What is accelerometer mounting resonance?

The mounting resonance is the natural frequency of the combined sensor-mounting system. It is always lower than the sensor's bare resonance because the mounting adds compliance. It determines the upper usable frequency range.

Why is the usable range only 1/3 of the mounted resonance?

Near resonance, amplitude response rises significantly (up to 30 dB at resonance). To stay within ±3 dB accuracy, the rule of thumb is to use only up to 1/3 of the mounted resonance frequency.

Free Engineering Tool

Accelerometer Mounting Resonance Calculator

Calculate the usable frequency range of your accelerometer based on mounting method. Compare stud, adhesive, magnet, and probe tip mounting effects on measurement bandwidth.

Stud ~30 kHz Adhesive ~20 kHz Magnet ~7 kHz Probe ~2 kHz

Sensor Resonant Frequency (kHz, from datasheet)

Sensor Mass (grams)

Mounting Method

Accuracy Target

Results

Usable Frequency Range

—

Mounted Resonance

—

Sensor Bare Resonance

—

Resonance Reduction Factor

—

Accuracy Band

—

Comparison — All Mounting Methods (Usable Range)

Mounting Resonance Effect

Every accelerometer has a resonant frequency specified for ideal (stud) mounting. When using less rigid mounting methods, the system resonance drops because the mounting adds compliance (spring effect).

Where k is the mounting reduction factor, typically:

Mounting Methods — Typical Resonance Values

Mounting Method	Typical Mounted Resonance	Factor k	Usable Range (at ±3 dB)
Stud mount	28–32 kHz	0.90–0.95	~10 kHz
Thin adhesive layer	18–22 kHz	0.60–0.70	~6–7 kHz
Adhesive pad (thick)	12–16 kHz	0.40–0.50	~4–5 kHz
Flat magnet	6–8 kHz	0.20–0.25	~2–2.5 kHz
Two-pole magnet	3–5 kHz	0.10–0.15	~1–1.5 kHz
Probe tip / hand-held	1.5–2.5 kHz	0.05–0.08	~0.5–0.8 kHz

ℹ️ Rule of Thumb: Use only up to 1/3 of the mounted resonance frequency for measurements within ±3 dB accuracy. For ±1 dB, use only 1/5. For highest accuracy (±0.5 dB), use only 1/10.

Practical Recommendations

Route-based monitoring: Magnet mount is common — acceptable for frequencies up to ~2 kHz (120,000 CPM)
Permanent monitoring: Always use stud mount for maximum bandwidth and repeatability
Quick checks: Probe tip is okay for low-frequency measurements (1× and 2× on slow machines)
Bearing analysis: Requires stud or thin adhesive for high-frequency envelope detection

⚠️ Important: Sensor mass should be <10% of the structure mass at the measurement point. Heavy sensors on lightweight structures reduce mounted resonance further and can alter the vibration being measured.