Teledyne 440, Системное руководство, Страница: 123 / 256

6 – Operating Procedure
DPN 402196 Issue 4.1 © Teledyne TSS 6- 19
Oscilloscope Display
Although not part of the Run Display screen, you may select the oscilloscope from within this screen by
selecting ‘Scope and Spectrum Analyser Window’ from the View option. Correct interpretation of the
oscilloscope can assist in the understanding and operation of the System.
The oscilloscope display includes three ‘panels’. These panels represent the signals on starboard,
centre and port coils. The oscilloscope displays the coil signals as green traces. It updates the traces
using average values taken over eight consecutive sample cycles. This process removes most noise,
although any significant noise levels will remain visible. Provided the noise does not encroach on either
of the sample regions, as shown in example (h) of the fold-out drawing, the measurement process
should not be affected. You should investigate and remove any severe causes of noise pick-up.
For each of the oscilloscope panels, the left-hand edge corresponds to a time immediately after the
end of the voltage drive pulse and pre-sample period (see
Appendix A "Operating Theory" for a full
description of the measurement cycle timing). The width of each panel represents a timebase period of
either 1200µs or 600µs from the start of the trace, as indicated by scale gradations on the x-axis of
each panel.
There are three critical regions on the oscilloscope display, with their boundaries marked by vertical
broken white lines. Example (a) in the fold-out drawing shows these:
❐ The first, called the ‘Early region’, lies between 130µs and 230µs on the timebase scale. Dur-
ing this period, the System makes 25 measurements of the signal and calculates an average
value for these.
❐ The second, called the ‘Standard region’, lies between 300µs and 400µs on the timebase
scale. During this period, the System makes 25 measurements of the signal and calculates an
average value for these.
❐ The second, called the ‘Zero region’, lies between 1000µs and 1100µs on the timebase scale.
The System averages the 25 measurements that it makes during this period and uses the
result as the zero reference against which the System compares the measurement made dur-
ing the both the ‘Standard region’ and ‘Early region’ periods.
The two differences between these three averages is the derived signal strength is used to determine
the target voltages for the channels on the Run Display screen.
The y-axis has gradations from zero to 100%, with the absolute signal voltage represented by 100% on
this axis appearing at the bottom centre of the oscilloscope screen. Saturation occurs when the signal
voltage exceeds 100% on this scale. Provided the saturation does not extend into the ‘Sample region’,
the measurement will not be affected. The fold-out drawing shows examples of slight saturation (f) and
full saturation (g).
6.3.7 Data Logging
To provide the post-processing engineers with a detailed account of the survey it is important to
maintain a full log of events as they occur during a survey.
The survey log should therefore include:
❐
The data logged to an external logger
❐
The video recording of the 440 System installation and configuration procedures (if one has
been made)
❐
The video recordings from cameras on board the ROV