How do you convert the reading of a gage from Hg to PSI for calculations?

How do you convert the reading of a gage from Hg to PSI for calculations?

• A. By subtracting 14.7 from the Hg reading
• B. By adding 14.7 to the Hg reading
• C. By using the conversion factor
• D. By multiplying the Hg reading by 0.0361

Answer: (B)

To convert the reading of a gauge from inches of mercury (Hg) to pounds per square inch (PSI), it is essential to account for atmospheric pressure, which is typically around 14.7 PSI at sea level. Since gauge pressure measures the pressure relative to atmospheric pressure, adding 14.7 to the Hg reading accurately translates the measurement into absolute pressure in PSI. In practice, the formula used for conversion from Hg to PSI is: \[ \text{PSI} = (\text{Hg reading} \times 0.49118) + 14.7 \] This illustrates that after converting the Hg reading itself into PSI (using the appropriate factor for conversion), the ambient atmospheric pressure (14.7 PSI) is then added to this value to provide an absolute pressure reading. Other methods of conversion, such as directly multiplying or using specific conversion factors, won't yield the correct absolute pressure representation because they don't take into account the standard atmospheric pressure that is consistently present in these calculations. This demonstrates the significance of adding 14.7 to encompass both gauge and atmospheric pressure for accurate results.

To convert the reading of a gauge from inches of mercury (Hg) to pounds per square inch (PSI), it is essential to account for atmospheric pressure, which is typically around 14.7 PSI at sea level. Since gauge pressure measures the pressure relative to atmospheric pressure, adding 14.7 to the Hg reading accurately translates the measurement into absolute pressure in PSI.

In practice, the formula used for conversion from Hg to PSI is:

[ \text{PSI} = (\text{Hg reading} \times 0.49118) + 14.7 ]

This illustrates that after converting the Hg reading itself into PSI (using the appropriate factor for conversion), the ambient atmospheric pressure (14.7 PSI) is then added to this value to provide an absolute pressure reading.

Other methods of conversion, such as directly multiplying or using specific conversion factors, won't yield the correct absolute pressure representation because they don't take into account the standard atmospheric pressure that is consistently present in these calculations. This demonstrates the significance of adding 14.7 to encompass both gauge and atmospheric pressure for accurate results.