A colleague approached me and asked what I used as a rule of thumb for the percent of error in gas measurement per degree off calibration. I used the same .1% per degree he did. Upon

checking this out later, I found the Ft error was .192% per degree. On further research the total error was .234% per degree. The reason for the change?

The additional effect of supercompressablility, F pv.. Of course the effect of F t was constant while the F pv varied with the absolute pressure. The colleague brought it to my attention

because the pipe line correction appeared to be double what he expected. Had the error been in the opposite direction, the total error would have been only .15%, since the effects

of temperature on F t and F pv are inverse to each other when the error is negative. The general rule we used for temperature was off by a factor of 2 and was variable, depending on the absolute pressure.

ROLLINS,R. (2014) Rules of thumb in Gas Measurement