TMS Square sensor & calibration tips                                          Your one-stop sound & vibration shop

Welcome to issue #20-
If you are new to our newsletter, please enjoy this short communication, share it with a colleague and have a look at the archive links below where you'll find all the back issues with their wealth of information.  We're glad to have you on board!  
Accelerometer Temp Extremes
Tip of the Month
Use a transfer standard
Consider using a laser calibrated transfer standard accelerometer to calibrate your calibration system's working standard each year.  This allows you to keep your system operational full time, just sending the transfer standard in each year and reduces your uncertainty.  The Modal Shop now has ISO 17025 / A2LA certified laser primary calibration services available to support this directly in technology center in Cincinnati.
Quick Links
Newsletter Archive
New developments in accel cal; Introduction to industrial accels
sensor & cal tips #17 -
Improving your accel calibration reference measurement at low frequencies; ICP® options
sensor & cal tips #18 - Why calibrate; Accelerometer selection considerations
sensor & cal tips #19 - Linearity and the small world
Archived sensor & cal tips - all the back issues

Motion in the ocean...

(and low frequency calibration)
Cruise ShipIt is that time of year again when those of us in the northern climates let our thoughts drift from the chill of the winter season (including this darn economy!) to dream of sunshine and tropical breezes.  One way to feed this need is a spring break adventure on an ocean cruise.  The ships are a fun ride with a little bit of roll at elevated sea states (in addition to being a great way to corral and entertain my teenagers during spring break).  The period (3 to 8 sec) of some midsized ship can be in a nauseous range of 0.13 to 0.33 hz, while the period of the largest (about 10 sec) provides an extremely low natural frequency of 0.1 hz and very little motion at normal sea states.  Just as travel with teenage children presents its own unique challenges, measurements and calibrations at these very low frequencies do too. A few months ago we introduced an innovative new technique for very low frequency calibration.  This month we will discuss this new low frequency calibration method in more detail as presented through our recent IMAC paper... 
Click to read more about low frequency calibration(
Cable considerations and constant current level
CableCapacitanceOperation over long cables may affect frequency response and introduce noise and distortion when an insufficient current is available to drive cable capacitance.
Unlike charge ouput systems, where the system noise is a function of cable length, ICP sensors provide a high voltage, low impedance output well-suited for driving long cables through harsh environments.
While there is virtually no increase in noise with ICP sensors, the capacitive loading of the cable may distort or filter higher frequency signals depending on the supply current and the output impedance of the sensor...
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.
Mike Lally signature
Michael J. Lally
The Modal Shop
A PCB Group Company