SC(1-15)-DAC is a highly configurable data acquisition software package which communicates with the BCE seismic signal conditioning board and a notebook based PCMCIA A/D card. The downhole sesimic testing (DST) systems can be expanded up to 15 channels (30 channels if two A/D board are used), but typically uniaxial (SC1-DAC), biaxial (SC2-DAC), triaxial (SC3-DAC), and true interval six channel systems (SC6-DAC) are assembled.

Typical Configurations Parameters are outlined as follows:

Data Gain
    0 to 84dB in 6 dB increments.
Sample Rate - KHz

Depends upon channels used. A maximum sample rate of 330 KHz is available. For SC1-DAC two channels are required (ie., trigger and seismic data channel); therefore, the maximum sample rate available for each channel is 165 KHz. For SC3-DAC, the maximum sample rate per channels is 82 KHZ.

Sample Time - ms
    Total amount of data to capture.
Sensor Sensitivity

Either accelerometers or geophones can be used as seismic sensors. The sensitivity parameter is provided by the manufacturer. All data in SC(1-15)-DAC is stored in real units (eg., m/s or m/s2) so that the sensitivity parameter is required to convert measured voltages to real units.

Anti-Aliasing Filter Order Specification  - 2nd or 4th Order
    Typically set to 2nd Order.
Trigger Parameter - 0-10mV, 0-1000mV, 0-3.5V, and Contact

General the trigger is specified as a Contact (eg., hammer strikes truck pads). But transducers can also be used as triggering devices. Possible trigger transducer are accelerometers (0-10mV and 0-1000mV measurement ranges) and geophones (0-3.5V measurement range).

Trigger Level - 0 to 100%

Trigger level which signifies an event. This level percentage is based upon the range previously specified in Trigger Parameter.

PreTrigger - 0 to 30%

Specifies how much data should be captured prior to the trigger. This level percentage is based upon the Sample Time specified. For example, a PreTrigger  set at 10% for a total sample time of 10 ms will give 1 ms of pretrigger information. The preTrigger allows the investigator to assess ambient noise.

Source Parameters

Specify the Radial Offset of the source from the seismic cone (SC) and the Depth Offset from the ground surface in meters. The Probe Depth parameter identifies the current SC depth in meters.

Data File Specification

The parameters set here allow the investigator to automatically name stored data files based upon data and time stamps, probe depth, type of source, polarization of source wavelet, and default directory specified.

Note: The digital trigger channel process data at the maximum rate of 3us so that highly accurate and repeatable triggers are obtained.

SC1-DAC

The data acqusition screen for SC1-DAC is illustrated below. The Stack button allows the investigator to carry out data stacking.

The figure below illustrates a typical SC1-DAC source file with trigger channel displayed. The light blue line signifies the pretrigger level.

SC3-DAC

The data acqusition screen for SC3-DAC is illustrated below. In this case the investigator specifies X, Y,and Z sensor sensitivities.

The figure below illustrates a typical captured  SC3-DAC source file with the X, Y, and Z time series illustrated.

SC6-DAC

The data acqusition screen for SC6-DAC is illustrated below. In this case the investigator specifies X, Y,and Z sensor sensitivities for the two true interval probes.

A typical SC6-DAC data capture screen is illustrated below. The user can change the relative sizes of the seismic data chart and the trigger chart by moving the red chart splitter  bar illustrated.

The figure below illustrates the above figure with the seismic data plotted with respect to each time series Min / Max Values. This option was enabled by selecting check box Set MinMax.