ADAM-455 provides 8 channels of digital input and 8 channels of isolated digital output. Input receives 1~5 V voltage, and output provides 5~4 VDC open sampling < P > I, DA&; What are the general forms of C system? What are their advantages? What is the future trend?
roughly speaking, da&; C can be formed in three forms:
(1) sequential logic control system based on PLC.
(2) large-scale control system based on DCS
(3) DA& based on PC; System C.
advantages and disadvantages are shown in the table below.
compared with the project
PLC
DCS
PC-BASED
real-time performance
is high. It can be used in strict occasions, such as boilers, elevators, locomotives, etc. It can be used in large-scale strict occasions, such as chemical industry, steel, petroleum and other occasions
.
price
is
high
low
openness
poor. Belong to the exclusive system
. Belong to the exclusive system
.
ease of use
medium
poor
good.
poor computing ability
poor
strong
poor communication ability
poor
strong
development cost
medium
high
low
With the rapid development of PC and network technology, the future trend is that PLC and DCS will gradually move to PC. At the same time, PC-BASED gradually infiltrated into PLC and DCS, such as adopting soft PLC following IEC-1131. The three will learn from each other, that is, the openness and communication ability of PLC and DCS will be gradually strengthened, and the real-time performance of PC-BASED will be further improved.
second, why is the PC-BASED system open?
PC-BASED system adopts INTEL or compatible hardware and Microsoft or compatible software, commonly known as WINTEL architecture. WINTEL architecture has become the mainstream of commercial PC, and its standards, structure, software and development tools are open, so it has a good openness. And the hardware cost and the development cost are very low. Therefore, the PC-BASED da&; C architecture is welcomed by the majority of users.
third, DA& based on PC; There are several forms of C system
(1) Centralized data acquisition system based on board card. The basic way is to use data acquisition card to collect data. Representative manufacturers such as Advantech, NI and Geely. The main method is to insert a card based on IAS or PCI into an industrial computer or commercial machine (not strictly), lead the external signal to the terminal of the computer through wires, and then access the data acquisition card, which can be collected through customized software. Advantages are lower cost, and speed blocks, such as 1MHZ data acquisition, have disadvantages of average reliability and high wiring cost
(2) Based on distributed data acquisition system. The basic way is to adopt intelligent data acquisition module based on field bus, such as RS-485 (not strict), CAN BUS, Profibus and so on. Representative manufacturers such as ADVANTECH ADAM series. The basic method is to introduce the intelligent module into the computer through the field bus, and the upper computer communicates with the intelligent module through customized software. Advantages are easy maintenance, simple wiring and high reliability, while disadvantages are low sampling speed and high cost.
fourth, the classification of data acquisition card?
according to the types of collected signals: analog input and output, digital input and output, timing/counting, etc.
according to the sampling speed, it can be divided into high speed and low speed;
according to the isolation mode, it can be divided into isolated and non-isolated;
Therefore, users can choose the appropriate data acquisition card according to their own needs.
5. why is the analog input divided into single-ended and differential?
there are always various interference components in the signals from the site, especially * * * mode interference. The differential input of analog quantity is in the form of differential amplifier to eliminate the * * * mode interference of analog quantity. If the signal source is clean, single-ended input can be used. Two single-ended can form a differential input, so the input capacity of single-ended is twice that of double-ended.
VI. How to match the data acquisition card with the terminal
See the table for the matching of Yanhua data acquisition card with the terminal.
board
digital terminal board
analog terminal board
expansion terminal board
PCI-171
PCI-171hg
PCLD-871
PCI-1713
PCLD-881b
Adam-3981b. LD-88
ADAM-392
PCLD-782
PCLD-785
PCLD-885
PCLD-786
PCLD-7216
PCLD-88
PCLD-8115
ADAM-3937
PCLD-789D
PCLD-774+PCLD-779
PCLD- 788
PCL-818H
ADAM-392
PCLD-78
PCLD-88
PCLD-8115
PCLD-789D
PCLD-774+PCLD-779
PCLD-788
PCL-818HG
PCLD-8115
PCL-816
PCLD-88
ADAM-3937
PCLD-774+PCLD-789D
PCLD774+PCLD-779
PCLD-788
PCL-18
PCLD-88
ADAM-3937
PCLD-774+PCLD-789D
PCLD774+PCLD-779
PCLD-78 8
PCL-812PG
ADAM-392
PCLD-78
PCLD-88
PCLD-789D
PCLD-788
PCLD-779
PCL-711S
PCLD-7115
PCLD-789D
PCLD-788
PCLD-779
PCL-81 3B
PCLD-881
PCI-172
ADAM-3937
PCLD-88
PCL-726
PCLD-78
PCLD-88
ADAM-392
PCLD-782
PCLD-785
PCLD-885
PCLD-786
PCLD-7 216
PCLD-78
PCLD-88
ADAM-392
PCL-727
PCLD-88
ADAM-3937
PCL-728
ADAM-399
PCI-1751
ADAM-3968
ADAM-3968/ 5
PCL-72
PCLD-78
ADAM-392
PCLD-88
PCLD-782B
PCLD-785B
PCLD-786
PCLD-885
PCLD-7216
PCL-722
PCLD-7216
PCLD-782B
PCLD-785 B
PCLD-885
ADAM-395
PCL-724
PCLD-782B
PCLD-785B
PCLD-7216
PCLD-885
ADAM-395
PCLD-78
PCLD-88
ADAM-392
PCL-731
PCLD-782B
PCLD-785B
PCLD-7216
PCLD-885
ADAM-395
PCI-175
ADAM-3937
PCLD-88
PCL-73
PCLD-782
PCLD-785
PCLD-786
PCLD-885
PCLD-78
ADAM-392
ADAM-3937
PCLD-88
PCL-733
PCLD-88
ADAM-3937
PCL-734
PCLD-88
ADAM-3937
PCI-176
ADAM-3937
PCL-725
PCLD-88
AD Am-3937
PCL-735
PCLD-88
Adam-3937
PCL-833
Adam-3925
PCL-836
PCLD-88
Adam-3937.
