Establishing Measurement Traceability Chains for Industrial Pressure Transducers
Establishing pressure traceability requires calculating complete uncertainty budgets and enforcing accredited test ratios to prove sensor claims.
End Point Calibration
Alignment Methodology
A calibration procedure that aligns the output of an instrument at the lower and upper limits of its measuring range establishes a simplified response curve. This method, known as end point calibration, forces the instrument output to agree perfectly with reference standards at zero and full scale. Adjusting these two points simplifies the calibration process and ensures maximum accuracy at the extremes of the operational span.
Linearity Adjustment
Deviations from a perfectly straight line between the two adjusted extremes are not corrected by this approach. During end point calibration, the technician assumes a linear relationship between the endpoints, which can lead to larger measurement uncertainties in the middle of the range. If the sensor has a non-linear response, other multi-point calibration methods must be used instead to ensure accuracy across the entire span.
Operational Constraint
Selecting this technique is typical when the primary measurement task occurs predominantly at either the zero point or the maximum limit. Utilizing end point calibration reduces the time and expense required for testing because only two points need verification. Many industrial pressure switches and relief valves are qualified this way because their critical actions occur at these specific thresholds.
Instrument Setting
Standard procedures involve setting the zero adjust and then applying the full scale input to set the span adjust. Applying end point calibration requires repeating these steps until both limits stabilize.