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A nine-pin serial connection port is located on the rear of the instrument. This
communication socket allows the instrument to be connected directly to a PC through the
standard RS232 serial port. The nine-pin connector cable may be oriented in one direction only.
The back panel also contains the vapor detector connector. A two wire connector can
be connected here and to the back of the solvent delivery unit to the pump stop or shut down
terminal. When the vapor sensor is activated by a leak, the detector will send out a contact
closure signal to the pump to shut off flow to the system.
The connector is polarity sensitive!
Pin #1 must connect to the pump stop and pin #2 must connect to pump ground.
DC POWER SUPPLY
The DC power supply is located toward the back of the detector. It provides
±15 volts
and ±5
volts
to the electronic components of the detector. The primary side of its transformer is
wired directly to the AC power module on the back panel.
DATA ACQUISITION
A separate data acquisition device is not necessary for either of the Model 302TDA. The
data acquisition device (DAD) has been integrated into each T model detector, available
through the serial interface located on the back panel.
The DAD system is more than a simple chromatography board, which only converts
analog voltage signals from GPC detectors into digital values for processing by a computer. It
is designed for unattended data acquisition, leaving the computer free to run other applications.
The DAD collects and stores analog data and controls linked accessories. On request, data can
be transferred to the host PC for further evaluation with the TriSEC GPC Windows Modules.
A.2 LIGHT SCATTERING DETECTOR
A.2.a
Theory
LIGHT SCATTERING THEORY
Light scattering is a well established technique for determining weight-average molecular
weights (MW) of polymers in solution. When light interacts with a molecule, it induces a
temporary dipole moment which oscillates in phase with the incident beam. In fact, the
molecule acts as an antenna and re-radiates light in all directions. This scattered light is
referred to as Rayleigh scattering and is of the same wavelength as the incident beam.
Due to thermal fluctuation, pure solvent also scatters light, although to a lesser degree
than the polymer solution. The information about the size and molecular weight of polymer is
experimentally derived from the excess light scattering intensity above the solvent background.
The excess light scattering intensity caused by the presence of polymer molecules in the
sample solution is directly proportional to polymer MW and sample concentration:
