ABB SC520 3BSE003816R1 Input function block, analog output function block

Description

SC520 3BSE003816R1  is to realize the difference between process variable (PV) and set value (SP) to carry out proportional-integral-differential operation, its parameters have set, process variable, proportional-integral-differential coefficient. Its output is usually sent to the address of the terminal board of the output board. Finally the output is sent to the valve. In general, the PID function block includes PV-SP operations. Some PID function blocks do not have SP and PV subtraction operations, so that other operations can be added before PID. Such as adding a dead zone. Another important function block in the function block library is the station function block, which can not use mathematical formulas to express the direct relationship between input and output, it is the function block to achieve man-machine communication, send the setpoint value determined by the human to the control loop, and send the conditions of when the control loop access and realize the conditions of hand/automatic switching.
Some DCS PID functional block is almost all-encompassing, with more than 100 parameters. 1, first ask where PV comes from, to fill in the PV address; PV value from an analog input module or terminal board; 2, the address of SP, SP address is usually the address of the station; 3, there is no dead zone, there is no dead zone, this item is not needed, there is a dead zone, to write the width and height of the dead zone; 4, do you want to integrate, do you want to integrate, what is the integral constant, 5, do you want to differentiate, do you want to differentiate, what is the differential constant; 6, what is the ratio; 7, do not want to die zone, if so, you need to enter the width of the dead zone, dead zone height. 8, whether you want to estimate Smith, if so, you should fill in the parameters of Smith’s estimator; 9, the output of the PID function block to there, such as the output to the analog output module or the function block of the terminal board. Its output is really to the valve. Output can also be sent to memory, but an address must be specified. At this time, the output of the PID function block becomes the input of another function block. Such as cascade control, the output of the first PID is the setting of the second PID, then there are two PV, also with two station function blocks, but only one station function block has a hand/self-switching relationship. The operator station and the operator station communicate with the function block directly, and the priority of the operator station is higher than that of the operator station.
Arithmetic operation addition, subtraction, multiplication, division, square, root and other DCS is essential. The second is function operation, trigonometric geometry operation, matrix operation, C language interface and Basic language interface function block. Function blocks connected with hardware, such as function blocks reading analog and switching inputs, function blocks reading analog and switching outputs from the network, function blocks reading analog and switching quantities, and function blocks sending analog and switching quantities to the network.
As a DCS controller, the functional blocks that must be possessed are: the functional blocks connected with the hardware are usually 4, which is related to the type of the input board; It includes analog input function block, analog output function block, switching input function block and switching output function block. Each function block must be connected to a specific terminal board. If there is a signal to receive the fieldbus, it also needs a functional block to receive the fieldbus signal. There are also four functional blocks connected to the network. They are: analog network input, analog network output, switching network input, switching network output. This is followed by the PID function block, the station function block, and then the arithmetic operations (addition, subtraction, multiplication, division). Then there are the operations of functions (first filter, lead-lag, two-dimensional curve, etc.), trigonometric geometry (sine, cosine, tangent, cotangent, etc.) and three-dimensional matrix operations. Some advanced operations, such as fuzzy logic, model control, etc., can be more or less, but they are the criteria to judge the strength of DCS system function. As for the controlled object function of some industries, there must be some special hardware support, such as: the SOE function of the power plant, there must be a fast interrupt hardware input board.
In order to increase the number of I/O points of the controller and increase the distance from the controller to the field, the fieldbus can be connected to the controller, such as the lonworks bus, then the controller should have a function block connected to lonworks. Lonworks bus module has independent input and output board and operation board, in the operation board there are a few function blocks.