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Tip of the Month: Equipment Rental Helps with Short-Term Needs
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Technical Exchanges
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October 26-30
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October 28-30
Novi, MI
February 2-5, 2015
Orlando, FL
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Quick Links
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ISO TC 108 - Mechanical vibration, shock and condition monitoring
ISO TC 108/SC 3 - Use and calibration of vibration and shock measuring instruments
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Previous Newsletters
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Know Your Standard: ISO 16063; University of Buffalo Calibrates Seismic Sensors for Earthquake Simulation
Potentially Confusing Uncertainty Contributors; Pressure Calibration Techniques
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Why the Word 'Hermetic' is Important to
Your Piezoelectric Sensors
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One of the most significant investments for  manufacturers of quality dynamic piezoelectric sensors (force, pressure, vibration) is the machinery to ensure a hermetic seal of the transducer casing from contaminants in the outside world. Specifically, this means the technology and equipment to produce the glass-to-metal seal in a hermetic signal cable connector, and also the laser welder to seal the finished transducer casing.
The sensor sealing is critical due to the high impedance signal path at the heart of the piezoelectric crystal transduction. A typical piezoelectric sensor signal starts as a high impedance charge collected...
modalshop.com/calibration.asp?ID=1018
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Frequently Asked Questions:
When An Accelerometer Fails Calibration
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Q: I use this sensor on a daily basis, and haven't noticed a difference in any of my measurement results. Could it be that signals I am measuring do not have significant activity in the "failure" frequency range or that my measurements are not sensitive enough for me to have picked up on differences between the two sensors?
A: Yes, it is quite possible. It seems you have the benefit of some quantitative information in the calibration results, i.e., "X%". If the usual behavior of the sensor was 4.9% at "Y" Hz and is now 5.1% (crossing a 5% criteria for an acceptable calibration), you would have a 0.2% change in your sensitivity, and your data. This may or may not be detectable, depending on the predictability of your measured structure's behavior...
modalshop.com/calibration.asp?ID=1017
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Blast from the Past: Improved Low-Frequency
Accelerometer Calibration
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Discussion about accelerometer calibration often refers  primarily to the measurement of voltage sensitivity across a frequency range. The most common way to calibrate accelerometer sensitivity is by comparison to a reference transducer, generally another accelerometer designed to have stable low noise sensitivity in the conditions of calibration. Comparison methods are performed by back-to-back measurements, typically as a stepped sinusoid across an appropriate frequency range. The Sensor Under Test (SUT) is mounted...
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Thanks for joining us for another issue of "Dynamic Sensors & Calibration Tips". As always, please speak up and let us know what you like. We appreciate all feedback: positive, critical or otherwise. Take care!
Sincerely,
 Michael J. Lally A PCB Group Company |
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