Measurement Uncertainty & Calibration Flashcards
6 cards from real FCC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Measurement Uncertainty & Calibration flashcards as text
What is a 'reference standard' in laboratory calibration and what role does it play in an FCC lab?
Answer: A measurement standard with the highest metrological quality in a lab, used to calibrate working standards
A reference standard is the highest-accuracy measurement standard maintained in a laboratory, used to calibrate working/transfer standards and test equipment, establishing the traceability chain to national standards.
How does temperature affect measurement uncertainty in an FCC laboratory?
Answer: Temperature changes can affect cable attenuation, amplifier gain, and receiver response, all of which must be characterized and included in the uncertainty budget
Variations in ambient temperature can change the electrical characteristics of cables, amplifiers, and receivers, introducing systematic errors in measurements that must be quantified and included in the laboratory's uncertainty analysis.
What is the purpose of a 'check standard' or 'control chart' in an FCC testing laboratory?
Answer: To monitor the ongoing performance of measurement equipment between calibrations by tracking measurements of a stable reference artifact
A check standard is a stable artifact measured periodically, and control charts plot the results over time to detect drift or degradation in equipment performance before it affects compliance test results.
What is 'combined standard uncertainty' (uc) and how is it calculated?
Answer: The positive square root of the sum of variances of all uncertainty components, whether Type A or Type B
Combined standard uncertainty is calculated by taking the positive square root of the combined variance, which is the sum of squared standard uncertainty contributions from each independent source (root-sum-of-squares method).
Why must measurement uncertainty be considered when a test result is within 6 dB of the FCC emission limit?
Answer: Results within the uncertainty range of the limit cannot be definitively declared passing without accounting for whether the true value could exceed the limit
When a measured value is close to the emission limit, the measurement uncertainty determines whether the true emission level could actually exceed the limit, making it essential to assess the risk of a false compliance declaration.
What does it mean for a calibration to be traceable to NIST?
Answer: Each step in the calibration chain has documented uncertainty linking it back to primary standards maintained by the National Institute of Standards and Technology
NIST traceability means there is an unbroken chain of calibrations, each with stated uncertainties, from the laboratory's working standards back to the primary measurement standards maintained by NIST, ensuring nationally consistent measurements.