1.前言四端交流电桥通常用于低温测量,特别是使用锗温度计的情况。当既要求低功耗,又要求高准确度时,必须有良好的设计指标。最近,好几个厂家声称四端电桥测量功率等于或小于几个皮瓦。温度在1K 以下时必定要求这样低的测量功率。然而,对于高于1K 的测量,则允许电桥功耗大于传感器功率1nW,在40K 1. Introduction Four-terminal AC bridges are commonly used for cryogenic measurements, especially when germanium thermometers are used. When both low power and high accuracy are required, there must be good design specifications. Recently, several manufacturers claim that four-terminal bridges measure power equal to or less than a few pico-watts. Such a low measurement power must be required at temperatures below 1K. However, for measurements above 1K, the bridge power consumption is allowed to exceed 1 nW of sensor power at 40K