DAY 9 — Tolerance

What is tolerance?

A specified allowable range or limit within a requirement

What determines the meaning of tolerance?

The applicable specification standard method or requirement

Is tolerance a universal metrology term?

No

Should tolerance be used as a synonym for maximum permissible error?

No

What is a limit?

A boundary specified by a requirement

What is a specification?

A documented requirement or performance criterion

What is an accuracy specification?

A specified performance characteristic under stated conditions

How does VIM3 describe accuracy?

Accuracy is a qualitative concept and not a numerical value

What is an error limit?

An allowable error limit specified by the applicable requirement

What are acceptance criteria?

Criteria used to determine whether a result meets specified requirements

What is a decision rule?

A rule used when making a conformity decision while taking measurement uncertainty into account where applicable

What is MPE?

Maximum Permissible Error

What does MPE describe?

The extreme value of measurement error permitted by specifications or regulations for a given measurement measuring instrument or measuring system

What is an example of MPE?

MPE of ±0.5% of full scale

What is the difference between MPE and tolerance?

MPE concerns the permitted measurement error while tolerance is a specified allowable range or limit within a requirement

What is an example of tolerance in the infographic?

A specified allowable range of −0.5% to +0.5% of the indicated value

What is the key warning about tolerance and MPE?

Tolerance is not the same as MPE

Why should tolerance not be used to designate MPE?

Because VIM3 distinguishes tolerance from maximum permissible error

Why is measurement uncertainty important when judging a result near a limit?

Being close to a limit does not automatically determine whether a conformity decision is straightforward

When should measurement uncertainty be considered?

When relevant to the conformity decision

What does ISO/IEC 17025:2017 require regarding conformity statements?

A laboratory reports a statement of conformity using a decision rule that takes the associated level of risk into account

What is the pressure gauge example range?

0 to 100 kPa

What is the full scale of the pressure gauge example?

100 kPa

What is the accuracy specification in the pressure gauge example?

±0.5% of full scale

What is ±0.5% of 100 kPa?

±0.5 kPa

If the pressure gauge result is 99.6 kPa what should be considered?

The applicable decision rule and measurement uncertainty before reporting a conformity decision

Does a result that appears inside a limit automatically mean PASS?

No

What is a calibration red flag regarding PASS?

PASS without identifying the requirement or decision rule

Why is judging a result simply because it looks close enough a problem?

The result must be evaluated against the appropriate requirement and decision process

What should a calibrator know before making a conformity decision?

The requirement the relevant terms measurement uncertainty and applicable decision rule

What is the main mindset for tolerance decisions?

It is not only about the result but whether it meets the right requirement

What question should be asked when a result is close to a boundary?

What requirement decision rule and measurement uncertainty should be considered before calling it PASS?