控制与保护开关电器用4~20mA标准电流输出电路

Design of Low Cost 4~20 mA Standard Current Output Circuit for Control and Protective Switching Devices

提出了一种用于控制与保护开关电器的4~20 m A标准电流输出电路。阐述了基于脉宽调制技术实现数模转换的原理,在电路仿真的基础上设计了硬件电路,分析了电路的各个部分并详细讨论了实现脉宽调制输出的软件设计方法。对导致输出电流产生误差的因素作了进一步探讨,改进了相关器件选型,试验表明提高了电路精度和线性度。该电路抗干扰能力强、安全性高且比采用数模转换器实现方式的成本低,适合传输远程模拟量信号,可用于工业现场设备及自动化仪表的相关开发。

A 4 - 20 mA standard current output circuit for control and protective switching devices was proposed. This paper expounded the realization of digital to analog conversion based on pulse width modulation, designed the hardware circuit using the circuit simulation technology. It described the different parts of the circuit and discussed the software design method about pulse width modulation output. It further analyzed the factors causing the current output error, and improved the accuracy and linearity of the circuit by putting forward adjustments on device selection with the experiments. Compared to using digital to analog converter,the circuit has low cost. It also has a Strong anti-interference capability and high safety that is ideal for remote analog signal transmission. It can be used for the development of industrial field devices and automation instrumentation.