We can store electrical energy in to metal plates seperated by an insulating medium . we call such a device a capacitor , or a condenser , and its ability to store electrical energy capacitance . it is measured in farad 两片绝缘的金属板之间能够存储一定的电量，我们称这种装置为电容器，它的功能就是具有一定的电容量，其衡量单位是法拉。
Mems ( micro electromechanical system ) has become one of the most rapidly development technologies . along with the rapid development of mems techniques , capacitive sensor is used widely whose capacitance changes small , which has put forward the new request to the measurement technique . the common measure for capacitance measurement is that convert capacitance to voltage , electric current or frequency . the area of polar plate of the capacitor becomes smaller and smaller , and the total capacitance of micro capacitive sensor is usually several pico farad only . as a result , its change amount is smaller Mems ( microelectromechanicalsystem )近年来发展最快的技术之一,随着mems技术的快速发展,电容式加速度计的电容变化变化量越来越小,对检测技术提出了新的要求。在电容式传感器中,常用电容检测电路是将其转换为电压、电流或者频率信号。目前的微型电容传感器的极板面积变得越来越小,电容总量只有几个pf ,变化量就更小。
Sem and tem analysis show that the sample co - doped by nickel and titanium has nano - pellets with morpha like snow and great surface , which the initial discharge capacities in organic electrolyte reached 155 . 8mah / g and which were more than theoretic one farad electron discharge capacities ( 148mah / g ) . during the charging and discharging cycle , the change rate of the crystal volume was only 0 . 233 % and the sample showed long cycle life 样品在有机电解液的初始电容量( 155 . 8mah / g )大于理论1f电子放电容量( 148mah / g ) ，通过充放电前后xrd衍射图显示，放电前后晶胞体积变化仅为0 . 233 ，样品循环性能好。
Eddy current nondestructive testing ( ecndt ) is widely used to detect the thinness and defects of the sample , because of its characteristics of non - contact , high sensitivity and ease of detection . the principle of ecndt is that : when a probe coil with the ac exciting source is put near a sample , eddy current will be produced in the sample which will conversely affect the impedance of the coil according to the farad theorem . any un - uniformity in the sample will change the impedance of the coil and the output voltage 涡流无损检测技术具有灵敏度高、检测速度快、非接触等特点广泛应用于厚度检测和缺陷探伤，它的原理是当载有交变电流的检测线圈靠近金属导体时在导体中产生涡流，该涡流又影响原磁场，使得线圈的阻抗和感应电压发生变化，通过分析阻抗或感应电压的变化来获得被测导体的信息。
