新型薄膜热电变换器热电转换理论及制作工艺研究

The study on the alternating voltage and current criterion is very important because it is national standard measuring instruments in quantity transmission of alternating voltage and current, and it is the foundation of alternating power and electrical energy measuring. Many countries such as Germany, America, Japan have carried out the research on thin-film thermal converters, the key of the alternating voltage and current criterion, while it has not get the attention it deserves in our country. The project put forwards a novel high sensitivity thin-film thermal converter based on a microbridge resonator to measure the temperature of heat resistor non-contact with the hope of reducing AC/DC conversion errors and parasitic capacitance between heat resistor and temperature sensors. Average temperature of microbridge is rised due to thermal radiation of heat resistors. Axial compress stress increases(or tensile stress decrease) and the resonance frequency decreases with the temperature elevation. we can get information of the heat resistor's temperature by measuring the changes of the resonance frequency. This novel thin-film thermal converter have the adentages of high measuring sensitivity and precision, low AC/DC converting errors caused by thermoelectric effect, parasitic capacitance and dielectric loss. Heat absorbed by temperature measuring element in the novel thermal converter is negligible. Its output signal is frequency with negligible circuit noise, thereby it is expected to get an excellent thermoelectric converter with very high conversion accuracy.

交流电压(流)基准是国家交流电压(流)量值传递中的基准计量器具，也是交流功率和电能测量的基础，具有重要的研究意义和应用价值。德国、美国、日本等国家相继开展了交流电压(流)基准的核心部分-薄膜热电变换器的研制，而在我国尚未得到应有的重视。本课题以探索薄膜热电变换器中加热电阻温度的高灵敏度检测方式、减小温度传感器与加热电阻之间的寄生电容、最终减小交直流转换误差为出发点，提出采用微桥谐振器非接触式测量加热电阻温度。加热电阻辐射的热量使得微机械桥平均温度上升，轴向压应力增加(或拉应力减小)，谐振频率减小，通过测量微桥谐振频率的变化获得加热器的温度信息。这种新型薄膜热电变换器具有较高的测温灵敏度，可减小因热电效应、寄生电容和介质损耗引起的交直流转换误差；温度测量元件从加热电阻汲取的热量极小；其输出量为频率信号，受电路噪声影响很小，因此可望实现高计量精度薄膜热电转换器。

电流、电压、电功率这些基本电学量的单位和测量标准通过一系列的机械和电子标准单元和标准电阻器确定下来。热而，长期以来，人们知道但并没有充分认识到，对交流电量的测量需要借助基本的转换设备。而且在理想条件下，该转换设备对等量的交流量和直流量具有等量的响应，这就是所谓热电转换器。作为交流-直流转换标准的热电转换器是精确测量交流电量的核心器件，热电转换器通常包含一个或多个与电热器热接触或与电热器集成的热结（thermojunction），并通过热电激励在这些热结输出端子产生热电势，该热电势作为精确度量输入电热器电功率的量。这种热电转换器应具有长时间转换测量稳定性，无漂移，受温度影响极小，低损耗，频率特性好。 .本项目重点讨论限制转换精度的一系列因素。并从理论和实验两个方面研究这些限制因素对转换精度的影响，通过适当的近似方法，如非线性微分方程求解法，计算电流流过导电体产生的热量来消除影响热电转换精度的因素。本项目着重研究基于半导体微细加工工艺制作薄膜型热电变换器，包括器件设计、制作工艺和转换精度测量以及标定方法；还研究能精确测量半导体薄膜热电变换器转换精度关键数据的测量系统和设备，给出研制器件的重要测量数据。热电转换器及相关设备是音频范围内精确测量交流电流、交流电压和交流电功率的交-直流转换标准器具。该频段从25Hz到20000Hz，可以转换的交流电流从1mA 到50A，交流电压从0.2V到750V，转换精度可达0.01%。本项目研究内容是交流电功率和电能量测量的基础，具有重要的科学意义和应用价值。