Filter
Top Products
52 PI-SCX System Manual Version 2.E
52
This technique is also useful in high light level experiments, where the camera is again
photon shot-noise limited. Summing multiple pixels in software corresponds to collecting
more photons, and results in a better S/N ratio in the measurement.
Output Amplifier Selection
The output amplifier amplifies the collected charge from the output node and outputs it as
electrons/count. Although Figure 18 shows an array with a single output node and
amplifier, some PI-SCX systems are available with dual output nodes and amplifiers (one
set at each end of the shift register). If your system has dual output amplifiers, you can
choose the output amplifier to be used (High Capacity or Low Noise) via WinView/32 or
WinSpec/32 on the Acquisition|Experiment Setup…|Main tab:
High Capacity amplifier: Provides a spectrometric well capacity that is
approximately 3 times the well capacity for the Low Noise amplifier selection.
High Capacity is suitable when you have intense light signals or signals with
high dynamic range.
Low Noise amplifier: Provides the highest sensitivity performance and is
suitable when you have weak signals.
Note: The choice of output amplifier and analog gain setting should be considered
together for the best signal capture.
Analog Gain Control
Note: A gain control switch is located on the rear of the PI-SCX:1300 camera but has
been deactivated. However, analog gain is changeable via the WinView/WinSpec
software (on the Acquisition| Experiment Setup…|ADC tab card). If your camera
is not designed for analog gain selection, these settings will not be accessible in the
software.
Analog gain control (a function of the preamplifier) 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. In WinView/32 and WinSpec/32, the analog gain choices
vary depending on the CCD array and the number of output amplifiers:
Single Amplifier: Typically, three settings are available: Low 2x, Medium 1x,
and High 1/2x.
Dual Amplifier: Typically, three settings are available: Low 2x, Medium 1x, and
High 1/2x (Low-noise mode) or Low 4x, Medium 2x, and High 1x (High-
capacity mode).
The analog gain of the detector should generally be set so that the overall noise is ~1
count RMS. In most instances this will occur with the switch set to Medium. If the array
is a 1340 × 1300 configured with the low-noise output, Low will probably be a more
suitable Analog Gain setting. In situations where the A/D range exceeds that of the array,
it will generally be better to set the Analog Gain to High so that the signal can be spread
over as much of the A/D range as possible. This is a particularly important consideration
in absorbance measurements. Users who consistently measure low-level signals may
wish to select High, which reduces some sources of noise. Users who measure high-level
signals may wish to select Low to allow digitization of larger signals. Customized values
of gain can be provided. Contact Princeton Instruments for additional information.