Accelerometer Selection for Vibration Measurement | IEPE Accelerometer Guide

Selecting the right accelerometer for a vibration measurement application requires matching the accelerometer sensitivity, frequency range, resonant frequency, dynamic range, mass, and mounting method to the specific measurement requirements. Using an accelerometer with inappropriate sensitivity or mounting it incorrectly introduces errors that calibration cannot correct. This guide covers the key parameters for IEPE accelerometers used with multi-channel DAQ systems in noise and vibration analysis.

Key Specification Parameters

• Sensitivity — expressed in mV/g or mV/(m/s²). Higher sensitivity gives better signal-to-noise for low-amplitude vibration but limits the upper amplitude range. Typical values: 10 mV/g (general purpose), 100 mV/g (low-level precision), 1 mV/g (high-amplitude)
• Frequency range — the usable frequency range is bounded below by the low-frequency rolloff (determined by internal coupling capacitor) and above by approximately 1/3 of the mounted resonant frequency
• Mounted resonant frequency — depends on the accelerometer and the mounting method. Stud mounting gives the highest resonant frequency; adhesive pads and hand-held probes are significantly lower.
• Mass — accelerometer mass must be a small fraction of the structure mass at the attachment point. For lightweight structures, mass loading can shift resonant frequencies and affect vibration amplitude.
• IEPE current supply requirement — typically 2 to 10 mA constant current at 18 to 28 V compliance voltage

Mounting Methods and Their Effect on Frequency Response

• Stud mounting — highest mounted resonant frequency; requires drilled and tapped hole; best for permanent installations and precision measurement
• Adhesive pad (beeswax or cyanoacrylate) — good frequency response for temporary mounting; beeswax is reversible
• Magnetic base — convenient for ferromagnetic surfaces; limits mounted resonant frequency to typically 2 kHz
• Hand-held probe — lowest frequency response; resonant frequency typically below 1 kHz; for screening only

For combined acoustic and vibration measurement using the same DAQ system, PLACID IEPE accelerometers use the same BNC input connections and IEPE current supply as the measurement microphone preamplifiers. Mixed acoustic and vibration channels can be recorded simultaneously on a single PQ401, PQ801, or PQ1601 DAQ unit.

Accelerometer Calibration

IEPE accelerometers should be calibrated at regular intervals — typically annually — using a back-to-back comparison method with a reference accelerometer. ISO/IEC 17025 accredited calibration is available for IEPE accelerometers and provides the traceable sensitivity value and frequency response correction that are required for quantitative vibration measurement. The accredited sensitivity value should be entered into the measurement software to ensure that vibration levels are reported in the correct units. Hand-arm and whole-body vibration assessments require calibrated accelerometers with valid ISO/IEC 17025 certificates; the calibration documentation must be retained with the assessment records.