Low Pressure Manometry Standards & Calibrations

 NIST has developed best-in-the-world primary standard pressure measurement capabilities for pressures spanning the range of 0.01 Pa to 360 kPa through the operation of four liquid-column manometers. While the principle behind the primary standard is simple, the manometers are operationally complex, requiring accurate determination of temperature, density, gravity, speed of sound, and ultimately column height. The NIST-designed manometers are unique in that they use an ultrasonic interferometric technique that enables operational column height resolution of 10 nm to 20 nm. Custom electronics and software implement a pulse-echo technique that uses the change in phase between sent and received radio-frequency acoustic signals to determine the length of a mercury or oil column. A diffraction correction model further refines the technique.

3-meter Mercury Manometer
The 360 kPa Ultrasonic Interferometer Manometer provides the nation with best-in-the-world capabilities for measuring absolute and differential pressure from 1 Pa to 360 kPa with an expanded uncertainty (k=2) of [(6 x 10^-3 Pa)² + (5.2 x 10^-6 * P)²]^1/2, where P is the pressure being measured. It is primarily operated for calibration of piston gauges (absolute or differential) between the pressures of 10 kPa and 360 kPa.

1-meter Mercury Manometer
The 160 kPa Ultrasonic Interferometer Manometer provides the nation with best-in-the-world capabilities for measuring absolute and differential pressure from 1 Pa to 160 kPa with an expanded uncertainty (k=2) of [(6 x 10^-3Pa)²+ (5.2 x 10^-6 * P)²]^1/2, where P is the pressure being measured. It is primarily operated for calibration of capacitance diaphragm gauges, resonance silicon gauges, or quartz Bourdon gauges between the pressures of 1 Pa and 360 kPa.