Hologic DISCOVERY A, Technical Manual

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Discovery QDR Series Technical Manual
9-8
heights are magnified. The horizontal scale isn't affected and all detectors are displayed
regardless of the zoom value. Zoom Out will reverse what Zoom In has done.
9.1.3.4.5 Data Current Settings
This reports the Hi and Lo settings of the dark current for Bone, Tissue and Air.
9.1.3.4.6 Subtract Dark Current OFF/ON
The default for this button is OFF. Dark voltage is a residual reading for any equipment
that has current. Hologic allows 1 volt to compensate for dark current (see Figure 9-3).
Clicking on this button will remove the dark voltage from the Main Display bar graph.
The Field Engineer will not use Subtract Dark Current and it should always remain the
default.
9.1.3.5 Controls starting with Status Bits
Figure 9-8. Controls starting with
Status Bits
9.1.3.5.1 Status Bits
Detector values come back from the scanner as sixteen bit numbers, traveling through
some parts of the hardware on sixteen separate wires. The Status Bits field displays the
most recent value for each bit, and color-codes whether that bit has ever changed. Red bits
have not been changed, green bits have. The Reset button sets all the bits to red.
9.1.3.5.2 Reset
The Reset button re-starts the process of computing the means and standard deviations for
each filter-segment. It resets the number of samples to zero. It also resets the bits in the
Status Bits display.
9.1.3.5.3 Select Detector
This is an edit box that displays specific data about the selected detector. Select Detector
has a default of 108 (the middle of the bar graph as shown in Figure 9-3). This displays
both the currently selected detector (number) and allows a new detector to be selected by
insert a number in the edit box. A new detector can also be selected by dragging the
vertical blue line on the Main Display bar graph (see Figure 9-9). The number displayed in
the edit box will be automatically updated to reflect the line position.
AW-00335_001-0908