Category Archives: Worst Case

A Must-Have Book for Every Test Engineer

MediumTestEngineersBookCoverThe Test Engineer’s Measurement Handbook / How to Design Tests for 1st-Pass Success
by Van Brollini

Van Brollini’s new book is an essential addition to the test engineer’s library, as well as the library of any product manager.

The Handbook contains practical advice that is based on Mr. Brollini’s extensive experience with test development, including unique insights that I have not seen elsewhere, insights that will provide the test engineer with a quantum leap in productivity.

The test engineer will also appreciate the fact that Brollini’s methods — clearly presented as a series of rules, tips, and straightforward equations — are practical and cost-effective, illustrated by real-world examples throughout.

The Handbook’s teachings can be applied with basic math and spreadsheet tools, although Brollini does recommend Design Master™ for best efficiency, particularly for more advanced applications.

(I have known Van for many years, as he was one of the first engineers to adopt our Design Master software. From time to time he has offered suggestions for improvements, which were incorporated into the software.)

The Test Engineer’s Measurement Handbook is available through the DACI website.

-Ed Walker

Advertisements

4th Qtr 2011

(c) 2011 Design/Analysis Consultants, Inc.
Newsletter content may be copied in whole or part if attribution
to DACI and any referenced source is prominently displayed with the copied material

This Issue: NEWS BITE: Rising Sun Gets Snagged On Mountain And Breaks Apart! / DESIGN MASTER TIP: Minimizing Calculation Time / ANALYSIS: Why Do A Worst Case Analysis? / TECH TIP: Nice Overview of Considerations for External Components for Switching Regulators / MORE UNINTENDED CONSEQUENCES: Wind Power Kills Endangered Species / ANALYSIS QUIZ: Adjustable 3-Terminal Regulator Output Tolerance

NEWS BITE: Rising Sun Gets Snagged On Mountain And Breaks Apart!
Motorists cautioned to avoid area due to high temperatures.

First planet with two suns reported found
15 Sep 2011, NASA and World Science

DESIGN MASTER™ TIP: Minimizing Calculation Time

Do an initial run and check sensitivities. Thereafter set the variables to their respective worst case values to reduce calc time until the design is finalized. Then set the variables back to their full range for a final calculation to obtain probabilities for risk assessment.

ANALYSIS: Why Do A Worst Case Analysis?

 
TECH TIP: Nice Overview of Considerations for External Components for Switching Regulators
See “Power System Performance Requires The Right Actives And Passives” by Tim Watkins, 8 Sep 2011 Electronic Design

MORE UNINTENDED CONSEQUENCES: Wind Power Kills Endangered Species

In the Bay Area, when activists in the 1980s demanded a cleaner planet, the state responded with the Altamont Pass Wind Resource Area. The state-approved wind farm, built with federal tax credits, kills 4,700 birds annually, including 1,300 raptors, among them 70 golden eagles…

“There’s a big, big hypocrisy here,” Sue Hammer of Tehachapi Wildlife Rehab in Kern County said. “If I shoot an eagle, it’s a $10,000 fine and/or a vacation of one to five years in a federal pen of my choice.”

From “Energy in America: Dead Birds Unintended Consequence of Wind Power Development” by William La Jeunesse, 16 Aug 2011, FoxNews.com

ANALYSIS QUIZ: Adjustable 3-Terminal Regulator Output Tolerance

An LM317T regulator with 36V input is set for 24V nominal output, using 1/8W 1% 100ppm thick film resistors (10K and 549 ohms). The regulator must deliver 1A and operate from 0 to 50 C for 10,000 hours.


Q: What will be the approximate worst case output tolerance? (Answer will be posted in the next newsletter.)

3rd Qtr 2011

(c) 2011 Design/Analysis Consultants, Inc.
Newsletter content may be copied in whole or part if attribution
to DACI and any referenced source is prominently displayed with the copied material

This Issue: NEWS BITE: Mutant Singing Cantaloup Wins Karaoke Contest! / MORE UNINTENDED CONSEQUENCES: Hands-Free Faucets / DESIGN MASTER TIP: AC Rectifier Worst Case Analysis Made Easy / ART MEETS ENGINEERING: The Invisible Man / STATISTICAL DESIGN PITFALLS: Monte Carlo Is Not Worst Case Analysis

NEWS BITE: Mutant Singing Cantaloup Wins Karaoke Contest!

Freaky Robot Mouth Learns to Sing,”
Evan Ackerman, 13 July 2011, IEEE Spectrum

MORE UNINTENDED CONSEQUENCES: Hands-Free Faucets Harbor More Germs Than Standard Faucets

Details here.

DESIGN MASTER TIP: AC Rectifier Circuit Worst Case Analysis Made Easy

In our previous Newsletter we provided a pretty good estimate for the ripple current for the bulk capacitor in an AC rectifier circuit. But what if you have a large volume product and you need a full worst case analysis to ensure high reliability, but one that is not overly pessimistic so that you can minimize cost? Design Master can help you achieve that optimum balance.

