Application of Impact Imaging Method on Nondestructive Detection of Void Defects in Sandwich-Structured Immersed Tunnel

Table 2

Parameters of the geode 24-channel seismograph instrument.

Configuration	Technical details
Main acquisition station	Single station 24 channels, 24 bit
Dynamic range	144 dB (system), 110 dB (instantaneous, measured) at 2 ms, 24 dB
Bandwidth	1.75–20 kHz
Common mode rejection	>100 dB (<100 Hz, 36 dB)
Noise floor	0.20 μV, RFI at 2 ms, 36 dB, 1.75 to 208 Hz
Stacking trigger accuracy	1/32 of sample interval
Maximum input signal	2.8 V PP, 0 dB, 177 mV PP, 24 dB,
Input impedance	20 kOhm, 0.02 μf
Preamplifier gains	Optional configurations include 12 and 24 dB or 24 and 36 dB
Sample interval	0.02, 0.03125, 0.0625, 0.125, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, 16.0 ms