| Tip of the
Month |
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Interlaboratory Comparisons
When participating in inter-laboratory comparisons (ILC), be
sure the test definition is clear from the start and
calibrations are performed at the same frequencies. This
avoids the possibility of additional error due to
interpolation. For example, if the ILC calls for
reporting results at 5, 7 and 10 Hz and the participating lab
calibrates at 5, 8 and 10 Hz, interpolation must be used to estimate
the sensitivity at 7 Hz. If this falls in a region where the
sensor's frequency response is not flat, this can lead to an
interpolation error on the order of 1% which could cause the
participating lab's results to fall outside acceptable
criteria. |
| Newsletter
Archive |
ICP Triaxial Accelerometers Aid Vehicle Field Diagnostics; New
Transverse Methods of Calibration
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Proficiency
Deficiency |
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 You
do it. I do it. Everyone does it. What is
"it"?...we make mistakes. In the technical and business world,
quality systems have a regularly administered audit component to
provide a means for testing and finding these "opportunities for
improvement". The Modal Shop's calibration product group
manager, Mr. Eric Seller, recently attended a regional meeting of
NCSLi in Ann Arbor, Michigan. Despite the region's current
economic woes and the plight of the American auto industry, the
meeting found an upbeat tone with a full house of around 50
metrology practitioners. Of particular interest and
usefulness, Eric brought back an excellent presentation by Mr.
Robert Knake of A2LA addressing the
"Most Common Deficiencies" found during the ISO17025 assessment
audit process. We thank Mr. Knake and the A2LA organization
for the approval to reprint his presentation in this
newsletter. As an ongoing educational topic, for the next few
months we'll discuss a few of the major deficiencies and present the
hows and whys of avoiding or addressing them within your own
accelerometer or microphone calibration program. To start off
the discussion, let's look at the number 10 deficiency: Infractions
in ISO17025 Section 5.9, Assuring the Quality of Test and
Calibration Results...
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| Got your TEDS
on? |
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 Have
you ever... stared at your accelerometer (with its arcane model
number neatly etched), only to wonder about the useful information
like: What's the high or low frequency point? What's the exact
sensitivity? Or when was this last calibrated? Without
reflecting on sanity, you wish, "...if only this little guy could
talk." Well it turns out that now they can. Sensors with
Transducer Electronic Data Sheet (TEDS) capability provide a
standardized means for various types of sensors to "tell" the data
acquisition system (or test personnel) their specifications on
demand. At the International Modal Analysis Conference (IMAC) in
Orlando this year, the Modal Shop's Structural Test Product group
manager, Mr. Marco Peres, gave a talk about the history and current status
of the TEDS in the dynamic sensor industry. While
estimates of the number of TEDS accelerometers in service are
approaching 200,000 units, there are many test professionals who are
still learning...
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| We appreciate your
interest and are glad to be providing you information on a regular
basis to help with your dynamic testing and calibration needs.
If you have any questions you would like answered or have a topic
you would like to see covered, please contact us and we'll be glad
to help out.
Sincerely, |
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Michael J. Lally The Modal Shop
A PCB Group Company
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