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Tip of the Month |
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Tips for
using adapters when calibrating...
Back-to-back
reference accelerometers typically have a ¼-28 or 10-32 mounting
thread. Sensors under test (SUT) often require a different thread
interface. In these cases, mechanical adapters must be used to
allow for an appropriate mate. Unfortunately, adding this mechanical
adapter also adds mass and reduces stiffness between the reference
and SUT, which effectively reduces the mounted resonant frequency.
The result may be an out of tolerance condition in the upper
frequency range, say 10 kHz. The best practice is to avoid using
adapters if possible. As this may be unreasonable with certain
SUT's, the next best practice is to use as small of an adapter as
possible, with proper torque and ample silicone lubricant at each
mating point. Keep in mind that if you are having trouble comparing
calibration data at higher frequencies with the OEM or another
calibration laboratory, it is important to understand if both labs
are using similar mounting conditions. If not, this may be a
substantial contributor to measurement uncertainty.
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Newsletter Archive |
May 2007 - Basics of Accelerometer Function; How
Standards Link Together
June 2007 - Shear, Compression, Flexure; ISO 16063 Overview
July 2007 - Accelerometer Transduction Types (PE, PR, VC);
Laser Primary Calibration
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Which is a better sensing element... |
...Quartz or
Ceramic?
 Over
the years there has been a great deal of discussion over the merits
of selecting either quartz or ceramic as the sensing element for a
piezoelectric accelerometer. This month we'll review the benefits
of each, along with citing the specific applications where either
one or the other excels.... pun?
Click here to learn whether quartz or ceramic is best for your
application.
(http://www.modalshop.com/test_calibration.asp?ID=194)
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Basics of ISO-16063-21... |
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...Accelerometer Calibration via Reference
Standard
 ISO
16063-21 describes the most common embodiment of laboratory
accelerometer calibration. Utilizing either a back-to-back
(piggyback) reference standard or a specially constructed reference
standard accelerometer imbedded inside a precision calibration
exciter, this method provides the speed and simplicity of direct
sensor under test (SUT) mounting and calibration. Modern computer
controlled calibration systems can provide calibrations and prints
of calibration certificates in just a few minutes.
(http://www.modalshop.com/test_calibration.asp?ID=195)
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As always, your satisfaction is at the pinnacle
of our work. If you have questions that you would like answered,
please contact us and we'll be glad to help out. Your question may
even be featured in a future month...
Sincerely,
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Michael J. Lally
The Modal Shop
A PCB Group Company
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