传感器信号调理应用现场可编程模拟阵列.doc
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1、SENSOR SIGNAL CONDITIONING USING FIELD PROGRAMMABLE ANALOGUE ARRAYS (FPAA) 传感器信号调理应用现场可编程模拟阵列(FPAA) ABSTRACT Field Programmable Analogue Array (FPAA) is a new analogue design system. This paper introduces the application of FPAA in the signal conditioning of the temperature sensors. The major signal
2、 conditioning tasks undertaken are linearization, amplification and offset removal. Signal conditioning is very important for developing a sensor with good performance. Although there are many techniques for the signal conditioning, using FPAA has some significant advantages compared with the tradit
3、ional methods. In this paper, the design, simulation and measurement results of sensor conditioning circuit using the second-generation FPAA will be presented. The results obtained show that FPAA can provide an easy, convenient and reliable way for the signal conditioning of temperature sensor . 1 I
4、NTRODUCTION Sensors are widely used in process control, automation, data acquisition, test equipment, instrumentation and communication systems. All the sensors properties are influenced by temperature, dirt and other environmental parameters. Therefore some data processing circuits are usually inte
5、grated with the sensor units depending on the requirements. Sensor signal conditioning can be defined as the manipulation of the output signal of a sensor, probe or transducer including signal conversion, attenuating, amplifying, filtering and linearising. linearising 。 Signal conditioning of any an
6、alogue signal is required when the output signal is not up to the level or form in which it is required by the system. Previous techniques of sensor signal conditioning using discrete circuits have major disadvantages such as lack of precision due to component tolerances and mismatches; techniques d
7、eveloped did not support complex functions and signal conditioner developed was confined to the specific sensor and cannot be used for multiple sensors. The main challenge for the sensor signal conditioning is to develop a system that can easily modify the sensor output as required with good accurac
8、y and linearity. Using FPAA can achieve this purpose. FPAA introduces a radical software-centric approach to analogue circuit design where easy-of-use is a major feature. The technology has the econfiguration flexibility,allowing complete analogue signal conditioning/processing systems to be integra
9、ted using a Graphical User Interface (GUI). Because FPAA is programmable and reconfigurable, just one device can provide multiple sensor conditioning circuits under the real-time control of a digital microprocessor. Sensor signal linearisation, offset compensation, calibration, and signal modulation
10、 circuits can now be implemented in minutes on a drift-free integrated silicon platform. 2 SYSTEM DESIGN The system design challenges include sourcing stable references and stimulus; multiple sensors with differing signal conditioning needs, methods of calibration and maintenance and manufacturing c
11、onsiderations. FPAA can provide the sensor signal conditioning with an alternative solution. FPAA ,Design of the system using FPAA involves: (1) Amplification, offset removal and linearization of the signals from sensors; (2) Simulation using FPAA software before using the circuits for real time sys
12、tem; (3) Interfacing the Sensor system with the FPAA; (4)Carrying out test in order to condition the signal obtained from different Sensors. The FPAA was the heart of the whole system which takes the input signal that was initially converted from the physical signal by the sensors. The basic purpose
13、 of the system was to manipulate the sensor signal into a signal that was appropriate for any control system. The FPAAs that are used is Anadigms AN220E04 which is also called as “Dynamically Reconfigurable FPAA”. As the signal passes through the FPAA, the offset is firstly removed, and then the sig
14、nal is amplified and filtered. Thus by using the FPAA signal conditioning the sensor signal with higher precision can be achieved. Figure 1 System block diagram of FPAA sensor signal conditioning Figure 1 shows a system block diagram of FPAA sensor signal conditioning. The main features of the syste
15、m are: (1) Performance: The system should accept the voltage signal from the temperature sensor interfaced to the FPAA and process it accordingly depending on the specific feature selected among the different signal conditioning tasks. The system should convert the sensor output signal into a good q
16、uality signal that has been amplified, linearised and can be directly fed to a control system. The FPAA should also provide a predictable and a stable stimulation to the sensors interfaced to it.。 (2) Power supply: +5 volts. (3) Sensors: The sensors used for signal conditioning are two different typ
17、es of temperature sensors ,specifically thermistor based and thermocouple based temperature sensors. (4) Input: The input to the FPAA system is the signals obtained from the temperature sensors. The signals from the two different sensors are as follows: (a) Signal from thermocouple: The output signa
18、l from the thermocouple is a voltage signal that in turn corresponded to the change in temperature and is directly fed to the FPAA in addition with a couple of resistors to provide a common mode bias signal. (b) Signal from thermistor: The resistance obtained from the thermistor terminals correspond
19、s to the change in temperature. In order to convert the resistance obtained into a voltage signal a wheatstone bridge is constructed so that the signal can be fed to the FPAA and serve as the input signal to the FPAA. (5) Process: The process basically involved the conversion of the sensor signal to
20、 a level that could be directly connected to a control system. The whole process of signal conditioning involves offset removal, amplification, filtering and linearization. The design procedure for the system is as follows: (1) Design the circuits with required functions in FPAA using FPAA software
21、and various Configurable Analogue Modules (CAMs); (2) Simulate the designed circuits using FPAA software to view the performance of system; (3) Download the designed circuits to the FPAA development board, interface the sensor signal and test the real system. 3 SYSTEM IMPLEMENTATION The implementati
22、on of system involves the selection of the sensors and the design of the circuits in FPAA (AN220E04). 3.1 Selection of the sensors The first task involved in the implementation of the design is to find the suitable sensors that exhibit the characteristics required for interfacing it to the FPAA and
23、easily allow the successful signal conditioning using the FPAA. The sensor parameter that is particularly selected for signal conditioning is temperature. The next step for selecting the sensors is to select them from the different available categories. Thermocouple and thermistors are selected as t
24、he output signals from them need amplification and linearised. As can be seen, the purpose of the design can be easily defined and proved by using these two sensors. (1)Selection of thermocouple Thermocouples provide an economic means of measuring temperature with many practical advantages, they are
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- 传感器 信号 调理 应用 现场 可编程 模拟 阵列
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