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Vacuum & Units

  1. Nov 9, 2006 #1
    Im just wondering, is a higher or lower reading of a number in inHG units indicating a stronger or weaker vacuum?

    For Example:
    What is creating a stronger vacuum?
    15inHG or 10inHG

  2. jcsd
  3. Nov 9, 2006 #2

    Doc Al

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    Staff: Mentor

    Often vacuums are measured in inHG (aka: inches of mercury) below atomospheric pressure (as a gauge pressure). Thus 15 inHG would be a stronger vacuum than 10 inHG.

    But inHG can also used as a direct measure of pressure (conventional or absolute pressure), in which case: the lower the pressure, the stronger the vacuum.
  4. Nov 14, 2006 #3
    We often use the unit mTorr to indicate vacumm. 1 Torr equals 1mmHg. So the vacuum reaches 76mTorr means the pressure is 10e-4 times smaller than the ambient pressure. Higher vacuum (lower pressure) can be measured in 10^-5 - 10^-7 Torr.
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