List of Terms Used in Pressure Calibration
1. Types of Pressure
Calibration Measurements
Absolute Pressure (a):
Measured relative to a perfect vacuum (zero pressure).
Gauge Pressure (g):
Measured relative to the current local atmospheric pressure.
Differential Pressure
(d/diff): The difference between two pressure points.
Compound Pressure:
Measurement range covering both vacuum and positive pressure.
Vacuum Pressure (v):
Pressure below atmospheric pressure, often in inHg or torr.
Sealed Gauge: Pressure
measured relative to a sealed reference atmosphere, not local ambient.
2. Core Metrological
Terms
Accuracy: Closeness of
a measured value to the true value, including linearity, hysteresis, and
repeatability.
Calibration: Comparing
device readings against a higher-accuracy known standard.
Adjustment: Modifying
an instrument to meet performance standards.
Precision: Ability to
produce consistent results under identical conditions.
Uncertainty:
Quantified doubt about measurement reliability.
Traceability: Unbroken
chain linking measurements to national/international standards.
Repeatability:
Agreement between consecutive measurements under the same conditions.
Reproducibility:
Consistency of measurements under changed conditions (operator, time,
location).
3. Key Performance
Parameters
Hysteresis: Max
difference in output at the same pressure between increasing and decreasing
pressure.
Linearity: Max
deviation from a specified straight line (e.g., Best Fit Straight Line).
Resolution: Smallest
detectable change in pressure shown by the instrument.
Span: Difference
between the upper and lower range limits (e.g., 0-100 psi span is 100).
Zero Shift (Offset):
Output change at zero pressure, often due to thermal or physical effects.
Drift: Gradual change
in measurement characteristics over time.
Total Error Band
(TEB): Maximum deviation considering temperature, pressure, and environmental
factors, a comprehensive accuracy measure.
4. Technical Terms
& Abbreviations
DUT/UUT: Device/Unit
Under Test.
P/I & I/P:
Pressure-to-Current / Current-to-Pressure conversion (e.g., 3-15 psi to 4-20
mA).
TUR/TAR: Test
Uncertainty Ratio / Test Accuracy Ratio (standard vs. DUT accuracy).
Deadweight Tester:
Primary, highly accurate pressure source using calibrated weights and piston.
Head Height
Correction: Adjustment for vertical height difference between standard and DUT.
Air Buoyancy
Correction: Correction for air effect on weights in deadweight testers.
Bourdon Tube:
Mechanical sensing element that bends under pressure.
Transducer vs.
Transmitter: Transducer outputs unamplified mV signal; transmitter outputs
amplified, standardized signal (4-20 mA, 0-10 V).
As Found / As Left:
Data recorded before and after adjustment.