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Reference
3-30
WFM700 Series Waveform Monitors User Manual
Listed below are general guidelines for setting gamut alarm limits for the
Diamond and Arrowhead displays.
Default Thresholds. Use the Grat / Gamut Default Setup submenu of the
Configure menu to select the standard used for default gamut thresholds: Tek or
IBU-R103. The Tek thresholds are the default gamut thresholds historically used
by video monitoring equipment made by Tektronix, Inc. and are not intended to
conform to an officially accepted video standard.
NOTE. When you select the Tektronix default limits, the RGB, Luma, and Y+C
gamut thresholds are reset to the default values defined by Tektronix. When you
select the EBU-R103 default limits, only the RGB and Luma gamut thresholds
are reset since the Y+C gamut limits are not defined by the EBU-R103 standard.
When you touch the Default soft key in any of the Gamut Limit menus, all of the
gamut limit thresholds are reset to the standard indicated on the soft key.
Diamond Display Gamut Limits. Use the Gamut menu to set the upper and lower
RGB thresholds for a 5 mV tolerance ( +705 mV and --5 mV). This will cover
the tolerance of any signal generator that provides color bars. This tolerance is
close enough to the nominal values of 700 mV and 0 mV to be undetectable by
the human eye.
Set the Horizontal/Horiz+Vert soft key setting to Horiz+Vert. This setting will
trigger on gamut errors that form a block covering several video lines, and thus
are more visible to the human eye.
Arrowhead Display Gamut Limits. Use the Limit Format soft key to set the
instrument for NTSC or PAL gamut measurements. For North American
applications of NTSC video signals, set the Setup control to 7.5%. In addition,
set the upper Y+C Composite threshold to 120 IRE because that is the level at
which a TV transmitter starts to clip the signal. Set the lower Y+C Composite
threshold to --24 IRE because that is the lower limit of chrominance excursions.
For the majority of PAL video signal applications, set the Setup control to 0%.
Set the upper Y+C Composite threshold to 935 mV and the lower Y+C
Composite threshold to --235 mV because those are the limits of chrominance
excursion.
For both NTSC and PAL signals, set the Horizontal/Horiz+Vert soft key setting
to Horiz+Vert. This setting will trigger on gamut errors that form a block
covering several video lines, and thus are more visible to the human eye.
Set the upper and lower luminance thresholds for a 3% tolerance (103% and
--3%) to monitor excessive luminance excursions.
Setting Gamut Alarm
Limits