共查询到18条相似文献,搜索用时 329 毫秒
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介绍了一种测量微小电容的新方法.利用最新的电容数字转换(CDC)芯片AD7745,充分考虑小电容信号受导线电容及其他寄生电容的影响,设计了基于AD7745的信号检测电路,并通过单片机进行温度补偿.详细介绍了AD7745的初始化设置及数据使用方法. 相似文献
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具有50MHz时钟率的AD7008单片CMOS DDS调制器 总被引:2,自引:0,他引:2
AD7008是美国最新推出的单片CMOS DDS调制器,它把32 bit相位累加器、SIN/COS查找表、10 bit D/A变换器以及调制和控制电路集成到一起,集相位调制、频率调制、幅度调制及I/O正交调制等多种功能于一身,具有很高的性能价格比.AD7008的时钟速率可达50MHz,输出信号频率可达 20MHz,频率分辨率可达 0.02Hz.本文简要介绍了AD7008的原理、结构及使用方法. 相似文献
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设计了一种用于高速CMOS图像传感器的列并行标志冗余位(RSD)循环式模/数转换器(ADC)。该ADC在每次循环中采样和量化输入信号同步进行,速度比传统的循环式ADC提高了1倍。利用电容复用技术,对于像素输出信号的相关双采样(CDS)操作和精确乘2运算,将仅使用1个运放和4组电容来实现,减小了芯片面积。通过0.18μm标准CMOS工艺完成了ADC电路设计和仿真。SPICE仿真结果表明,在4 MS/s的采样速度和1.8 V电源电压下,ADC的SNDR达到55.61 dB,有效位数为8.94 bit,功耗为1.34 mW,满足10 bit精度高速CMOS图像传感器系统的应用要求。 相似文献
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AD7745是一种响应快速兼超低功耗的高精度电容数字转换器,其采用的通信总线I2C是一种简单双向的两线制同步串行总线,它只需要一根数据线和一根时钟线即可实现连接器件之间的数据传送,但目前广泛应用的51系列单片机均不具有这种接口;文章详细研究了AD7745芯片内部的测量原理及寄存器配置方式,设计了其与单片机的硬件连接电路,使用STC89C52RC单片机的两条普通I/O线,通过软件编程模拟I2C总线所要求的操作时序,实现了对AD7745的控制与数据读取;同时,给出了其中关键程序,调试结果证明了该系统的有效性与稳定性。 相似文献
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吴中华 《电子制作.电脑维护与应用》2009,(2)
对于11期的稳压电路,首先两个100μF电解电容的作用是不相同的,输入端的是滤波电容,因为经桥式整流后的输出是全波脉动电压,其交流基波电压的频率为100Hz,且幅度较大,电容的容抗为1/2πfC,故电容量越大容抗越小,对基波 相似文献
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A surface acoustic wave (SAW)-based high-voltage sensor is described. The sensor consists of a SAW oscillator fabricated on a 10 mm × 10 mm 128° rotated Y-cut, X-propagating LiNbO3 substrate. The voltage is applied to electrodes on the substrate, and the resulting electric field changes the propagation time of the SAW. The propagation time is directly related to the output frequency of the SAW oscillator. The high-voltage sensor offers a small-sized high-voltage measurement device with several attractive features: a high resolution (better than 0.2 V up to 2.4 kV, better than 0.4 V for higher voltages), a large range (−10 to +10 kV), a high input impedance (> 1013 ω) and a low input capacitance (< 10 pF). The sensitivity amounts to 16 Hz V−1. 相似文献
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A novel parametric-effect MEMS amplifier 总被引:2,自引:0,他引:2
Raskin J.-P. Brown A.R. Khuri-Yakub B. Rebeiz G.M. 《Journal of microelectromechanical systems》2000,9(4):528-537
This paper presents the theory and measurements of a mechanical parametric-effect amplifier with a 200-kHz input signal and a 1.84-MHz output signal. The device used is a MEMS time-varying capacitor which is composed of an array of low-stress metallized silicon-nitride diaphragms, and is pumped by a large-signal voltage at 1.64 MHz. This induces a large change in the capacitance, and results in parametric amplification of an input signal at 200 kHz. The parametric amplifier capacitance is 500 pF, resulting in an output impedance of 140 Ω. A higher impedance can also be achieved with a lower capacitance. To our knowledge, this device is the first-ever MEMS mechanical up-converter parametric-effect amplifier developed with an up-conversion ratio of 9:1. The measurements agree very well with theory, including the effect the series resistance and the and of the MEMS time-varying capacitor. The application areas are in amplifiers which operate at very high temperatures (200°C-600°C), under high particle bombardment (nuclear applications), in non-semiconductor-based amplification, and in low-noise systems, since parametric amplifiers do not suffer from thermal, shot, or 1/f noise problems 相似文献
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基于四相检测技术的微电容传感器 总被引:8,自引:4,他引:8
一种基于四相检测技术的电荷转移式微电容传感器,具有很强的消除杂散电容影响的能力,适用于被检测对象电容值小于1pF的场合,分辨力达1fF,灵敏度高于1V/pF,并能输出4~20mA的电流。其优良的性能和低廉的价格,使得微电容传感器的广泛推广应用成为可能。 相似文献
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This article describes a commercial quartz tuning fork (QTF), 8 mm in height by 3 mm in diameter, holding a two-terminal electronic component with a nominal frequency of 32.768 kHz and 12.5 pF typical load capacitance packed in a vacuum-sealed metal container, which has been used as a sensor for low-temperature measurement with good sensitivity, repeatability, and reliability. An embedded readout design with the support of a programmable system on-chip (PSoC) and virtual instrument control program, which uses a personal computer as an input/output device, provides online data acquisition of the QTF frequency data, which will in turn provide the measurement of the low-temperature bath in which the QTF is immersed. The embedded PSoC readout captures the varying frequency signals from the QTF as a response to the measurement temperature, processes it, and sends the frequency value to a personal computer, where LabVIEW, a graphical language ("G" language), displays the data in a graphical format. The QTFs for low temperature (300 K to 77 K) are well studied, whereas a sensor using a PSoC embedded design as a readout is a novel design implementation. 相似文献
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针对岩土工程对现场数据采集的精度和速度提出了更高的要求,该文以S3C44B0处理器为核心,辅以必要的外围电路,设计了一种上位机监控的多路数据采集器。采用ADS8505芯片进行AD数据采集,达到16位的精度;采用电子开关CD4067芯片扩展输入通道,实现了16路信号的数据采集;通过RS-485方式与PC机进行数据通信,实现上位机对采集器的控制和数据的处理显示,进而设计出了高精度、高分辨率、多通道的数据采集系统。 相似文献
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刘俞辰 《计算机测量与控制》2018,26(11):297-302
为解决如今市场电阻电容测量仪器精度低,成本高,操作繁杂等问题,提出了一种基于STC89C52的电阻电容智能测量方案,系统在电阻测量方面采用LTC1864高精度十六位ADC采集电压计算电阻值,仿真测量精度可达0.09%,通过单片机控制继电器实现电阻的量程自动转换;在电容测量方面使用NE555芯片分别与100,100k,10M电阻组成多谐振荡器,通过单片机计数器计算振荡频率,实现多档位电容的测量,量程5pF到500uF,仿真精度1%,电容设置pF、nF、uF三挡,使用简便。数值通过LCD1602进行显示,并显示对应的提示语句,当超出量程时,显示报警信息。实验结果表明该系统测量精度高,成本低,使用简便,实现了系统智能的设计要求,具有一定应用价值。 相似文献