Measurement Standards & Accuracy Flashcards

What does the term 'traceability' mean in the context of weighing standards?

Answer: An unbroken chain of comparisons linking measurements to national or international standards

Traceability means an unbroken chain of documented comparisons connecting a measurement back to a recognized national or international standard.

Which organization maintains the primary mass standards for the United States?

Answer: NIST

NIST (National Institute of Standards and Technology) maintains the primary mass standards for the United States.

A scale that consistently reads 0.5 lb high on every load has which type of error?

Answer: Systematic error

A consistent offset in one direction is a systematic error, often correctable through calibration adjustment.

What is the tolerance for an ASTM Class 4 weight used in commercial weighing?

Answer: Looser than Class 1 but tighter than Class 7

ASTM weight classes are numbered 1 through 7, with Class 1 being most precise; Class 4 falls in the middle range.

When performing a linearity test on a scale, what is the technician evaluating?

Answer: Whether accuracy is consistent across the entire weighing range

A linearity test checks that the scale maintains acceptable accuracy at multiple points across its full capacity, not just at one load.

What is 'minimum capacity' on a weighing instrument?

Answer: The smallest load that can be weighed within the scale's accuracy class

Minimum capacity is the smallest load that can be weighed within the allowable error tolerance for that scale's accuracy class.

Which environmental factor most directly causes creep error in load cell-based scales?

Answer: Temperature changes in the load cell

Thermal expansion and contraction of load cell materials due to temperature changes is a primary cause of creep and zero drift.