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Pressure and Measurement Terminology from A-Z Absolute Pressure A pressure measured relative to a perfect vacuum. Atmospheric Pressure The total outside air pressure measured with reference to absolute vacuum. The pressure varies depending on geographical location, altitude and local weather conditions. Barometric Pressure The total outside air pressure measured with reference to absolute vacuum. The pressure varies depending on geographical location, altitude and local weather conditions. Calibration The comparison of a pressure sensor output against the output of a reference standard. Creep The change in a sensors output occurring with time after removal of a load which had been applied for a specific period. Creep Recovery The change in no-load output occurring with time after removal of a load which had been applied for a specific period. Drift A random change in output under constant load or pressure conditions. Full Scale The maximum measurement range for which a pressure sensor is calibrated. Hysteresis The maximum difference between pressure sensor output readings for the same applied load; one reading obtained by increasing the measurement from zero and the other by decreasing the measurement from rated capacity. Long Term Stability or Long Term Drift The amount of change of a measured reading at exactly the same pressure and ambient conditions over a given period of time which is typically quoted as an annual figure. Measurement A physical measured, quantity/property or condition which is measured. Maximum Pressure Hysteresis The largest difference between measurements recorded during an increase in pressure from zero to full scale pressure and a decrease in pressure from full scale to zero pressure. Measurement Precision The limit that any pressure measurement reading will deviate from the best straight line. Non-Linearity The limit that any pressure measurement readings recorded from a series of increasing pressures will deviate from the best straight line. Overpressure The maximum pressure that can be applied to a pressure instrument without significantly effecting its reading accuracy. Some manufacturers will state a maximum calibration shift following an over-pressure condition where others will state that the specification is unaffected. Pressure The amount of force or load applied to a unit area; Force divided by Area = Pressure; the SI unit for pressure is the Pascal (Pa) which is derived from Kilogram per Meter Squared (kg/m2). Repeatability The amount of change of a measured reading at exactly the same pressure and ambient conditions over a series of pressure cycles from zero to full scale pressure and back to zero again. To ensure no Pressure Hysteresis is introduced into Repeatability measurement, readings are always taken during an increase in pressure or a decrease in pressure but never a mixture of the two. Span The amount of change in measured output or reading from zero to full scale pressure. Span Offset The deviation in Span output or reading from the ideal point at full scale pressure. Span Sensitivity The ratio of a change in measured output or reading to a change in pressure. Sensor Element An individual sensing element within a Sensor Array. Standard Atmosphere or ATM A universally adopted standardized pressure reading for barometric pressure at sea level and equals precisely 1013.25mb absolute. Standard atmosphere is a particularly useful datum point in altitude measurement since all altimeters are calibrated to this pressure. Tactile Sensing The detection and measurement of the spatial distribution of forces perpendicular to a sensing array, and the subsequent interpretation of the spatial information. A tactile-sensing array is a coordinated group of Sensor Elements. Thermal or Temperature Errors The limit of change of any pressure output or reading over a given operating temperature range. Thermal Span Sensitivity The amount the Span output or reading at full scale pressure has changed between two different temperatures. This error is also often expressed as a percentage of full scale per degree Celsius or Fahrenheit e.g. ±0.01%FS/DegF. Thermal Zero Error The amount the output or reading at Zero Pressure has deviated between two different temperatures. This error is often expressed as a percentage of full scale per degree Celsius or Fahrenheit e.g. ±0.02%FS/DegC. Zero Offset The deviation in output or reading from the ideal point at zero pressure. Zero Tare The operation of removing any Zero Offset to obtain the optimum measurement at zero pressure. 
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