Waters 2475, Operator'S Manual, Page: 27 / 228

Principles of operation 1-13
The following figure shows the relationship between increased time-constant
and response times.
Effect of filter time constant
Electronics
The electronics consist of the following components:
• Preamplifier board – Collects and processes the analog input signals
from the PMT and photodiode to the microprocessor for further signal
conditioning. Sample and reference signals are integrated and A/D
conversion is performed simultaneously. This component ensures the
best rejection of common mode noise in the two beams, leading to a quiet
baseline.
• Personality board – Receives inputs from the preamplifier board and
external events. It also provides control of the optics positioning
subsystems and the lamp power supply.
• CPU board – Contains the digital signal processor, communication
ports, nonvolatile (battery backed-up) RAM and flashable RAM space in
which the firmware resides.
• Ethernet communications interface – Enables the detector to
communicate with data system software.
TP02824
0
0.5 1
-10
10
30
50
70
90
110
1.5
Time (minutes)
Re
sponse
0 sec.
1 sec.
2 sec.