低功耗解决方案地址传感器的激励要求

　　低功耗解决方案地址传感器的激励要求

　　有源传感器，需要激发产生可测量的输出，工程师可以把多种选择提供所需的电流或电压水平。从简单的基于运放的励磁电路到高度集成的多功能集成电路，可供选择的设备包括一系列设备，包括线性技术、微芯片技术和德克萨斯仪器等。

　　随着人们对物联网的兴趣越来越大，传感器子系统构成了许多预计将在薄膜电池和能量收集技术上运行多年的设计的核心。可靠的测量，但是，基于许多传感器的电阻，如热敏电阻、电阻温度检测器（RTD），应变计，和其他需要激发一个电流源或电压源产生的电输出。

　　An excitation current source output voltage of an RTD is directly proportional to the device‘s resistance. Although the use of high-excitation current would suggest larger voltage output， RTD resistance increases as its temperature rises from the higher current. Conversely， thermistor resistance drops as its temperature rises from similar self-heating effects. Beyond those types， other transducers such as Hall-Effect sensors， exhibit performance characteristics that vary significantly with applied excitation. As a result， active sensors typically require excitation maintained within strict limits to ensure reliable measurement with minimal nonlinearity.

　　Engineers can build simple excitation circuits using an available current-source IC， such as the Texas Instruments REF200， and a basic op amp， such as the TI OPA188 （Figure 1）。 With this approach， engineers can use two matched excitation sources produced by the current-source IC to adjust the op amp’s output voltage to zero at the low end of the desired sensor-measurement range.