To reduce schedules, prototype cycles are often randomly slashed. Eventually the time and resources are needed and create cost and schedule over runs. We need to recognize that prototypes exist to help us learn about our product. If we use a risk based test strategy approach, we can test at lower levels to gain the required understanding. Then, we can confirm our learning with the higher level, system prototypes.

Just 4 minutes and 19 second long. To me, a prototype does include bench testing at lower levels as long as it includes the relevant functionality to represent the area for learning. [Read more…]

by Carl S. Carlson 2 Comments

Understanding FMEA Failure Modes – Part 1

Why Describing the Mode of Failure is Essential

Do you know why we ask for the “mode” of failure when performing FMEAs? This article will provide theory and practical examples of defining failure modes, and highlight an application tip that can improve your FMEA effectiveness.

“I haven’t failed, I’ve just found ten thousand ways that don’t work”
Thomas Edison

[Read more…]

by Anne Meixner 1 Comment

The Test Attributes of Controllability and Observability

If a tree falls in a forest with no one around to hear it, does it still make a sound?

If a fault occurs in a combinational circuit but its masked at the outputs is it still a fault?

If you can’t excite a fault from the circuit inputs does it really exist?

If you can’t propagate a fault to an output pin, does it matter?

In assessing an integrated circuit’s testability engineers consider the concepts of controllability and observability. In these specific characteristics of testability came up often the academic test literature of the 1970’s and 1980’s. The challenge back then was automatic test generation and fault simulation. [Read more…]

by Perry Parendo Leave a Comment

Model Building

Statistical Model Building

Model Building is a key theme for several advanced techniques. It boils down to creating an equation. Done well, one can predict and forecast how things will behave. Creating understanding reduces product risk and increases the chances for success.

Just 3 minutes and 9 second long, lets get the basics of model building to improve your understanding of how a system works. [Read more…]

by Carl S. Carlson 7 Comments

FMEA Q and A – System-Level Functions

FMEA Q and A

In this question, a reader asks how to define system-level functions, and how they are different from subsystem and component functions.

“A prudent question is one-half of wisdom.”
Francis Bacon

[Read more…]

by Perry Parendo 6 Comments

ANOVA Calculation Example

An Explanation and an ANOVA Calculation Example

Our white paper regarding t-test calculations has been very popular. Those that use the t-test tool regularly have commented “I finally understand what it is all about.”

The natural question they ask me next is “have you done anything with the F-test?” It is another common tool and one that is equally misunderstood.

Due to popular request, here is our attempt at explaining the F-test tool, in the two possible methods of use. [Read more…]

by Carl S. Carlson Leave a Comment

Understanding Functions – Part 2

Problems and Solutions

Do you consider yourself an FMEA beginner or are you more experienced? Challenge yourself with these problems about FMEA functions, and see how you do. One of the best ways to learn is by pondering application problems and seeing of you can solve them.

If you haven’t yet read last week’s article Understanding FMEA Functions – Part 1, it would be a good idea to read it now, as the questions are based on that article.

[Read more…]

by Anne Meixner Leave a Comment

Labor Saving DFT: Built-In Self-Test

In honor of Labor Day, I thought I would jump over to the Built-In Self-Test (BIST) wing of the DFT Castle.

I will provide you with a quick tour. Then when you hear the term in a meeting you can follow along and ask a few questions.

BIST saves labor for the Automatic Test Equipment (ATE).

Though there’s no free lunch. BIST does require an engineer to labor—someone has to design it specific to the device under test (DUT). [Read more…]

by Dennis Craggs Leave a Comment

DOE Supports World Class Quality

This is an example of a practical DOE that was used in the development of a manual window mechanism for a truck application. A similar process can be used for current mechanical and electrical design and development projects. In this article, you will see that the DOE method:

is superior to the design-test-fix cycle
builds knowledge of which factors are important to product performance
quantifies the effect of a combination of factors
allows performance prediction

[Read more…]

by Perry Parendo Leave a Comment

The Basis of Design of Experiments is Comparison

A t-test Example

The basis of DOE analysis is comparing two samples. This methodology can be used just as well for changing one variable or more than one variable as in DOEs. Comparison of means is as simple as the t-test.

Some people initially feel intimidated considering the connection of DOE with statistics. Once they understand it in simple terms, the topic comes together for them.

So let’s see if we can accomplish that for you now. [Read more…]

by Carl S. Carlson 1 Comment

Understanding FMEA Functions – Part 1

The Essence of the Item

What is the essence of properly defined FMEA Functions? More than half of FMEA practitioners miss a key element when defining FMEA functions. This first article in the FMEA Definitions and Concepts Series will discuss functions and their application in FMEAs.

“A perfection of means, and confusion of aims, seems to be our main problem.”
Albert Einstein

[Read more…]

by Anne Meixner Leave a Comment

A Primer on Design For Test

In a previous article I alluded to Design for Test (DFT) by mentioning a specific example.

The techniques have been around for decades. Just how long ago though?

I searched on “Design for Test” in the IEEE paper data base; the search resulted in 760 references the oldest being 1983.

Hmm there had to be earlier papers? So next I plugged in the key words “Design For Testability.” This time a list of 4,235 references appeared, the oldest one published in 1978. [Read more…]

by Carl S. Carlson 2 Comments

FMEA Q & A – Medical Devices

3 Medical Device Questions

FMEA Q & A

In these series of questions, a reader asks about whether system FMEAs in the medical device industry should include human interactions, and the difference between system and application FMEAs.

“The art of proposing a question must be held of higher value than solving it.” Georg Cantor

[Read more…]

by Anne Meixner 1 Comment

How to Test Clocked Circuits

What happens when you power up an electronics device with clocked circuits?

Well you have a clock running and you have clocked circuit elements, also known as sequential circuits. Latches, registers, basically any “memory” element. What could interfere with testing?

Do you know the state of that “memory element” when you start?

Heck No!

That’s a problem. [Read more…]

by Dennis Craggs 1 Comment

Reliability Test Validation and Product Verification

Working with product engineers to develop a reliability test early in a program can be a satisfying experience. My interactions with the product engineers are the most fruitful when there is mutual respect. I ask the product engineer questions about his goals, the product features, the supplier, and rely on his product expertise. I like to examine prototype parts and review an engineering drawing or the circuit diagrams.

A good example was when a product engineer, let’s call him Jim, approached me to develop a safety switch reliability test.

[Read more…]