generally, sending analog signals to the computer through the acquisition card is divided into three steps: (a) starting A/D; (b) A/D conversion; (c) The result of A/D conversion is sent to the computer. Step (c) can take different forms according to different data acquisition speeds.
the way of software query. Check the A/D completion mark by software and read the data into the computer. This method is suitable for low-speed occasions (<: 1KHZ)；
interrupt mode. After the A/D is completed, an interrupt request is sent to the PC, and the interrupt program collects data. This method is suitable for high-speed occasions (<: 3KHZ);
DMA mode. Use DMA controller to complete data transmission between data acquisition card and PC. This method is suitable for large-scale fast data transmission.
FIFO+INT。 In order to carry out high-speed data acquisition, A/D card should be provided with a first-in first-out (FIFO) buffer with a capacity of 1K or more. The data after A/D conversion is put into the FIFO first, and when the FIFO is half full, an interrupt signal is sent to the PC, and the interrupt service program reads the data. This method is suitable for high-speed data acquisition, such as >: 1KHZ data acquisition.
special high-speed data acquisition card. Such as a high-speed data acquisition card with embedded CPU on the card.
8. how to integrate the software and hardware of the data acquisition card?
General regular manufacturers will provide the following development tools along with the hardware:
Function library and routines under DOS
Register usage routines under DOS;
WINDOWS 16/32 BIT DLL；
VC/VB/Delpohi routine; (The above are generally provided free of charge);
OCX control (available for a fee);
OPC Server;
integration is achieved through configuration software. Generally, domestic configuration software supports board cards, such as Kingview
9. What are the advantages of adopting distributed data acquisition system?
among many PC-BASED manufacturers, Advantech's ADAM series distributed data acquisition system is the most representative.
1. classification and characteristics of fieldbus.
（1）CAN。 It was originally designed by Robert Bosch to provide serial communication of Electronic Control Units, ECUs) in vehicles. Its characteristics are real-time, high transmission reliability and data security. CAN products are extensive and low-cost, which goes beyond the automobile industry and is applied to industrial automation fields, such as mobile machine tools.
CAN is a message-oriented, multi-master and broadcast protocol, which is standardized as high-speed communication by ISO11898 (only the data link layer and some physical layers are defined). CAN adopts CSMA with non-destructive bit judgment or collision avoidance (CSMA/CA) to solve potential bus access conflicts without losing data and bandwidth. The length (judgment domain) of the identifier is 11-bit standard ID and 29-bit extended ID(CAN Kingdom).
(2)HART。 It is designed to realize the two-way digital communication between the intelligent field device and the main device in the process control application without interrupting the 4-2mA signal. It was originally developed by Rosemount and supported by the HART Communication Foundation (HCF). HART protocol conforms to layers 1, 2 and 7 of OSI-RM.
Bell 22 based on FSK technology is used in the physical layer. HART can run on the existing 4-2mA signal line in point-to-point mode, the process value is transmitted in analog mode, and HART is used for configuration and testing. Or run in multi-point configuration mode through twisted pair, when meeting the requirements of intrinsic safety, a single power supply can remotely supply up to 15 devices; If power is supplied locally, more devices can be connected.
(2) LonWorks
Lonworks is a peer-to-peer control network, which is suitable for connecting intelligent devices in distributed control and building automation, and was developed by Echelon Company of the United States.
LonWorks provides a variety of transmission media with flexible topology, and the transmission rate can reach 2.5Mbps. Decentralized contention for media access.
the application layer provides 36 services in 4 categories, and updates network variables (implicit messages) and explicit messages. The variable type is predefined or defined by C language. The message is sent in a point-to-point or multipoint manner, with or without acknowledgement.
(3) Modbus Plus
Modbus Plus is a local area network designed for industrial control applications (such as process control and monitoring information transmission) and developed by AEG Modicon.
the network bus adopts single/double cable layout, which can connect up to 64 addressable nodes with a transmission rate of 1Mbps. The information format is HDLC, and the media access is token.
(4) PROFIBUS: PROFIBUS
PROFIBUS is developed by Siemens, and * * * has