PRESSURE CALIBRATION
PTC METROLOGY™ CALIBRATION LAB
Primary Standards
- Ruska 2400 HL Deadweight Tester from 0.2 to 12140 psig with an uncertainty of ±50 parts in 106
- Ruska 2465 Pneumatic Deadweight Tester 0.2 to 1000 psia ±10 parts in 106
- Ruska 2470 Pneumatic Deadweight Tester 0.2 to 3000 psig ±25 parts in 106
Secondary Standards
- Vacuum/ Low Pressure GP 275 Thermocouple Gage 0.01 to 1 Torr ±5% I.V.
- Barometric Pressure Wallace and Teirnan 600 ±5mm Hg
Relative or Gauge Pressure
Pressure is usually measured, either as absolute pressure (psia), or relative to atmospheric pressure (psig). Such measurements are called gauge pressure. An example of this is the air pressure in a car tire, which might be said to be "35 psi," but is actually 35 psi above atmospheric pressure. Since atmospheric pressure at sea level is about 14.7 psia, the absolute pressure in the tire is therefore about 49.7 psi.
Atmospheric Pressure
Atmospheric pressure is the pressure exerted by the air around us. The pressure varies both with altitude, and weather patterns. Standard atmospheric pressure at sea level is defined as 1 atmosphere equal to 760 millimeters of mercury (760 Torr) and 101,325 Pascals. 29 117/127 inches of mercury 29.92 inHg 14.6959 psia or 0 psig (pounds-force per square inch, absolute or gauge lbf/in 2
Absolute Pressure
The total pressure exerted on a system, equal to the gauge pressure plus atmospheric pressure. (psia)
Gauge Pressure
The pressure of a system measured by a gauge, which excludes atmospheric pressure. (psig)