Calibration Techniques & Procedures Flashcards

A calibration standard with a stated uncertainty of ±0.01% and a 95% confidence level means:

Answer: There is a 95% probability that the true value falls within ±0.01% of the standard's reported value

Uncertainty at a stated confidence level means the true value lies within the stated interval with that probability, not that it is guaranteed to be within that interval.

Which method is most appropriate for calibrating a high-accuracy platinum resistance thermometer (PRT) in the range of 0°C to 660°C?

Answer: Fixed-point calibration at ITS-90 defined phase transition temperatures

ITS-90 fixed points (such as the freezing points of tin, zinc, and aluminum) provide the most accurate reference temperatures and are the accepted method for primary PRT calibration.

When documenting a calibration, the minimum traceability statement on the certificate must include:

Answer: The reference standards used, their calibration certificates, and the accrediting body

Traceability documentation must identify the standards used and link them to an unbroken chain back to national or international standards through their certificates and the body that accredited them.

A calibration technician is using a fluke 5522A multi-product calibrator to calibrate an oscilloscope. To verify the oscilloscope's vertical gain accuracy, the technician should output:

Answer: A sine wave at a known frequency and amplitude

Vertical gain accuracy is verified by comparing the oscilloscope's displayed amplitude of a sine wave to the calibrator's precisely known output amplitude at a specific frequency.

The 4:1 test accuracy ratio (TAR) rule specifies that the calibration standard's accuracy should be at least 4 times better than the tolerance of the instrument being calibrated. This ratio exists primarily to:

Answer: Limit the probability that standard uncertainty contributes significantly to conformance decision errors

A 4:1 TAR ensures the standard's error is small relative to the UUT tolerance, reducing the risk of incorrectly accepting or rejecting the UUT due to standard uncertainty.

Environmental conditions recorded during calibration (temperature, humidity, pressure) are required primarily because:

Answer: Many instruments' characteristics vary with environment, affecting measurement results and uncertainty

Temperature, humidity, and pressure affect both the standard and the UUT; recording conditions allows corrections to be applied and uncertainty contributions from environment to be quantified.

When calibrating a precision resistor using the substitution method, the reference and unknown resistors are measured sequentially with the same bridge/meter to:

Answer: Cancel out systematic errors of the measuring instrument itself

In substitution, the measuring instrument reads both resistors under identical conditions, so any instrument bias cancels when the ratio of readings is taken, yielding a more accurate comparison.