I know that the average PSI at sea level is 14.7 PSI, I just don’t understand why gauges and other PSI measuring equipment dont account for outside atmospheric conditions.
For example, if you were filling a scuba tank at sea level, the gauge would say 0 PSI instead of 14.7. And when you do fill the tank up by 100 PSI (I don’t know how much a scuba tank holds), it would say 100, not 114.7.
It’s the same with vacuum chamber gauges. Instead of going from 14.7-0, they go from 0 to around -30 PSI. Where is the extra 15.3 PSI coming from? I assume that it is just standard to start at 0 PSI for all gauges, but it’s a bit confusing. Because if you were were on top of a mountain then the gauge wouldn’t be accurate.
In: Physics
Your question has been answered elsewhere, but I wanted to point something out:
> It’s the same with vacuum chamber gauges. Instead of going from 14.7-0, they go from 0 to around -30 PSI.
I highly doubt this.
They probably go from 0 to around -30 inches of mercury (often labeled ‘inHg’ or ‘”Hg’). 1 inch of mercury is about 0.49 PSI, so -30″ is about -15 PSI, which matches up very nicely to the fact you would expect a good vacuum to be.
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