The Ommatidia Q2 is an FMCW Laser RADAR-based, multibeam vibrometer that acquires 65 simultaneous points arranged in a line. For random or ambient excitation, parallel acquisition ensures all points are measured concurrently, avoiding phase inconsistency associated with scanning approaches. Relevant specifications:

• 65-point simultaneous vibrometry; selectable sampling up to 40 kHz; velocity range ±15.5 mm/s.
• Integrated triaxial accelerometer: 2,000 Hz bandwidth, 4,000 Hz sampling, 22.5 µg/√Hz noise, enabling discrimination of environmental and instrument vibrations such as traffic, wind, and internal fans.
• Full-HD RGB camera (1920×1080) with autofocus for alignment and documentation.
• IP54 ruggedization and atmospheric compensation for pressure, temperature, and humidity.
• GigE connectivity, GPS sync, analog I/O, digital output; control via Ommatidia Atelier; data in HDF5.
• Elevation microscanner for dense vertical sampling when required, and a long-acquisition static mode for stability and spectral resolution.

Target: Geothermal system chimney, concrete and hollow, approximately 2 m × 1 m × 35 m.

• Stand-off: Approximately 25 m; measurement line oriented vertically along the facade.
• Surface preparation: None required.
• Mode: Long-acquisition static vibrometry for continuous time series.
• Acquisitions: Three runs of 300 s each on the same vertical line. Procedure: 1) Align the vertical 65-point beam line using the RGB camera and autofocus. 2) Configure long-acquisition static vibrometry to prioritize temporal stability and low-frequency resolution. 3) Record simultaneous Q2 vibrometry data and the internal accelerometer time series. 4) Post-process frequency spectra to compare structural response against environmental and instrument signatures.

The dynamic characterization of buildings is challenging due to very low amplitudes and dominant frequencies often below 10 Hz. Controlled excitation is rarely practical at the asset scale, making ambient excitation analysis a preferred route. This application note evaluates the Ommatidia Q2 multibeam Laser Doppler Vibrometer for remote, non-contact capture of real building vibrations under ambient excitation. Keywords: laser vibrometry, buildings, ambient excitation, structural monitoring

Spectral analysis revealed peaks at 5 Hz, 10 Hz, and 110 Hz present in both vibrometer and accelerometer spectra, indicating non-structural origins. The 110 Hz component aligns with internal cooling fans. The 5 Hz and 10 Hz peaks are consistent with ground-borne excitations from the urban environment. A distinct 1.7 Hz peak present in the vibrometer data but not mirrored by the accelerometer was attributed to the chimney’s structural response. Key takeaways:

• Ambient-only excitation is sufficient for identifying low-frequency building modes.
• The integrated accelerometer is pivotal for source discrimination, isolating true building dynamics from environmental and instrument-borne vibrations.
• Parallel 65-point capture provides instantaneous, phase-consistent spatial insight along the measured line.

Site selection: Position on stable ground with clear line of sight and minimize local vibration coupling to the instrument using a rigid tripod and isolation pads as needed.

• Configuration: Use long-acquisition static mode for low-frequency targets below 10 Hz. Calibrate sampling rate and record length to achieve the desired spectral resolution.
• Validation: Compare vibrometer spectra with the internal accelerometer to reject environmental or instrument peaks.
• Documentation: Use the RGB camera for alignment records and repeatability. Store data in HDF5 for traceable workflows.

Accelerate remote, non-contact diagnostics of buildings and civil assets. Request a demonstration or speak with an applications engineer. Contact our team: https://ommatidia-lidar.com/products/