Measurements made by deep floats had a salinity bias with a negative pressure dependency. Salinity is affected by conductivity measurements via changes in the CTD measuring cell geometry under pressure. To remove the effect, a canceling factor for pressure CP_cor is prepared theoretically by the manufacturer considering the isotropic deformation of a single-cylinder measuring cell under pressure; the observed negative pressure dependency, however, requires an even smaller CP_cor. This study examined the causes of the inconsistency for salinity measurements with a dual-cylinder cell model, considering that the actual CTD measuring cell is a glass cell covered by a polyurethane jacket. The dual-cylinder cell model clarifies that the CTD measuring cell deforms anisotropically to yield a smaller CP_cor; mainly because the inner glass cell deforms radially to a greater extent than the single-cylinder model due to the radial stress from the outer cylinder (jacket) being stronger than the hydrographic pressure. The observed fresh bias at the sea surface is attributed to a slight shrinkage of the outer jacket because of compression set of polyurethane in deep ocean. The shrunken polyurethane jacket is elongated over time due to a creep phenomenon, which causes less-freshening of the fresh bias found at the sea surface. The observed linear relationship between the smaller CP_cor and the fresher bias at the sea surface is attributed to the variation of the wall thickness of the polyurethane jacket when it shrinks similarly. The study suggests another idea to improve the salinity accuracy of CTD sensors greatly: a change of the jacket material into an elastomer. The improvement makes the present setting of CP_cor be more valid and reliable, because the elastomer jacket hardly affects the change of the measuring cell geometry under pressure, which in turn removes the pressure effects on salinity measurements.

深浮标测量结果的盐度偏差与负压相关。盐度受电导率测量的影响，这是通过在压力下改变CTD测量池的几何形状来实现的。为了消除这种影响，制造商从理论上考虑了单缸测量单元在压力下的各向同性变形，准备了压力CP _cor的抵消因子。但是，观察到的负压依赖性需要更小的CP _cor。这项研究考虑了实际的CTD测量池是由聚氨酯外套覆盖的玻璃池，因此研究了双缸池模型盐度测量不一致的原因。双圆柱单元模型阐明了CTD测量单元会各向异性变形以产生较小的CP _cor; 主要是因为内部玻璃单元的径向变形比单圆柱模型大，这是由于来自外部圆柱（夹套）的径向应力大于水文压力。由于深海中聚氨酯的压缩永久变形，在海面观察到的新鲜偏斜归因于外套的略微收缩。由于蠕变现象，收缩的聚氨酯护套会随着时间的流逝而伸长，这会导致在海面发现的新鲜偏斜的鲜化程度降低。较小CP _cor之间观察到的线性关系而在海面较新的偏斜则是由于聚氨酯外套在类似收缩时壁厚的变化而引起的。这项研究提出了另一种可以大大提高CTD传感器盐度精度的想法：将护套材料变成弹性体。这种改进使当前的CP _cor设置更加有效和可靠，因为弹性体外套几乎不影响压力下测量单元的几何形状变化，从而消除了对盐度测量的压力影响。