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The SR200 Series Boxcar Averager System is a modular instrumentation
platform designed to acquire and analyze fast analog signals.
The system consists of a NIM compatible mainframe and modules
which can be selected to tailor a system to individual requirements.
The SR200 series is flexible enough to handle gate widths from
100 ps to 150 µs, repetition rates up to 50 kHz, and has
both analog and digital outputs. With its low-noise inputs and
low-drift outputs, the SR200 series is the standard for gated
integrators and boxcar averagers.
Gated Integration
Gated integrators and boxcar averagers are designed to recover
fast, repetitive, analog signals. In a typical application, a
time "gate" of predetermined width is precisely positioned
relative to an internal or external trigger to coincide with your
signal. A gated integrator amplifies and integrates the signal
that is present during the time the gate is open, ignoring noise
and interference that may be present at other times.
Boxcar Averaging
Boxcar Averaging refers to the practice of averaging the output
of the gated integrator over many shots of the experiment. Since
any signal present during the gate will add linearly, while noise
will add in a "random walk" fashion as the square root
of the number of shots, averaging N shots will improve the signal-to-noise
ratio by a factor of √N.
Analog and Digital Measurements
The SR200 series is designed to work without a computer, allowing
you to quickly "tune-up" your experiment, or with a
computer, automating complex measurement sequences. Modules like
the SR235 Analog Processor perform signal processing functions
(e.g., ratioing and background subtraction) without the need for
a computer, while the SR245 Computer Interface gives you complete
access to boxcar measurements over GPIB or RS-232.
SR200 Series NIM Modules
The SR200 series modules are briefly described below. Further
details, including specifications and features can be found in
the following pages on this website.
SR280 NIM Mainframe and
Display Module
The SR280 Mainframe and Display module is a rack-mountable NIM
bin which can house up to nine single-width NIM modules. The three
right-most slots in the bin are occupied by a NIM-compatible power
supply and display which provides ±12 V and ±24
V to the other NIM modules. The display module also contains an
analog meter, digital meter, and bar graph meter which are useful
for monitoring the output of the boxcar system.
SR250 Gated Integrator Module
The SR250 Gated Integrator module is the basic building block
of the SR200 series. The SR250 is a complete, single-channel gated
integrator and boxcar averager with gate widths from 2 ns to 15
µs. You can average from 1 to 10,000 samples, and the "last
sample" feature lets you bypass averaging and access the
gated integrator output directly.
SR255 Fast Sampler Module
The SR255 Fast Sampler allows you to do gated integration with
gate widths as short as 100 ps. Four discrete gate widths are
provided: 100 ps, 200 ps, 500 ps, and 1000 ps. Output is provided
in both analog and digital form.
SR245 Computer Interface
Module
The SR245 adds both analog and digital data acquisition capabilities
to the SR200 series. Eight analog I/O channels can be configured
as inputs or outputs, and two front-panel digital I/O ports are
provided. The SR245 can communicate with a computer over the RS-232
and GPIB interfaces.
SR240A Quad 350 MHz Preamplifier
Module
The SR240 contains four DC to 300 MHz amplifier channels, each
with a gain of 5. The SR240 is ideal for amplifying low-level
signals from photomultipliers and photodiodes before being measured
by the SR250.
SR200 Gate Scanner Module
The SR200 Gate Scanner is designed to automate waveform recovery
by providing the voltages needed to scan the SR250's gate delay.
Scan times from 10 ms to 5 minutes can be selected.
SR235 Analog Processor Module
The SR235 Analog Processor performs a variety of functions without
the need for a computer. Its two inputs can be combined to form
an "argument", A, B, A-B, AB/10, 10A/B, or √(A2+B2).
The SR235 then outputs a function F(x) of this argument corresponding
to x, x2, ln(x), dx/dt, or (dx/dt)/100.
SR272 Data Acquisition Software
The SR272 is a Windows compatible software package designed to
acquire, display and analyze data taken with the Boxcar system.
The program works with the SR245 Computer Interface module over
the GPIB or RS-232 interface. Features include on-screen cursors,
auto-scaling, smoothing, and curve fitting.
SR275 Display Module
The SR275 Display Module is provided for users who already own
a NIM bin and power supply. It contains the same three meters
as the SR280, but has no
power supply.
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