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在石油密度测定中,经常要把视密度换算成20℃的标准密度。一般是通过密度计测得视密度和试油温度,再根据“石油密度换算表”查表求得。但表中温度的最小分度值为1℃或0.5℃,视密度的最小分度值为0.001克/厘米~3或0.005克/厘米~3。只有当测定时试油温度的数值小数后第一位为0或5,视密度的数值小数第三位为0～9,第四位为0时,才能在表中直接查出20℃的密度。当视密度和温度不符合上述条件时,要按比例进行内插求值,比较麻烦,需要较长的时间才能换算出结果,而且也容易出错。
In the determination of petroleum density, visual density is often converted to a standard density of 20 ℃. Density is generally measured by the apparent density and test oil temperature, and then according to “oil density conversion table” look-up table obtained. However, the minimum temperature in the table is 1 ° C or 0.5 ° C, and the minimum apparent density is 0.001 g / cm 3 or 0.005 g / cm 3. Only when the test oil temperature after the decimal fraction of the first number is 0 or 5, depending on the value of the decimal third decimal place 0 to 9, the fourth is 0, the table can be directly detected in the density of 20 ℃ . When the apparent density and temperature do not meet the above conditions, it is more troublesome to calculate the interpolation according to the proportion, takes a long time to calculate the result, and is also prone to error.