Gain Settings In More Detail - Basler A101f User Manual

Operation and Features

3.6.1 Gain settings in more detail

The output signals from the pixels in the CCD sensor normally range from 0 Volts when the pixels
are exposed to no light to 0.4 Volts when they are exposed to bright light. Within that range, the
sensor characteristics are linear. Saturation starts at 0.4 Volts. Further exposure results in a
higher sensor output signal but linearity is no longer guaranteed.
The default factory gain is set for an amplification factor of 5.0 (14 dB). At this setting, the sensor's
normal linear output range of 0 V - 0.4 V is amplified to 0 V - 2.0 V. The peak-to-peak input range
of the ADC is 0 V - 2.0 V. Thus when the gain is at factory default, the amplified output of the
sensor maps directly to the input voltage range of the ADC.
Gain is adjustable and can be programmed on a decimal scale that ranges from 0 to 511 (0x000
to 0x1FF). However, only the settings from 0 to 319 (0x000 to 0x13F) are effective. Settings
greater than 319 will not increase the gain and should not be used. The settings result in the
following amplification:
• 0 = 4.5 dB
• 319 = 34.5 dB
• In between, the change in dB setting is linear.
• The gain can be adjusted in steps of 0.094 dB.
The desired 14 dB default gain is achieved when the gain is programmed to 101 (0x065). You
should find that the default gain setting on your camera is near to this value.
Reducing the gain below 101 results in mapping more than the linear operating range of the
sensor to the ADC. Increasing the gain to more than 101 maps a smaller portion of the sensor's
linear output signal to the ADC.
If you know the decimal number setting for the gain on your camera, the equivalent decibel value
can be calculated as follows:
3-12
DRAFT
34.5 – 4.5

×
------------------------- -
dB = DN

319

+ 4.5

f
BASLER A101