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 uncertainty (i.e. reporting smaller uncertainty than you should). For reference, the following documents recommend evaluating drift and included it in the uncertainty budget; EA-04/02 M: 2022 – Evaluation of the Unce ..read more

    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. reporting smaller uncertainty than you should). For reference, the following documents recommend or require stability (or instability) or drift is included in the uncertainty budget; EA-04/02 M: 2022 ..read more

    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 6 that you need to know. If you constantly struggle with probability distributions, keep reading. I am going to explain what are probability distributions, why they are important, and how they can help you when estimating mea ..read more

    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 Update Uncertainty Budgets What is a Significant Change Events that Prompt Updating Uncertainty Budgets How Often to Update Uncertainty Budgets   Scroll to keep reading or click one of the links above to go to that section.     When to Update Uncertai ..read more

    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 sources each time you estimate uncertainty is because they typically influence every measurement that you will ever make. Another reason you should use them in your uncertainty budget is they are common uncertainty contributors required by many accreditation bodies. Loo ..read more

    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 calibrator. In fact, I see this quite often. I have clients collect repeatability and reproducibility data for their uncertainty budgets and the results will have no variability. Typically, this is the result of one or more of the following factors: a lack of UUT ..read more

    Test Uncertainty Ratio Definition Test Uncertainty Ratio or TUR is a common term used in calibration. It is the ratio of the tolerance or specification of the test measurement in relation to the uncertainty in measurement results. According to the ANSI Z540.3 Handbook, the official definition is the ratio of the span of the tolerance of a measurement quantity subject to calibration, to twice the 95% expanded uncertainty of the measurement process used for calibration.     Measurement Capability Index In some parts of the world, test uncertainty ratio is known as measu ..read more

    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 links below to jump ahead to a particular section. What is Absolute Uncertainty Absolute Uncertainty Example How to Calculate Absolute Uncertainty How to Find Absolute Uncertainty Difference between Absolute and Relative Uncertainty How to Convert ..read more

    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, the decision rules that most of us have used to determine conformity are: If a result is within tolerance, it Passes; or If a result is out of tolerance, it Fails. Sounds familiar, right? Well, this is simple acceptance on an easy level that most of us can understand. Unfortunately, there are ..read more

    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, many experts, assessors, and accreditation bodies do a poor job of informing laboratories that: It is a significant contributor that should be included in uncertainty budgets, and What resources are ..read more