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Earthquake Engineering Research - HKU Libraries - The University ...

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591<br />

Time series Acceleration, Velocity, Reference Velocity<br />

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Noise signal recorded at ground level<br />

Figure 2. 1, 2 Detailed time series to underline the resolution of the signal.<br />

<strong>The</strong> conclusion of this test is that a 16-bit A/D resolution with gain 1 00 and full-scale set to +/-0.1V is<br />

suitable for ambient vibration measurements. If the gain is set to 2, which correspond to +/-5V fullscale,<br />

then the system is suitable for strong motion type measurements. <strong>The</strong> difference between this<br />

settings and the use of a 2 1 -bit or greater resolution A/D is the overall dynamic range. In other words,<br />

the 16-bit system requires different settings for different type of measurements while the 21 -bit or<br />

greater system covers both applications with one setting. Of course the difference in price is<br />

significant and can become a cost/benefit factor.<br />

2.2 Number of Channels<br />

Detailed structural monitoring requires a high number of channels. <strong>The</strong> last two systems (See Table<br />

1.1) have standard 64 channels and optional 128

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