摘要
温度是生产过程中常见和重要的物理参数。在日常生活和工业生产中，人们对温度测量的要求越来越高，主要表现在测量的精度、可靠性、稳定性等方面。温度的测量直接关系到产品的质量、生产效率以及生产安全等重大技术指标。同时，测温系统的成本和便携性也越来越受到人们的关注。传统的温度测量系统中，温度测量环节是由模拟温度传感器加上高性能的运放和A/D转换器构成，然后通过单片机进行控制，因而，所需的外围器件较多，硬件成本开销很大。基于片上可编程系统PSoC因在其芯片内部集成了丰富的模拟和数字模块，使一系列的控制任务大部分都可以在芯片内部完成，而且其可动态编程配置的功能，使其具有很高的灵活性，使得控制方便且生产成本比较低，所以在工业生产控制中得到了广泛的应用。本文设计了一种以Pt1000作为温度传感器，以可编程片上系统PSoC作为核心芯片，采用片内的模拟和数字IP核资源，利用Modbus协议进行上位机通信的温度测量系统。系统拟采用公司自主研发的温度采集器，集成为高密度温度采集系统，是针对高密度、高精度的监控，以及对于存在众多热电阻的场合设计的温度测量系统。
本文首先介绍了课题研究的背景和意义，并分析了当前温度测量技术和可编程片上系统PSoC的研究现状。以可编程片上系统芯片CY8C5868AXI-LP032作为系统核心，设计了硬件电路整体结构，系统分为四个子模块，温度采集模块、放大模块、A/D转换模块、通信模块。选取铂电阻Pt1000作为温度传感器，铂电阻采用三线制接法。温度信号输入电路采用独特的电桥电路测量技术，具有没有引线电阻影响，抗干扰能力强，电桥电路与测量电路完全隔离等优点。电桥电路中输出的模拟电压经过放大后，输入至AD转换器中变为数字信号，再由处理器换算出相应温度，在硬件电路设计中对各部分子电路进行了原理和功能的介绍，其中在对Δ-ΣADC配置时，根据系统要求对其分辨率、采样率进行相关参数配置。在系统硬件设计平台的基础上，使用PSoC Creator2.0集成开发环境进行了系统软件的设计，其中包括温度信号采集、AD值与温度值的转换、温度补偿、Modbus通信协议和信息帧格式等。设计中主要针对的是实际温度值获取、温度误差补偿的设计，其中采用的主要方法是分段线性化和线性标度变换相结合的方
法。为满足PSoC与计算机的通信加入了基于Modbus的通信协议，采用RS485接口标准来完成两者之间的数据发送和接收，在PSoC内部配置了全双工通信UART的各个参数，采用CRC循环冗余的校验方式。最后对系统进行调试，以测试工程的运行情况，首先使用PSoC的专用下载工具PSoC MiniProg对系统进行下载烧写接口调试，通过Visual Basic进行通信测试，然后通过电阻箱模拟铂电阻温度测试。最后对本文的的工作进行了总结，同时对其作出进一步展望。
关键词：温度检测；PSoC；
；通信PT1000 Modbus
Abstract
Temperature is a common and important physical parameter in the production proce.In daily life and industrial production, people have become increasingly demanding of temperature measurement, mainly performances in the measurement accuracy, reliability, stability and so on.Temperature measurement is directly related to the major technical indicators such as product quality, production efficiency production safety.In the meanwhile, more and more attention is paid to the cost and portability of the temperature measurement system.In Conventional temperature measuring system, the unit of temperature measurement is composed of analog temperature sensor, a high performance amplifier, A/D converter and controlled by the Single-Chip Microcomputer, Therefore, it not only needs more peripheral device, but also the hardware cost is expensive.PSoC programmable system on a chip have integrated so many analog and digital blocks that plenty of control tasks can be completed in the chip, and the capability of programming configured dynamically make it more flexible, because of controlled easily and relatively low production costs, so it is widely used in industrial production control.This paper designs a temperature measurement system with PSoC programmable system on chip as the core, which use Pt1000 as temperature sensor, make use of the analog and digital IP core resources and communication with the host computer adopting the modbus protocol.The design uses the collector temperature produced by their company, integrated as a measurement collector system of high density.It aims at a high density and high precision monitor, and can be applied to the condition with a number of thermal resistors.
First, this paper introduces the background and significance of the research, and analyzes the research status of the temperature measurement technology and the PSoC programmable system on chip.The hardware which uses the programmable system on chip-CY8C5868AXI-LP032 as the core of the system designs of the entire circuit configuration.There are four subsystems, including temperature acquisition module,
amplifier module, A/D converter module, communication module.Select the Pt1000 platinum resistance using three-wire connection as temperature sensors.The signal input uses a unique bridge circuit as measurement technology which has its advantages in anti-jamming capability, the impact of lead resistance, the bridge and measuring circuit isolated completely.Analog voltage from the bridge circuit is amplified and converted into digital signal, then acquire corresponding temperature through the proceor, and introduce the principle and function of each subsystem in the design of hardware circuit.According to system requirements, Δ-ΣADC is configured the relevant parameters, such as resolution, sampling rate.On the basis of the system hardware design platform, using PSoC Creator2.0 integrated software development environment for the design of the system, including the temperature signal acquisition, AD value and temperature value, temperature compensation, Modbus communication protocol and meage frame format.Design is mainly aimed at the actual temperature acquisition, temperature error compensation, the main method of which combines the piecewise and linear scale transformation.To meet the communication with the computer, the communication protocol based on Modbus is joined in PSoC, adapting RS485 interface standards to complete the sending and receiving data between the two, and configuring each parameter of UART of full-duplex communication inside the PSoC, using CRC cyclic redundancy check.Finally, the system is tested to check the operation of the project.Firstly, using the special download tools, PSoC MiniProg to debug the download programming interfaces, visual basic is for communication test, then the resistance box simulate platinum resistance temperature test.Finally, summarizing the work of this paper, at the same time, the further prospects are made.
Keywords: Temperature measure; PT1000;PSoC;Modbus communication
