VIBRALOG Seismograph for Passive Seismic Acquisition Nakamura method

24 bit seismograph for passive seismic activity, particularly indicated for recording micro-earthquakes or seismic vibrations. The data acquisition methods (timed or with trigger threshold) are set through the software easily and quickly. Equipped with graphic display, keyboard, memory support of Secure Digital (S.D.) type and internal battery, seismograph VIBRALOG is particularly easy to use also in less favourable environments and conditions.
Thanks to the MAE data acquisition and conversion card, based on one single A/D signal converter for each inlet channel (SST technology), it allows to obtain the best possible resolution when acquiring the data for each single inlet channel and it allows to record and graphically visualize up to 4 channels coming from seismic sensors (with single component or tridimensional).
Thanks to its dynamic characteristics, the instrument is particularly suitable to determine the resonance frequency of the site, through the H/V ratio method and to acquire transitional events (caused by natural seismicity or human activities) with the purpose to calculate the maximum speeds of the stresses suffered by a structure.

SPECIFICATIONS 

- Converters: 24 bit resolution, sigma- delta technology

- Dynamic range: 144 dB (theoretical)

- Maximum distortion: +/-0.0010%

- Band width: 2Hz-30KHz

- Common mode rejection: 110dB at 60Hz

- Diaphony: -120dB at 20Hz

- Noise threshold of the programmable amplifier: 27nV

- Maximum range of inlet signal: +/-5V

- Inlet impedance at 1000 samples/second: 20MΩ

- Amplification levels: 0dB, 6dB, 12dB, 18dB, 24dB, 30dB, 36dB that can be set singularly for each channel

- Anti-alias filter: -3dB, 80% of Nyquist frequency, -80dB

- Pre-trigger time: from 1% to 50% of the event duration

- Sampling frequencies 100, 500, 1000, 2000 samples per second; 250c/s in continuous recording

- Sampling intervals: 0.5, 1.0, 2.0, 4.0, 10.0 ms

- Length of the event recorded: from 512 to 21504 samples (215sec. at 100c/s or 10.7sec. at 2000c/s). Depending on SD capacity in continuous recording

- Channels: 3 + 1 optional. Possibility to use from 1 to the maximum number of channels installed for each acquisition

- Test on instruments: only in the laboratory. Internal self-calibration of the converters prior to each acquisition

- Digital filters: selected automatically based on the sampling frequency

- Data storage: on removable SD memory, up to 2 GB

- Trigger: 10 threshold levels for each channel (minimum 8mV – max. 5V). Up to 3 coincidence combinations between channels

- Data format: SEG-2 standard (32-bit long integer), BIN convertible in ASCII

- Power supply: 12V DC. Internal batteries of 2.5Ah. Average absorption: 150mA

- Environmental conditions: -20/80°C

- Display: mono-chromatic graphic LCD 320 x 240 pixel

- Keyboard: 6 charge-transfer buttons

- Sizes: 23.8 x 6.7 x 14.1 cm

- Weight: 1.4 Kg (cables and sensors excluded).