Fractional Channel Display Scale Attribute
| Tag | (003A,0247) |
|---|---|
| Type | Conditionally Required (1C) |
| Keyword | FractionalChannelDisplayScale |
| Value Multiplicity | 1 |
| Value Representation | Single (FL) |
Fraction of the Presentation Group vertical display dimension assigned to the unit quantity (least significant bit) of the Channel samples (see Section C.10.9.1.10). Required if Absolute Channel Display Scale (003A,0248) is not present, may be present otherwise.
Section C.10.9.1.10
C.10.9.1.10 Channel Display Scale
Fractional Channel Display Scale (003A,0247) or Absolute Channel Display Scale (003A,0248) specifies the vertical scaling of the channel display. If both Attributes are provided, the selection of which to use for display control is implementation dependent.
Fractional Channel Display Scale (003A,0247) specifies the fraction of the Presentation Group vertical display dimension used to offset each unit of the waveform sample value from the baseline Channel Position (003A,0245). Positive offset values are towards the top of the display area.
Note
E.g., for a channel whose Fractional Channel Display Scale (003A,0247) value is 0.004, and whose Channel Position (003A,0245) value is 0.5, a sample whose value is -37 would be displayed at a position
0.5 - (-37 * 0.004) = 0.648
of the total vertical display dimension below the top of the Presentation Group display area.
Absolute Channel Display Scale (003A,0248) specifies the nominal physical distance on a display device (monitor) used to offset each unit of the waveform sample value from the baseline Channel Position (003A,0245). The display application needs to know the vertical pixel scaling of the display device to effectively apply this Attribute. The Channel Sensitivity (003A,0210) value in Channel Sensitivity Units (003A,0211), divided by Absolute Channel Display Scale (003A,0248) value, gives the real-world scaling of the intended display.
Note
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This Attribute is useful for size consistency between softcopy display and classical hardcopy waveform printed charts. E.g., a channel whose Channel Sensitivity (003A,0210) value is 44 uV (per least significant bit), and whose Absolute Channel Display Scale (003A,0248) value is 0.44 mm, has a real-world display scale of 0.1 mV/mm.
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E.g., for a channel whose Absolute Channel Display Scale (003A,0248) value is 0.44 mm, and that is being displayed on a monitor at 4.1 pixels/mm, a sample whose value is 107 would be displayed at a position
107 * 0.44 * 4 = 193.028
pixels above the Channel Position (003A,0245) baseline.
Display for waveform samples that would lie outside the Presentation Group display area is unspecified.
Negative values of Fractional Channel Display Scale (003A,0247) and Absolute Channel Display Scale (003A,0248) are allowed.