Decoding the Accelerometer Specification Sheet

Remember the famous line from Romeo & Juliet, “What’s in a name? That which we call a rose by any other name would smell as sweet…”  How about when it comes to accelerometers… is it the same?  Is a rose still a rose still a rose?  Well… as you might imagine… there is a great deal of variance.  A survey on specification sheets sheets for a similar accelerometer from 5 different sensor manufacturers indicates a disparity of what vendors consider as "standard" specifications.  5 out of 5 Manufacturers listed...

5 of 5 Manufacturers Listed:  Reference Sensitivity, Acceleration Range, Frequency Resp./Res. Freq., Broadband Resolution, Transverse Sensitivity, Shock Limit, Operating Temp Range, Temperature Response, Supply Voltage/Current, Output Impedance, Output Bias Voltage, Housing Material & Connector, Sealing, Dimensions/Weight/Mounting

4 of 5 Manufacturers Listed:  Amplitude Linearity

3 of 5 Manufacturers Listed:  Discharge Time Constant, Warm-Up Time, Sensing Element Material, Sensing Element Style, Vibration Limit, Base Strain Sensitivity

2 of 5 Manufacturers Listed:  FS Output Voltage, Grounding, Output Polarity, Thermal Transient Sensitivity

1 of 5 Manufacturers Listed:  Spectral Noise, Magnetic Sensitivity

0 of 5 Manufacturers Listed:  Amplification Factor, Acoustic Sensitivity, Storage Temperature Range, Mounting Error, Sensitivity Stability, Damping, Mounting Surface Preparation, Supply Current Sensitivity

A quick search on GlobalSpec shows 190 possible vendors for accelerometers.  That makes quite a bouquet of roses!  To start an educated comparison we can look at specifications right?  Are they all really the same?  Good luck finding an apples to apples comparison.

To help demystify the accelerometer specification world, Mr. David Lally, PCB Vice President of Engineering regularly provides education on accelerometer performance and specification.   Click here to view his presentation entitled, “Decoding an Accelerometer Specification Sheet… What Sensor Manufacturers Don’t Tell You!” helps to uncover many of the quirks, inconsistencies and little secrets of the industry… Keys to his advice include avoiding suspect product specifications listed as “typical”, understanding the various ways of defining and measuring common specifications like noise floor, and reviewing the history/capability/certifications of the manufacturer.  They should be experts in sensing technology, ISO9000 certified manufacturing (with QS/AS certification as appropriate), ISO17025 certified in calibration, as well as experts in various means of calibration and specification testing.

In the end, he preaches caveat emptor - let the buyer beware!  Some manufacturers often smooth specifications, omit tolerances and skip quality testing to increase yields and profitability at the expense of product performance.  Your best strategy is to be armed with the knowledge of how accelerometers work work and choose a vendor you can trust.