A Faster Way to Calibrate Piston Gauges

For industry and government labs to ensure their pressure-measurement machines are working correctly, they need a reliable source of pressure. Often, that source is a piston gauge – a cylinder of metal that falls through a hollow cylinder or “sleeve” at a predictable rate. Staff at NIST’s Physical Measurement Laboratory (PML) perform precise calibrations of piston gauges for customers including the Navy, the Army, airlines, and power utility companies. For decades, those calibrations were done painstakingly by hand. But staff have recently developed and launched a new, automated system that dramatically reduces the time required for each test. Pressure is a measurement of the amount of force applied to a unit area. For a piston gauge, that force comes from a mass that is placed on top of the piston, pushing it down. The area in this case is the cross-sectional area of the piston, corrected for distortion and defects and referred to as the “effective area.”  So for piston gauges, pressure is dependent on the effective area of the piston and how much mass is placed on it. To measure pressure precisely, companies need a reliable pressure source. Often, that source is a piston gauge.

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