电阻型校验信号发生器设计要点.doc

摘 要 以Pt100为传感器的仪表中,通常采用电阻箱的方法对其校验,但电阻箱体积大，费用高，使用不便。本课题用 MOS 管组成可控电阻电路，并通过软件编程实现对电阻的控制。它具有数字化、可编程、结构简单等特点，很好的解决了上面的问题。 本课题所设计的是电阻型校验信号发生器。它的目的是产生50-200Ω的可变电阻，设计中，由键盘电路设定一个想要的电阻值，传输给单片机，经过内部处理后，由PWM电路完成D/A转换，去控制MOS 管组成的可控电阻电路，然后通过 ADC 将 MOS管两端的电压读入单片机，计算后得出实际的输出电阻，并由LCD显示出来。 本设计由软硬件两部分组成，硬件部分主要包括可控电阻电路、PWM电路、LCD电路等，并通过Protel 99SE软件完成电路原理图的绘制和PCB版的制作。软件部分，主要用C语言编程完成对D/A模块、键盘模块、PWM模块、LCD模块的控制，并验证性的编写了程序。 关键词：信号发生器；可控电阻信号；校验箱 Abstract In the instrument of Pt100 sensor, we often use the method of resistance box to check it. However, resistance box is bulky, expensive and inconvenient to use. This topic uses the MOS tube to compose the controllable resistance electric circuit and achieves to control resistance through software programming,it has many advantages. For example,digital, programmable, simple structure, etc. It is good to solve the over problem. The design of this topic is a resistance-type verify signal generator, its purpose is to generate 50-200Ω variable resistor. In this design,keyboard circuit sets a desired resistance value and gives it to the the single-chip,after processing in-house, completing the D/A converter by PWM circuit to control the controllable resistance electric circuit which is composed of MOS tube,the single-chip will read the voltage at both ends of MOS tube by ADC. It will get the output resistance after calculating ,the LCD will display it in the end . The design is mainly composed of hardware and software. Hardware includes the the controllabled resistance electric circuit, PWM electric circuit and LCD electric circuit, etc.Circuit schematic is drawed and PCB is produced by protel 99SE software. In the part of software, D/A module, keyboard module, PWM moduleand LCD module are controled by C language programming. The programme is compiled Confirmatorily. Keywords: Signal-generator;Controllable resistance signal;Verifying box 目 录 1 绪 论 1 1.1 课题的背景和意义 1 1.2 MSP430单片机的选型 1 1.3 可控电阻电路的概述 3 2 系统的硬件设计 5 2.1 系统的总体结构 5 2.2 可控电阻电路的设计 6 2.2.