本文提出并演示了一种基于微波谐振原理的带有电阻消能结构的高精度液位传感器，在0~50 mm的量程范围内，分辨率可达微米级。微波谐振原理传感器第一反射点是传感器自带的固定点，第二反射点为液面，即为可变点，两反射点之间形成谐振腔结构。当液面的高度发生变化时，第二反射点发生移动，会导致两个反射点之间的距离发生变化，因此改变谐振腔长，通过测量谐振腔长的大小即可确定液位的变化量。同时，所加入的电阻在提高量程范围的基础上，还大幅提升了频谱质量和测量精度。实验结果表明，该液位传感器在0~50 mm的量程范围内具有1 μm数量级的分辨率和-1.927 2 mm/mm（谐振波长变化/液位）的灵敏度。该新型微波液位传感器具有机械鲁棒性强、易于制造、成本低和高分辨率等优点，有望应用于水利水电的量水堰监测等领域。
In this paper, a high-precision liquid level microwave sensor assisted with energy dissipation control is proposed and demonstrated. The sensor achieves a micrometer-level resolution within a measurement range of 0~50 mm. Built on microwave resonators, the sensor comprises an inner conductor, an outer conductor, a resonant cavity, and a resistor. The resonant cavity is constructed of two reflection surfaces, where the first is a fixed point located inside the sensor, and the second is the measured liquid level. When the liquid level changes, the second reflection point changes accordingly, introducing cavity length shift. The liquid level change can be determined by measuring the variation of the resonant cavity shift. Meanwhile, the added resistance not only extends the liquid level measurement range, but also improves the spectral quality and measurement accuracy. Experimental results show that the liquid level sensor reaches micron resolution and a sensitivity of -1.927 2 mm/mm (resonant wavelength change/liquid level) in the range of 0~50 mm. Due to its mechanical robustness, easy fabrication process, low cost and high measuring resolution, the proposed sensor can be applied in fields such as water conservancy and hydropower weir monitoring.
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