Covariance Matrix Evaluation in Correlated Type B Measurement Uncertainty Propagation
Evaluating input covariance matrices in Type B propagation prevents underestimating multi-channel variance and ensures valid system uncertainty limits.
Paired Transducers
Hardware Matching
Sensor configurations using two identical measurement units selected for their matching performance characteristics improve the accuracy of differential measurements. Deploying paired transducers allows systems to cancel out common environmental interferences such as ambient temperature changes and line pressure variations. These sensors are selected from the same production batch to ensure identical materials and construction.
Measurement Execution
The two sensors are installed at opposing points in the system to capture differential data directly. In ultrasonic flowmeters, one sensor transmits a signal while the other receives it, and then the roles are reversed to measure the transit time in both directions. This alternating measurement cancels out the effect of fluid properties and isolates the flow velocity.
Thermal Balance
Placing both sensor units in close physical proximity ensures they experience the same environmental changes. If one sensor is exposed to a different temperature than the other, the differential output will drift and introduce errors. High-conductivity metal clamps are used to maintain thermal equilibrium between the two units.
Calibration Certificate
Documented testing results verify that the two sensors maintain their matched response across the entire operating range. The certificate lists the differential error between the two units under reference conditions. This documented performance is required for custody transfer systems.