# ISOBudgets blog by Rick Hogan

• ### Statements of Conformity and Decision Rules for ISO 17025

Introduction Statements of conformity and decision rules are two issues that have become a topic of discussion since the revision of the ISO/IEC 17025 standard. The new requirements have become more demanding, assessors are writing deficiencies, and people have a lot of questions about how to comply. So far, accreditation bodies are providing training […]

• ### How to Calculate Emissivity Uncertainty

Introduction Emissivity is a source of uncertainty that affects IR temperature (i.e. radiation thermometry). It should be included in uncertainty budgets for blackbody calibrators and IR Thermometers. However, many ISO/IEC 17025 accredited laboratories have not included emissivity uncertainty in their budgets because their lab personnel did not know how to evaluate it. Furthermore, […]

• ### Local Gravity: How to Calculate Yours in 3 Minutes

Introduction In Metrology, knowing your local gravity is important if you are performing comparison measurements that involve forces that are influenced by gravity. Established at the third General Conference on Weights and Measures in 1901, the standard gravity on Earth is 9.80665 m/s2, or 32.174 ft/s2. However, standard gravity only applies to an object […]

• ### Guard Banding – How to Take Uncertainty Into Account

Introduction There has been a lot of discussion on guard band and guard banding methods lately. Especially, with regard to statements of conformity and decision rules, and how you take uncertainty into account. This led me to look further into different guard banding methods. Currently, there have been a couple of recommended methods […]

• ### Uncertainty Budget Example

Need to estimate uncertainty? Then, you will need a calculator to create uncertainty budgets. In this guide, you a see an uncertainty budget example from our Simple Uncertainty Calculator. This guide will cover all of the elements that are part of an uncertainty budget and why you need them. Plus, you will see plenty […]

• ### How to Calculate Relative Uncertainty

Introduction Relative uncertainty is a concept that has been around for quite some time. It is commonly referenced in many documents but rarely covered in any detail. While relative uncertainties may seem simple, there are more use cases than just percent uncertainty such as parts per million uncertainty and uncertainty relative to a […]

• ### How to Calculate Air Buoyancy Correction with Examples

Introduction Did you know that air buoyancy is a significant contributor to uncertainty in measurement results? It affects the results of many tests and calibrations if you do not apply air buoyancy correction. Especially, measurements where a weight is involved, such as mass, force, pressure, and torque. Many labs are not taking this […]

• ### Calculating Effective Degrees of Freedom

When performing uncertainty analysis, it is important to calculate the degrees of freedom associated with the estimation of uncertainty. However, determining the total degrees of freedom is not simply adding together all of your independently calculated degrees of freedom. Instead, you must use the Welch Satterthwaite approximation equation to calculate the effective degrees of freedom. […]

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• ### How to Validate Uncertainty Budgets and Calculators

Introduction Has your assessor ever asked you if you validate uncertainty budgets? If so, I know your pain. It is frustrating! You have spent countless hours estimating uncertainty and creating uncertainty budgets just to have an assessor discredit all your hard work. Unfortunately, they are not wrong. They just want to make sure that […]

• ### How to Calculate Uncertainty With the Easy Uncertainty Calculator

Introduction Every laboratory needs an uncertainty calculator if they plan to get ISO/IEC 17025:2017 accredited. According to section 7.6 of the ISO/IEC 17025:2017 standard, every testing and calibration laboratory must evaluate measurement uncertainty and include all contributions considered to be significant. This means that you need to estimate uncertainty and create uncertainty budgets […]