Vacuum pressure on the 170
Expressing "vacuum" using the term "pressure" is completely legitimate. No different than the many ways of expressing the two in terms of different measurement standards, whether "pounds per square inch," or inches of orange juice.
In fact, in a different life, I used one of these................
Which is a Bacharach brand oil filled manometer. The thing is, while it is marked and calibrated in "inches of water" that is NOT what is IN it. So it actually does not MEASURE "inches of water," because the OIL that is used is not actually responding to the same height. In other words, if you would substitute an "inch ruler" for the calibrated scale, the instrument would read incorrectly
The point?
You COULD build yourself an instrument that reads in "millimeters of sludge." Or in "feet of 3-in-1 oil" It just so happens that water and mercury are two standards that we "use a lot."
Expressing "vacuum" using the term "pressure" is completely legitimate. No different than the many ways of expressing the two in terms of different measurement standards, whether "pounds per square inch," or inches of orange juice.
In fact, in a different life, I used one of these................
Which is a Bacharach brand oil filled manometer. The thing is, while it is marked and calibrated in "inches of water" that is NOT what is IN it. So it actually does not MEASURE "inches of water," because the OIL that is used is not actually responding to the same height. In other words, if you would substitute an "inch ruler" for the calibrated scale, the instrument would read incorrectly
The point?
You COULD build yourself an instrument that reads in "millimeters of sludge." Or in "feet of 3-in-1 oil" It just so happens that water and mercury are two standards that we "use a lot."
