I have been studying for a major test, and one of the questions involve converting mercury readings. I've looked all over the place, but have not found any answers - not in my books, and not using Google.
The question involves converting Inches of Mercury Absolute and Inches of Mercury Vacuum (Gage) .
I found threw doing some math that it is easy to convert between " HgV and " HgV.
No matter what you have, to convert to the other pressure, subtract 29.921 from your given pressure. If the answer is negative, convert it to positive.
Example 1. You have 12 " HgV and want to know how much HgA you have.
12 - 29.921 = -17.921 Your answer is 17.921 " HgA
Example 2. You have 25 " HgA and want to know how much HgV you have.
25 - 29.921 = -4.921 Your answer is 4.921 " HgV