Calibration Techniques & Procedures Flashcards

A calibration technician notices that repeated measurements of the same input produce results that cluster tightly but are consistently offset from the true value. This describes:

Answer: Good precision with poor accuracy (systematic bias)

Tight clustering indicates good precision (repeatability), but a consistent offset from true value is a systematic error (bias), meaning accuracy is poor despite high repeatability.

ISO/IEC 17025 requires that calibration laboratories maintain traceability to national measurement standards. The primary purpose of this requirement is to:

Answer: Ensure measurement results are comparable and compatible worldwide

Traceability provides an unbroken chain of comparisons to national or international standards, ensuring measurements are universally meaningful and comparable.

The guard band technique in calibration decision-making is used to:

Answer: Account for measurement uncertainty when making pass/fail decisions near tolerance limits

Guard banding narrows the acceptance zone by the measurement uncertainty, reducing the probability of falsely accepting an out-of-tolerance instrument.

When calibrating a digital multimeter's AC voltage function, the reference standard's frequency accuracy matters because:

Answer: Many DMMs have frequency-dependent AC response that affects amplitude accuracy

AC voltage accuracy in DMMs is specified over a frequency range, and errors can increase outside that range due to bandwidth limitations and RMS conversion circuitry characteristics.

A calibration procedure calls for a 30-minute warm-up period before taking readings. Skipping this step most directly risks errors caused by:

Answer: Thermal drift as internal components stabilize to operating temperature

Electronic components change their characteristics as they warm up; specifications are valid only after thermal equilibrium is reached, so skipping warm-up introduces thermally-induced drift errors.

When calibrating a load cell, the technician applies dead-weight loads and records outputs. A 'creep' test involves:

Answer: Holding a constant load and observing any change in output over time

Creep is the slow change in output signal under a constant applied load over time, and a creep test documents this characteristic by monitoring output drift at a fixed input.

In liquid-in-glass thermometer calibration, the 'emergent stem correction' is needed when:

Answer: Part of the liquid column extends above the calibration bath and is at a different temperature than the bath

When part of the thermometer stem is outside the calibration medium, that portion of liquid is at ambient temperature rather than bath temperature, introducing a predictable but significant error requiring correction.