Measurement and Instrumentation

A: Re-zeroing masks a real installation-induced pressure imbalance and will cause a latent offset once flow resumes, driving nuisance trips later. Stretching the alarm delay allows the logic to accept an invalid process state and risks missing a genuine loss of flow. Swapping impulse lines inverts the sign but leaves the root cause untouched and breaks calibration traceability. Sequencing the valves removes the trapped low-side condition that drives negative DP and the interlock enforces it every time.

A: Basing the decision on spurious trip history confuses availability with risk reduction and ignores hidden failures. Datasheet MTBF doesn't translate directly to PFDavg without proof test effectiveness and failure modes. Voting reduces some random failures but doesn't waive the need to show compliance when proof testing is stretched. IEC 61511 expects a quantitative PFDavg check with all assumptions explicit before any interval change.

A: Halving the denominator double-counts compensation that isn't present and understates the error. Treating ohms as percent ignores the RTD slope definition and inflates the result. Assuming full cancellation misses the imbalance explicitly stated and drives false confidence. Using the linear RTD relation gives 1 Ω divided by 0.00385×100 Ω, landing near 2.6°C.

A: Cranking pump speed alters system hydraulics and masks the measurement error while increasing parasitic losses. Offsets tied to temperature without physics drift as viscosity changes with aging. Mode switching doesn't address signal transit-time sensitivity to velocity profile. Low-Re effects are known for ultrasonic meters and the fix lives in calibration or selection.