压力和温度对静力水准系统精度影响分析

静力水准系统(Hydrostatic leveling system,HLS)的工作介质是液体.由于纯净水的诸多优点,在本系统中采用水作为工作介质.液体的特性是极易受到外界的影响而改变它的物理形态.在HLS系统中,压力、温度等因素对系统的测量有着非常大的影响.本文分别分析了压力和温度对静力水准系统测量精度的影响.为了消除压力的影响,在系统设计的时候采用了密封钵体和钵体之间用等压气管连接的办法,保证系统在工作时每个钵体中的工作液体表面上的大气压是一致的.温度的影响包括水管中温度梯度的影响和钵体之间温度差异的影响.通过分析,对于水管中温度梯度的影响,只要在安装系统时保证水管的垂直高差足够小,就可以忽略;而对于钵体之间的温度差异的影响,在每个钵体传感器中都安装了温度传感器,实时地测量钵体的温度,并和CCD测量数据同时采集,通过理论计算得到温度修正公式,对每个钵体中的CCD读数进行温度修正.通过实验数据分析,可以把温度的影响修正到允许的误差范围以内.

Analysis of influence of pressure and temperature on HLS

In the hydrostatic leveling system (HLS) the working medium is liquid. Because of its merits, water is chosen as the working medium in the HLS. In the HLS system both pressure and temperature have great effects on the surveying results. In this article the influences of pressure and temperature on the HLS are analysed. In order to dispel the influence of pressure on the system, sealing the vessels and connecting the whole system to a common air circuit were adopted as the solution. This circuit was set under ambient atmospheric pressure at a single point of the network. The influence of temperature on HLS includes the temperature gradients existing in the water pipes and thetemperature difference among vessels. After analysis we know that, if we can keep the water level of the pipes as equal as possible when the system is assembled, the influence of the temperature gradient can be eliminated effec- tively. For correcting the effect of temperature variation among vessels, temperature sensors were installed in every vessel to survey the real-time temperatures, and the data were be collected along with the CCD data. And it is through theoretical analysis that we can get the correction formula, by which the errors resulting from the temperature varia- tion can be corrected.