Terahertz Systems Technology Group, Department of Electrical Engineering and Information Technology, Technische Universitat Darmstadt, Merckstr. 25, 64283 Darmstadt, Germany.
Plant, Soil and Agricultural Systems, Southern Illinois University, MC 4415, Carbondale, IL 62901, USA.
Sensors (Basel). 2018 Jun 29;18(7):2087. doi: 10.3390/s18072087.
Gasoline engine oil (SAE 5W-20) was subjected to thermal oxidization (TO) for four periods of time (0 h, 48 h, 96 h and 144 h) and exposed to THz-time domain spectroscopy (TDS) measurement. Error contributions from various error sources, such as repeatability errors, assembly errors of the probe volume and errors caused by the TDS system were evaluated with respect to discernibility and significance of measurement results. The most significant error source was due to modifications of the TDS setup, causing errors in the range of 0.13% of the refractive index for samples with a refractive index around 1.467 and a probe volume length between 5 and 15 mm at 1 THz. The absorption coefficient error was in the range of 8.49% for an absorption around 0.6 cm. While the average of measurements taken with different setup configurations did not yield significant differences for different TO times, a single, fixed setup would be able to discern all investigated oil species across the entire frequency range of 0.5⁻2.5 THz. The absorption coefficient measurement showed greater discernibility than the measurement of the refractive index.
汽油发动机油（SAE 5W-20）经历了四个时间段的热氧化（TO）（0 h、48 h、96 h 和 144 h），并进行太赫兹时域光谱（TDS）测量。从重复性误差、探针体积的组装误差以及 TDS 系统引起的误差等各种误差源的角度，评估了它们对测量结果的可辨别性和显著性的影响。最显著的误差源是由于 TDS 设备的修改，导致折射率约为 1.467 的样品的折射率和探针体积长度在 1 THz 时的误差在 0.13%范围内，对于吸收率约为 0.6 cm 的情况，吸收系数误差在 8.49%范围内。虽然不同设置配置的测量平均值对于不同的 TO 时间没有产生显著差异，但单个固定设置将能够在 0.5⁻2.5 THz 的整个频率范围内辨别所有研究的油样。吸收系数测量比折射率测量具有更高的可辨别性。
