User Manual - TRS-RenTelco

Option VGA Detailed Measurement Information
Ch-Ch Mismatch Measurement
The Ch-Ch Mismatch measurement measures the difference in any steady-state
voltage amplitude between R, G, and B video outputs. The amplitude difference
of all the 32 steps is measured between two channels. The maximum amplitude
difference is shown as the result.
Signal Source
The test signal used for Ch-Ch Mismatch measurement is a 32 Step Staircase
(required to test for compliance with the VESA Test procedure), which is located
on the Test Signal Files CD-ROM.
The 32 Step Staircase test signal contains a pattern where each step is equal to
1/32 of the maximum input voltage (700 mV) for R, G, and B channels. The PC
color setting must be set to True Color mode.
If you plan to take only Ch-Ch Mismatch measurement, use a 32-Step Staircase
Full Field test pattern. Select the bitmap file that matches the format and the
refresh rate of the test. For example, look for the 640x480 -32Steps.bmp file to
test a 640x480 resolution format.
You can also use a Matrix signal as a test signal. For more information on the
Matrix signal refer to page 2 -16. For example, look for the 640x480 -Matrix.bmp.
This file has a 32 Step Staircase which is suited to the Ch-Ch
Mismatch measurement.
Interpreting Results
The maximum limit for the Ch-Ch Mismatch is 6% of any voltage over the full
range in accordance with the VESA specifications.
The ideal value of Ch-Ch mismatch result should be 0 mV. A positive value
indicates that the step voltage of the first channel is greater than that of the
second channel. A negative value indicates that the step voltage of the first
channel is less than that of the second channel.
For example, -8.923 mV mismatch between G to B channel indicates that the
step voltage of the G channel is less than the step voltage of the B channel.
How Results are
Calculated
For a given step, the voltage amplitude is measured with reference to the back
porch. The amplitude is measured for two channels (say G and B). The
amplitude difference of two channels is calculated and displayed as the result.
The results are reported as a percentage by dividing the calculated result by
Vmax steady state (typically 700 mV).
3-40 VM5000 Automatic Video Measurement Set User Manual