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Understanding Vacuum Measurement: Key Terms

Posted by Tom Bassi on Jun 10, 2014 8:00:00 AM

In the vacuum industry, and when working with digital vacuum gauges, key terms that one must understand are measurement and pressure.  Better grab an Espresso for this one....

In the following infographic, ambient pressure 

is the pressure of the air pushing out on a closed tank. This could be a balloon or a vacuum vessel. Air pressure is the pressure of the weight pushing down on a given object at any point. We use vacuum
Balloon_AmbientPressure to measure when the pressure is less than ambient pressure. UNITS OF MEASUREMENT ABSOLUTE MEASUREMENT: Real and true measurement by standard unit. For example:
    • age in years
    • cost in dollars
    • vacuum in torr
  • DIFFERENTIAL MEASUREMENT: The difference between 2 measures. For example:If you have 3 cars and I have 1 car, then there is a differential of 2 cars. 
    • If you have a chip bag and are standing on top of Pike's Peak, the pressure on that bag may be 650 Torr. If you have the same chip bag at the beach, the pressure is about 760 Torr. The chip bag will look deflated on Pike's Peak and properly inflated at the beach. Your vacuum measure matters to you if you care about smooshed chips.
  • GAUGE MEASUREMENT: The difference in pressure between atmospheric pressure and what you are measuring. This is what we are measuring with our vacuum gauge.
    • If your item has 700 torr, and standard atmospheric pressure is 760 torr then th
    • e gauge measure is 60 torr.
    • An interesting note: gauge pressure = differential pressure where one side of the differential pressure is atmospheric pressure.  Fun!

Understanding NIST standards is the next step in learning about vacuum measurement. See our blog post on this topic. You can also check out our reference document on vacuum measurement, or view calibration standards for specific prodoucts.

  Ask A Question  your questions about vacuum! We look forward to providing you an educational response that helps you do your job better!

Topics: HVAC, Accuracy