Calculating vacuum -- These numbers do not make sense

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SUMMARY

The forum discussion centers on the challenges of accurately reading a manometer in a vacuum pump setup. The user reports achieving a reading of 80 inches of water (H2O), which is deemed impossible given the physics of vacuum pressure. Experts clarify that a reading of 40 inches H2O corresponds to approximately 0.9 atm, while 80 inches would exceed physical limits. The conversation emphasizes the importance of understanding the differences between water and mercury manometers and the necessity of proper setup to obtain reliable measurements.

PREREQUISITES
  • Understanding of vacuum pressure and its measurement
  • Familiarity with manometer types, specifically water and mercury manometers
  • Knowledge of atmospheric pressure and its effects on fluid dynamics
  • Basic principles of fluid mechanics, including Boyle's Law
NEXT STEPS
  • Research the principles of manometer operation and design
  • Learn about the differences between water and mercury manometers
  • Study the effects of atmospheric pressure on fluid measurements
  • Explore vacuum pump technologies and their applications in laboratory settings
USEFUL FOR

This discussion is beneficial for engineers, laboratory technicians, and anyone involved in vacuum technology or fluid dynamics, particularly those working with manometers and vacuum pumps.

  • #31
Fixed I think. Bought a gauge that went as low as -100 kpa and it went well past that and hard up against the stopper at around where the -130 kpa graduation would have been if had been marked. Must have gone well past that level though as when I repeated the test the gauge only got as low as roughly -110 so I’m thinking the gauge was damaged in the initial test or it found a way to admit a small amount of air into the tank , perhaps through the pump seals. Either way it has proven to be more than is required. Thanks for all your input.
 
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