Teledyne Princeton Instruments PI-MAX 3, System Manual

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86 PI-MAX
®
3 System Manual Issue 2
7.10 Controller Gain {Analog Gain}
Controller gain, which is a function of the preamplifier, is software-selectable and is
used to change the relationship between the number of electrons acquired on the CCD
and the Analog-to-Digital Units (ADUs or counts) generated.
Three factors should be considered when configuring Controller Gain:
• The intensity of the incoming signal;
• Binning;
• CCD saturation.
Selecting the amount of gain is done on the Acquisition
►
Experiment Setup…
►
ADC
tab {Analog to Digital Conversion expander}. The choices are:
• 1 {Low};
Users who measure high-level signals may wish to select 1{Low} for digitization
of larger signals: more electrons are required per ADU.
Since binning combines the signal from two or more pixels, the user may also
want to select 1 {Low} if binning is being applied.
In both instances, the goal is to prevent CCD saturation and maximize signal
acquisition.
• 2 {High}.
Users who consistently measure low-level signals may wish to select 2 {High},
which requires fewer electrons to generate an ADU and reduces some sources
of noise. If saturation occurs at this setting, 1 {Low} should be selected.
7.11 Digitization
During readout, an analog signal representing the charge of each pixel (or binned group
of pixels) is digitized. The number of bits per pixel is 16.
Some PI-MAX3 cameras have two complete analog channels including separate A/D
converters. Because the readout noise of CCD arrays increases with the readout rate, it
is sometimes necessary to trade off readout speed for high dynamic range. The two
analog converters, both high speed, are optimized for slower read rates by digitally
processing the signal in the camera before transferring it to the host