HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comments
View Comments: Newest First|Oldest First|Threaded View
tekochip
User Rank
Platinum
Re: Real measurement errors
tekochip   11/14/2013 9:32:41 AM
NO RATINGS
Very true!

 
A slightly different scenario, but I recall a technician sorting 10% resistors, trying to find a handful that were exactly the correct value.  He went through an entire bag and couldn't find any closer than 5%.  So much for Gaussian distribution.  Of course the reason was that all of the closer value resistors were already removed from the sample by the manufacturer to be sold as 5% resistors.


Ratsky
User Rank
Platinum
Other factors too!
Ratsky   11/13/2013 1:12:16 PM
NO RATINGS
There are other real-world factors that this analysis ignores.  One is calibration accuracy, another is calibration drift.  A typical calibration cycle is annually.  The day after an instrument is calibrated, the uncertainty can increase because of component aging, ambient temperature effects, etc.  Reality always makes uncertainty increase, often well beyond the simplistic approach of resolution; it's close to the concept of entropy. Resolution puts a LOWER BOUND on uncertainty, but no upper one!  That is the worst part of digital instrumentation, in that it misleads the user to trust the results far beyond what is merited.

Nancy Golden
User Rank
Platinum
Uncertainty in Measurements
Nancy Golden   11/13/2013 10:06:48 AM
NO RATINGS
Great article Jon - it is important to understand uncertainty in measurements so that you can understand whether or not a reading is really within tolerance. Understanding the tolerance that is acceptable (range of acceptable readings due to measurement uncertainty not only of test equipment but also the device under test) are both important to understand. Repeatability and reproducibility are also factors. Gage R & R is an important tool in this area. Uncertainty is also another reason to make sure your measurement equipment is in calibration. Thanks for the link to the Evaluation of Measurement Data: Guide to the Expression of Uncertainty in Measurement - it is an excellent resource.

SherpaDoug
User Rank
Gold
Real measurement errors
SherpaDoug   11/13/2013 9:27:38 AM
NO RATINGS
Real errors are rarely Gaussian.

Battar
User Rank
Platinum
2 Methods
Battar   11/12/2013 9:22:14 AM
NO RATINGS
Two equivalent methods to reduce uncertaincy:

1: Take a measurement from several sensors and average them

2: Take several measurements from one sensor and average them.



Partner Zone
Latest Analysis
Ever wanted your own giant robot? Three engineers did, and now they want to make 15-ft, fighting MegaBots a household name.
Here are 10 examples of the wide range of new technology on display at Pack Expo in Chicago earlier this month.
For decades, engineers have worked to combat erosion by developing high-strength alloys, composites, and surface coatings. However, in a new paper, a team at Jilin University in China turned to one of the most deadly animals in the world for inspiration -- the yellow fat-backed scorpion.
Freescale Semiconductor has rolled out a development system that aims to help automotive engineers create Ethernet-based multimedia hubs inside the vehicle.
Green energy is being billed as a way to make communities that are energy deprived more self-sustaining. So it makes sense to use natural materials to create devices that harvest this type of energy. That’s the idea behind a hybrid wind/solar energy harvester made of bamboo that’s been developed by UVM researchers.
More:Blogs|News
Design News Webinar Series
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Nov 17 - 21, Analog Design for the Digital World
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Last Archived Class
Sponsored by Littelfuse
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service