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
During a teardown of the iPad Air and Microsoft Surface Pro 3 at the Medical Design & Manufacturing Show in Schaumburg, Ill., an engineer showed this "inflammatory" video about the dangers of maliciously mishandling lithium-ion batteries.
The Window Watcher stops the burglar before he does damage or enters the house. House alarm service companies set off alarms and call the service only after the burglar has damaged and entered the house.
If you’re designing a handheld device or industrial machine that will employ a user interface, then you’ll want to check out the upcoming Design News Continuing Education Center course, "Engineering Principles Behind Advanced User Interface Technologies.”
Brooke Williams of Texas Instruments explains how TI’s new TDA3x chip will help future vehicles “see” all around themselves.
It's been two years since the Mac Mini's last appearance on iFixit's teardown table, but a newly revised version joins Apple's lineup this week.
More:Blogs|News
Design News Webinar Series
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
9/25/2014 11:00 a.m. California / 2:00 p.m. New York
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.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 3 - 7, Engineering Principles behind Advanced User Interface Technologies
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.
Next Class: 10/28-10/30 11:00 AM
Sponsored by Stratasys
Next Class: 10/28-10/30 2:00 PM
Sponsored by Gates Corporation
Next Class: 11/11-11/13 2:00 PM
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