Tektronix WFM 601i, User Manual

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Measurement Theory
3–22
WFM 601i Serial Component Monitor
the green/magenta transitions). Figure 3-12 shows the graticule and the
measurement targets and timing delay scales.
B
R
G
C
M
YL
YL
B
R
M
C
G
Figure 3-12: Lightning graticule showing interchannel timing errors.
Luminance Gain – The vertical axis above and below the center box is the
luminance signal. The lower half is inverted. The luminance gain is correct when
the center dot (clamped black level) is centered in the target box and the end of
positive and negative excursions end at the top and bottom of the graticule.
Perfect monochrome signals appear as a thin vertical line. Any deviation or
bending off the center line indicates a color tinting away from the monochrome
setup of the display monitor. Luminance gain alone can be measured more
accurately in either the waveform or parade display modes of the monitor.
Interchannel Timing – The scale between the green and magenta targets is used
to check interchannel timing (CH-2 to CH-1 and CH-3 to CH-1) or signal delay.
If the color difference signal is not coincident with luminance, the transitions
between color dots will bend. The amount of this bending represents the relative
signal delay between luminance and the color difference signal. The upper half
of the display measures the P
B
-to-Y timing, while the bottom half measures the
P
R
-to-Y Timing. If the transition bends in toward black, the color difference
signal is delayed with respect to luminance and if it bends out toward white, the
color difference signal leading the luminance.
P
R
and P
B
Gain – The horizontal deflection of the top half of the display is an
indication of the P
B
gain and the lower half indicates the P
R
gain. If the color bar
signal dots are within the horizontal dimensions of the appropriate graticule
targets, the P
B
and P
R
gains are within 2% of the correct amplitude.