System design to measure the large dynamic scope signal of shallow seismograph

The shallow seismograph is the main instruments of engineering geophysics. Its key technique lies in how to resolve the problem of the signal dynamic scope(requested 120 dB) because the signal is very weak. To solve the problem instrument designers used two kinds of essential techniques: one is instantaneous Floating amplification technology, another is 24bit A/Ds of Δ − Σ technique. However Floating amplification technology can cause signal no-line distortion and 24bit A/Ds of Δ − Σ technique acquisition rate is slow, so these technology can not resolve the problem of the signal dynamic scope efficiently. The advanced virtual instrument technologies have been introduced into the development of the seismograph in this design. We use virtual instrument technology to achieve instantaneous floating-point to enlarge the dynamic range of signals in the shallow seismic acquisition. Compared with the traditional Floating amplification based on high-performance processors, the hardware system of control and data acquisition completed by the data acquisition card and virtual instrument software — LabVIEW, does not require any external processor. The software can achieve a seamless connection, the system's structure and acquisition timing. So greatly simplified and enhanced the design of shallow seismograph.