C.10.9.1.8 Waveform Data Display Scale

Waveform Data Display Scale (003A,0230) specifies the recommended display scale in the time dimension for the waveform data in units of mm/s. The display application needs to know the horizontal pixel scaling of the display device to effectively apply this attribute. The Waveform Data Display Scale (003A,0230), divided by the Sampling Frequency (003A,001A), times the display scaling in pixels/mm gives the number of horizontal pixels between subsequent samples.

Notes: 1. This presumes a conventional waveform display with time in the horizontal dimension, and waveform measured quantity in the vertical dimension.

2. This attribute is useful for size consistency between softcopy display and classical hardcopy ECG printouts. E.g., for the channels of a multiplex group whose Sampling Frequency is 400 Hz, and whose Waveform Data Display Scale (003A,0230) is 25 mm/s, and which is being displayed on a monitor at 4.1 pixels/mm, the horizontal interval between samples is

25 / 400 * 4.1 = 0.25625 pixels

How the display application renders samples at fractional pixel spacing is implementation dependent.

C.10.9.1.9 Channel Position

Channel Position (003A,0245) specifies the position of the channel display baseline in the Presentation Group vertical display dimension. The channel position is relative to the top of the display area. Each Presentation Group display area is defined with vertical dimension positions of 0.0 (top of display area) to 1.0 (bottom of display area).

Notes: 1. This presumes a conventional waveform display with time in the horizontal dimension, and waveform measured quantity in the vertical dimension.

2. Compare Bounding Box Annotation Units (0070,0003) value DISPLAY in Section C.10.5 Graphic Annotation Module.

Channel sample value 0 maps to the Channel Position (003A,0245) display baseline. The real world value associated with the baseline is specified in Channel Baseline (003A,0213).

Multiple channels may overlap, and may share the same Channel Position (003A,0245).

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.

Notes: 1. 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.

2. E.g., for a channel whose Absolute Channel Display Scale (003A,0248) value is 0.44 mm, and which 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.