Complete sensor data acquisition solution - industrial data acquisition system design Simulation technology -

Introduction of

programmable logic controller ( PLC） Is the core of many industrial automation and process control system, can monitor and control of complex system variables. Based on PLC system USES multiple sensors and actuators, can measure and control simulation process variables, such as pressure, temperature and flow rate. PLC is widely applied in many different applications, such as plant, oil refineries, medical equipment and aerospace systems, they need high accuracy, but also keep stable work long hours. In addition, required by the fierce market competition to reduce the cost and shorten the design time. Therefore, industrial equipment and key infrastructure design personnel to meet the customer to the accuracy, speed, noise, drift and the safety of strict requirements met severe challenge. Based on PLC application, for example, to explain how the highly integrated ADAS3022 multi-function and low cost by changing the analog front end ( AFE） Level, reduce the complexity and solve encountered in the design of multi-channel data acquisition system of many problems. With multiple input range, the high performance device is very suitable for high precision industry, instrument, power lines and medical applications, the data acquisition card can reduce the cost and speed up the product to market, and take up the space is small, easy to use, under 1 installed base rate to provide real precision of 16 bits.

PLC application example

figure 1 shows in the industrial automation and process control system using PLC to simplify signal chain. PLC controller usually includes analog and digital input/output ( I / O) Module, central processing unit ( CPU) And power management circuits.

in industrial applications, analog input module of remote access and monitoring of bad environment sensor signals, such as extreme temperature and humidity, vibration, chemical explosion environment. A typical signal including with 5 V, 10 V, & plusmn; 5 V and & plusmn; 10 V full scale range of single terminal voltage or difference voltage, mA or 0 to 20 mA, mA 4 to 20 mA, & plusmn; 20 mA range of the loop current. When confronted with serious electromagnetic interference ( EMI) The long cable, usually using current loop, because they have good noise immunity.

usually analog output module control actuators, such as relay, solenoid valve and valve and so on, to form a complete automation control system. They usually offer a 5 V, 10 V, & plusmn; 5 V and & plusmn; 10 V full scale range of output voltage, and mA 4 to 20 mA output of the loop current.

typical analog I/O modules including 2, 4, 8 or 16 channels. To meet the strict industry standard, these modules need to provide over-voltage, over-current and EMI surge protection. Most PLC including between ADC and CPU, CPU and DAC digital isolation. High-end PLC and possibly the international electrotechnical commission ( IEC） Standard channel segregation. A lot of I/O modules can be for each channel to single-ended or differential input range, bandwidth, and throughput single software programming.

in the modern PLC CPU automatically perform multiple control tasks, using real-time access to information for intelligent decision making. CPU may contain advanced software and Web connection, and the algorithm is used for error checking diagnosis and fault detection. Commonly used communication interface including RS - 232、RS- 485, industrial Ethernet, UART and SPI. Figure 1

. A typical PLC signal chain.

discrete data acquisition system solutions

industrial designers can use discrete components of high performance, or similar data acquisition system for PLC to build simulation module, as shown in figure 2. The main design considerations include input signal configuration, the overall system speed, precision and accuracy. The signal chain is shown here using ADG1208 / ADG1209 low leakage multiplexer, AD8251 fast instrument based programmable gain amplifier ( PGIA） , AD8475 high-speed funnel amplifier, 18 PulSAR® AD7982 differential input; The ADC and ADR4550 ultra low noise reference voltage source. This solution provides four different gain range, but in & plusmn; 10 V the maximum under the condition of the input signal, the designers must worry that multiplexer switching and settling time, and other analog signal disposal problems. In addition, under the 1 installed base rate achieve real 16 performance can be a serious challenge, even in these high-performance devices are used.

AD7982 has a full scale step 290 ns transient response performance. Therefore, to transform under 1 installed base rate at the same time guarantee the specified performance, PGIA and funnel amplifier must be set up in 710 ns time. However, AD8251 16-bit conversion accuracy is achieved for the 10 V step ( 0. 001%) The establishment of the time of 785 ns, so the signal chain to ensure maximum throughput will be less than 1.

in figure 2. Using the discrete element simulation input signal chain.

technology zone an area can produce two code conversion error interference to sharing of digital circuit design and simulation analytical static isolation technique can cause great harm to terminals and other electronic components of switching power supply design characteristics of the basic problem solving combinational circuits combinational logic circuit structure is introduced
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