# Uncertainty

• ### How to Calculate Drift Uncertainty

Introduction Drift is an important source of uncertainty. Typically, it is a significant contributor to uncertainty. As a result, laboratories should always include the drift or stability of their measurement equipment and(or) standards in their uncertainty budgets. Not including it in an uncertainty analysis is likely to result in an understatement of measurement […]

• ### How to Calculate Stability for Uncertainty

Introduction Stability is an important source of uncertainty. Typically, it is a significant contributor to uncertainty. As a result, calibration labs should always include the stability or drift of measurement equipment and(or) standards in their uncertainty budgets. Omitting it in an uncertainty analysis will likely result in an understatement of measurement uncertainty (i.e. […]

• ### Probability Distributions for Measurement Uncertainty

Introduction Probability distributions are an important part of measurement uncertainty analysis that people continually struggle with. Today, my goal is to help you learn more about probability distributions without having to grab a statistics textbook. Although there are hundreds of probability distributions that you could use, I am going to focus on the […]

• ### How to Perform a Repeatability Test for Estimating Uncertainty in Measurement

INTRODUCTION Performing a repeatability test is an essential part of estimating uncertainty in measurement. It is the most common experiment performed to collect Type A Uncertainty data. Additionally, most accreditation bodies require that you include repeatability data in your uncertainty budgets. However, many people have trouble with performing a repeatability test. They do […]

• ### How Often to Update Uncertainty Budgets

Introduction A common question people ask is “When should I update my uncertainty budgets?” or “How often should I update my uncertainty budgets?” Since the question so common, I decided to create an article to answer the question and offer advice. In this article, you will learn more about the following: When to […]

• ### 7 Sources of Uncertainty in Measurement for Every Uncertainty Budget

Introduction Have you ever wondered what sources of uncertainty in measurement to include in your uncertainty budget? I have, and I am sure that you have too. Today, I am going to show you 7 sources of uncertainty that should be included in every uncertainty budget. The reason you should include these uncertainty […]

• ### Repeatability is Zero, Here’s What to Do

When Repeatability is Zero Once in a while, you may encounter a scenario where your measurement repeatability is zero. This is common for certain types of measurements, such as: measuring a gauge block with a caliper, placing a calibrated mass on a scale or balance, or calibrating a handheld DMM with a multifunction […]

• ### Absolute Uncertainty – Everything You Need to Know

Introduction Absolute uncertainty and relative uncertainty are two terms used in uncertainty analysis to express how a reported uncertainty should be interpreted. The distinction between the two terms causes many people to be confused. So, I decided to make this guide to help answer common questions that people ask. Click any of the […]

• ### Simple Acceptance Decision Rule Examples

Introduction Simple acceptance is a decision rule that has been around for a long time (whether you knew what it was named or not). The best way to explain it is a set of rules used to determine whether a test or measurement result passes or fails based on the tolerance limits. Typically, […]

• ### 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 […]