As readers are aware, we’ve started to release some DMeXpert “fill in the blank” WCA templates to make the design engineer’s life a bit easier. One of these is our AC Bridge Rectifier Analysis (ACBR1 $19) which allows the designer to determine all of the worst case component stresses within a minute or two. The analysis includes the effects of source impedance Rs (such as transformer secondary winding ohms), which if present can be used to reduce capacitor ripple current requirements, hence reduce capacitor cost.

As those who have studied AC rectifier circuits are aware, this seemingly simple circuit has resisted for decades all of the attempts to generate a single-formula solution, until recently, which we’ve included in ACBR1. Based on Keng Wu’s article, “Analyzing Full-Wave Rectifiers With Capacitor Filters” (1 Jan 2010, Power Electronics Technology), Wu’s formula allows a straightforward circuit solution, greatly reducing computational time. So with ACBR1 you can just fill in the blanks, click Calculate, and let Design Master do the rest.

ART MEETS ENGINEERING: The Invisible Man

Engineers who work for the military are sometimes required to design clothing, equipment, or even entire shelters to be “invisible” to various detection means. Chinese artist Liu Bolin has a gift for applying such camouflage in a non-technological way, as seen below. Hint: If you can’t spot Liu, look for his shoes first.

From “The Invisible Man: Dragon Series,” Vurdlak, 28 June 2011, http://www.moillusions.com

Some more fascinating photos here and here.

STATISTICAL DESIGN PITFALLS: Monte Carlo Is Not Worst Case Analysis

A lot of folks like to let a simulator crank out “worst case” results, using Monte Carlo statistical methods. But as we’ve explained previously (“Design Master vs Extreme Value, RSS, Monte Carlo, & Simulation,” and “Design Master vs Monte Carlo“), this can be not only time consuming, but risky. For example, Monte Carlo can easily miss small but significant errors (see example below). In addition, if the Monte Carlo runs are improperly implemented (such as including temperature or other dynamic variables) you will likely obtain wildly inaccurate results.

The Design Master Advantage

Instead of statistical sampling, Design Master uses a top-down approach to achieve safer and more cost-effective results, by (a) detecting the extreme limits of performance, and then (b) using a proprietary probability algorithm to estimate how often those results will exceed the specification limits.

EXAMPLE

Design Master results at 2 samples/variable versus
Monte Carlo at 10,000 samples/variable, for the gain of an 8-variable filter

As can be seen, the Monte Carlo analysis detected a minimum of 8.42 versus the actual minimum of 7.86, a 7% error, and a maximum of 16.0 versus the actual maximum of 18.8, a 15% error.

Transient Voltage Suppressor (TVS) DMX Analysis File Released

Transient Voltage Suppressor (TVS) with Optional Steering Diode DMX Worst Case Analysis File
TVS1 $12.50
.

(DMX files are available free to Design Master™ Professional Edition users who purchased or upgraded DM not more than one year prior to the DMX file release date.)

The Transient Voltage Suppressor analysis determines whether a TVS avalanche diode and optional steering diode will (a) survive a specified surge voltage or current, (b) clamp the surge below a specified voltage limit, and (c) not clamp the normal operating voltage. Good for any TVS diode and steering diode; just fill in the blanks using data sheet values, and get an answer in a few seconds. TVS diodes are typically rated with 10x1000us current waveforms. Steering diodes are typically rated with line frequency half-sine current waveforms. When the applied surge has a different waveform, however, the TVS and steering diode ratings must be adjusted accordingly. In addition, the ratings must also be adjusted for pulse width and temperature. To help make the design engineer’s job a little easier, this analysis contains adjustment formulas for all of these factors. Also provides standard surge waveform requirements and helpful hints.

DMeXpert™ (DMX) files guide the user with pop-up instructions, component selection lists, standard part values, important formulas, and a variety of other tips that are activated when entering a Formula cell. It’s like having a design/analysis expert at your side.

AC Full Wave Bridge Rectifier DMX Analysis File Released

AC Bridge Rectifier DMX Worst Case Analysis File
ACBR1 $19

(DMX files are available free to Design Master™ Professional Edition users who purchased or upgraded DM not more than one year prior to the DMX file release date.)

This updated and easy-to-use analysis provides all of the key waveforms, voltages, and currents for the AC full wave bridge rectifier circuit, including the effects of source ohms. Output includes average input amps, rms input amps, input watts, Rs watts, capacitor rms amps, average load volts, average load amps, and output watts.

Capacitor Current

DMeXpert™ (DMX) files guide the user with pop-up instructions, component selection lists, standard part values, important formulas, and a variety of other tips that are activated when entering a Formula cell. It’s like having a design/analysis expert at your side.