Data Translation DT3152-LS, Руководство пользователя

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Chapter 2
16
Note that since the image has been shifted up by 0.4032 V, a voltage
level of
−
0.4032 V, relative to the camera's output, is now digitized as
black.
Step 2. Apply the Gain
With an offset of 0.4032 V, the maximum point on the signal is now
1.5032 V. However, the ADC on the DT3152-LS board can digitize
voltages between 0.0 V and 1.28 V only. To digitize the part of the
signal between 1.28 V and 1.5032 V, you must decrease the amplitude
of the video signal. Referring to
Table 1 on page 13 , since
V
max
+ offset = 1.5032 V, which is greater than 1.28 V, use a gain of 0.5.
Figure 5 shows the effect of gain on the video signal.
Figure 5: Use of Gain to Adjust the Amplitude of the Signal
−
0.5 V
0 V
0.5 V
1.0 V
1.5 V
2.0 V
Signal with offset = 0.4032 V;
gain = 1
Signal with offset = 0.4032 V;
gain = 0.5