Example Component Analysis
December 10, 2002
The component I have chosen to evaluate is the accelerometer, which is essential for our characterization testing. The whole basis for drop shock testing is obtaining G-values felt by the chips through judicious testing. The industry standard for testing G-values is to use accelerometers to measure these values. Therefore, before any prototyping or testing can be done properly, it is important to establish the validity of the equipment used to measure these values.
I began by emailing Charlie Paynter the head engineer of our project and finding out which accelerometers would initially be available for our use. He responded that we would be using the Endevco 2222C. I looked up the company’s website and downloaded the necessary spec sheet. I then consulted with Charlie as well as my other teammates and determined the requirements for any possible accelerometers to be used. The primary requirements were as follow:
· Mount flat onto the area of the smallest chip (square mounting surface with sides = .4375 in.) we would be using in testing and also have a maximum thickness of .2 in. (arbitrarily determined from phones being used in testing and current accelerometer).
· Have a Shock Limit of no less than 5000g. Expecting values that could be as high as 10000g, higher values would be clearly preferable.
Some secondary considerations were:
· Having as low of a mass as possible to reduce mass loading during the drops. With phones as light as 68 grams, accelerometers with large masses could have a significant effect on drop speed and G-values.
· Simple mounting would be preferable due to the number of phones being used and number of tests being done.
· Temperature and Humidity variation should be kept to a minimum. Although lab conditions should be close to ideal, it is a good idea to remove all possible causes for error.
· High Sensitivity and robust Amplitude Linearity are good checks to do for the quality of the accelerometer. A component that exhibits these traits is likely to produce quality data.
Keeping these requirements in mind I consulted the Thomas Register to find companies that make accelerometers which meet our needs. An initial search provided 113 companies that produced accelerometers. After reading through several websites and finding that most were far to large, I modified my search to only include miniature accelerometers. This subcategory only contained two companies, neither of which was Endevco, the maker of the miniature accelerometer that we would be using. I went back to Endevco’s website and looked for other distinguishing features of their 2222C model. I found that the model utilized Piezoelectric technology. Using this fact, I went back and searched for companies that made Piezoelectric accelerometers and found 13 entries. After browsing catalogues from all the available companies I found only three sensors that could meet our rigid limitations. These were:
Upon consultation with Randy Matten, the technician in charge of operating the accelerometers and associated equipment during our testing, I learned that Endevco was the Industry standard for small electronics testing and was also the most well known. Here is the data I was able to collect for the three accelerometers I had chosen.
Information from Web Catalogues:
1) Endevco 2222C
2) Dytran 3225F1
3)GS Sensors G72A
Important characteristics are highlighted.
Information gathered through correspondence.
Endevco 2222C: $700 for accelerometer and calibration tools
GS Sensors G72A:
Information for Dytran 3225 obtained from email to firstname.lastname@example.org
Information for GS Sensors G72A obtained through phone call to Terry Smith.
Here is a table summarizing the pros and cons of each accelerometer:
For our application the Endevco 2222C is the best option. It provides the highest shock limit and smallest dimensions and mass of all accelerometers surveyed. It also has the tremendous advantage of being on-site thus eliminating lead time. If data cannot be made more robust through refined testing methods, further research may be necessary.
Keywords – Accelerometers, Piezoelectric, Miniature, Drop, Shock
Email – Charlie Paynter, Qualcomm
Phone Calls – Terry Smith, GS Sensors, (888)-455-4326