MEASUREMENTS

Chrominance-to-Luminance Gain & Delay Inequalities
VM700A Automatic Measurement
Chrominance-to-luminance gain and delay errors can be
measured by selecting ChromLum GainDelay in the VM700A
MEASURE mode. Numeric results are given in this mode, and
both parameters are simultaneously plotted on the graph. As
shown in Figure 27, delay is plotted on the X axis and gain
inequality is plotted on the Y axis. These measurements are
also available in the VM700A AUTO mode.
Calibrated Delay Fixture
Another method of measuring these distortions involves use of
a calibrated delay fixture. The fixture allows you to incrementally
adjust the delay until there is only one peak in the baseline,
indicating that all delay errors have been nulled out. The delay
value can then be read from the fixture, and gain measured
from the graticule. This method can be highly accurate, but
requires the use of specialised equipment.
• NOTES
9. Harmonic Distortion
If harmonic distortion is present, there may be multiple aberrations
in the baseline rather than one or two clearly distinguishable
peaks. In this case, nomograph measurement techniques are
indeterminate. The VM700A, however, is capable of removing
the effects of harmonic distortion and will yield valid results in
this case. Minor discrepancies between the results of the two
methods may be attributable to the presence of small amounts
of harmonic distortion, as well as to the higher inherent resolution
of the VM700A method.
Figure 27. The ChromLum GainDelay
VM700A MEASURE mode.
display in the
29