投影仪在课堂中使用广泛,但是在使用投影仪时,由于屏幕对亮度比较敏感,常常需要人为调整教室的灯光或开关窗帘.研究了一种基于单片机的智能控制系统,当投影仪幕布落下的时候,检测教室的光强,如光线较暗,适合投影仪的使用,则不采取动作;如光线较强,则关闭前排电灯并驱动步进电机拉上窗帘,使教室光线变暗.此控制系统可实现教室亮度和投影仪之间的智能联动,有效节省人力,提高上课效率.

With the consideration of fusion and mutualism,this paper summarizes some reform measures that are adopted in construction of the open experimental environment,such as the structure layout,the experiment contents,the construction of the teaching group,etc.The reform can further boost the sustainable development of the open experimental environment under mutual-benefit and win-win guidelines.

To learn circuit system＇s frequency characteristic Intuitively,Steady-state response measurements method is used to develop a kind of digital circuit system frequency characteristics analyzer.DSP is used as main controller to run the main program and do digital signal processing,FPGA is used to apply logic control function and integrated digital direct frequency synthesis chips is used to generate sine wave.The input signal and response of circuit under test is sampled by ADC module.The analyzer obtains the amplitude-frequency characteristics and phase-frequency characteristics after appropriate computing.Experiment show that this analyzer has friendly man-machine interface,measurement speed and the testing wave is consistent with the theoretical results.

As agriculture predators cause substantial damage to agricultural crops, an intelligent bio-acoustic frightening system has been designed against agriculture predators. In this system, the Wireless Sensor Networks (WSN) was used as communication and detection platform, and embedded system based on ARM9 MPU and AT89C51SND1 were used as hardware platform of the central-controller and the actuators. Agriculture predators were detected by the pyroelectric infrared sensor with its type determined according to the Crop types-Environment-Predator-Natural enemy model, then the actuator broadcasted the call of relative natural enemy to accomplish intelligent repelling against different agricultural predators. Compared with present repelling method which can be easily habituated by target predators, this system is more effective and covers lager area, and with better expansibility and flexibility. It is an intelligent and pollution-flee solution against agriculture predators.

The design research of full-bridge trigger set is made in the paper,including two kinds of chips:TCA785 and FP- GA.By means of the experiment results, it can be seen that the digital trigger technology is the main development trend in the fu- ture.

In order to improve experiment ability and cultivate creative talent,it's of importance that construction open experiment environment for students.This paper introduces establishing of open Lab of Electrical Instrument and Measurement,and taking measures,and receiving positive effect from practice.

A new virtual calibrator for instrument transformer is presented.A phase difference correction method is applicable to correct electronic instrument transformer.

本文介绍了清华大学非电专业"计算机硬件技术基础"课程在能力导向理念下的教学目标、教学内容、教学方法、成绩评定和教学效果,着重描述了"以学生为本、培养学生综合能力"的教学思想在各教学环节中的具体实施。

分析了在Rogowski线圈测量脉冲电流及电网短路电流时电路参数和线圈结构对测量准确度的影响,结果表明:用I1m＝nim算式计算脉冲电流幅值I1m时将产生一定误差;利用简化方程确定短路电流大小时同样会产生误差;若线圈均匀缠绕于骨架,其输出信号不受一次电流导体位置和导体倾斜度的影响.修订了脉冲电流及电力系统短路电流的表达式,并以线圈结构变化为例进行了测量误差估计.

本文从5位华裔科学家荣获诺贝尔奖的成功经历开篇,分层论述实验的重要性和面向21世纪实验室应具备的3种功能,指出高校要开展素质教育、培养创新人才和实验室工作必须改革.