answer: The most common network topologies for DCS are star, bus, and ring. To improve operational reliability, redundant structures are often employed, with the main structural approaches including automatic backup systems based on redundancy and manual backup methods. 3. What does the configuration of control software generally include? Answer: It includes the following aspects: 1 Determine the type of algorithmic function blocks based on the block diagram of the process control system ； 2 Specify the input and output signals for the functional block ； 3 Indicate the method of signal processing ； 4 Fill in the parameters required by the function block, etc. 4. What are the requirements for grounding the shielding layer of shielded wires (or shielded cables)? Why? Answer: The shielding layer should be grounded at one end and left ungrounded at the other; the point of grounding can be located at the electronic device or at the sensing element, depending on the desired anti-interference effect. If both sides are grounded, the shielding layer forms a circuit with the ground, and common-mode interference signals can enter the electronic device through the distributed capacitance between the wires and the shielding layer, causing interference. However, if one end is grounded so that it is at the same potential as only one side, while the shielding layer still forms a circuit with the ground, no interference signals can enter the electronic device, thereby preventing the intrusion of common-mode interference voltages from the ground. 5. Two-wire system? What are the advantages of two-wire systems? Answer: It refers to the situation where the connection between the field transmitter and the instruments in the control room consists of only two wires, which serve both as power lines and signal lines. Compared to the four-wire system, its advantages are: it saves a large amount of cable and installation costs, and it is beneficial for safety and explosion prevention.