How to calculate combined uncertainty for NABL/ISO/IEC 17025:2017


To calculate the uncertainty of your measurements, you'll need to find the best estimate of your measurement and consider the results when you add or subtract the measurement of uncertainty.


After measuring the individual uncertainty due to type A and type B, the combined uncertainty (Uc) is calculated as follows; Uc = √ (U12 + U12 + U12+……) Where; U1, U2, U3 etc are uncertainties calculated with same units       

Another method of combining uncertainty with different units of measure is fractional uncertainty.

1.     Identify the equation

2.     Calculate the fractional uncertainty for each contributor

3.     Calculate the combined uncertainty

4.     Convert the result to the desired unit of measure.

The quantities that affects the measurand may not have a direct one to one relationship with it. Indeed they may be entirely different unit altogether. For example a dimensional laboratory may use Steel gauge block for calibrating measuring tools. A significant influence quantity is temperature. Because the gauge blocks has a significant coefficient of expansion, there is an uncertainty arises in their length due to uncertainty in temperature units. In order to translate the temperature uncertainty into uncertainty in length units, it is necessary to know how sensitive the length of the gauge blocks is to temperature. In other words a sensitivity coefficient is required

Instead of being calculated from the function f, sensitivity coefficients ∂f / ∂xi are sometimes determined experimentally: one measures the change in Y produced by a change in a particular Xi while holding the remaining input quantities constant. In this case, the knowledge of the function f (or a portion of it when only several sensitivity coefficients are so determined) is accordingly reduced to an empirical first-order Taylor series expansion based on the measured sensitivity coefficients.




Comments

Post a Comment

Popular posts from this blog

RETAIL SECURITY GUARDS

Image
  RETAIL SECURITY GUARDS SERVICE COVER: ·          Loss Prevention Training and Awareness ·          Special Event (Tent Sale) ·          Coverage Parking Area Patrol ·          Site Surveys/Risk Assessments ·          24/7 Dispatch and Supervision ·          Crowd Control ·          Closed Circuit ·          Monitoring Access Control   Security Services can provide the right plan of action to put a stop to theft and shrinkage with retail security services. Retail shopping stores are facing increasing need for superior security. Thieves routinely fill their bags with merchandise and exit the store undetected. Employee theft can occur right under management’s nose. Fortunately, Rapid Security Services can provide the right plan of action to put a stop to theft and shrinkage with retail security services. The need for superior retail security is increasing, and Rapid Security Services is equipped to handle the task. Every retail premises has Site Security issues o
Read more

FIRE SAFETY

Image
  Fire safety is the set of practices intended to reduce the destruction caused by Fire. It includes those that are intended to prevent ignition of an uncontrolled fire, and those that are used to limit the development and effects of a fire after it starts. All of our work forces are trained to handle all fire fighting equipments and thus in case of emergency they need not depend on fire brigade to extinguish the fire to avoid destruction.   The fire is a common and serious emergency situation that security has to deal with. As a security guard, your main duty is to protect people and property but the fire can destroy both in a minute. You should manage and look over the fire hazard on your site. Mostly, the security guards are the first person to detect in the early stage of fire. In the case of fire, you have to know how to react quickly and confidently. So, you should know the available types of fire equipment and their location on your site. Not only this but also you must
Read more