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Digital Automatic Polarimeter
The POLAR-LµP Digital Polarimeter is a versatile,
easy-to-use instrument. Microcomputer controlled, and with no
moving mechanical parts, it is based on the Faraday Modulation
and Compensation technique.
The POLAR-LµP automatically measures and displays optical and
specific rotation, sugar scale and the concentration of optically
active compounds. Optional real time clock (RTC) and sample
counter is available for GLP protocols.
All instrument controls are made by using the 4 key panel or via
serial interface (RS 232).
The optical unit, designed as an optical bench, is separated
from the electronic display unit to provide short warm up time,
maximum stability and low noise especially when measuring dark samples.
A wide range of stainless steel or quartz sample tubes
for single probe or flow through operations.
The POLAR-LµP uses the Faraday Effect to compensate the
rotation angle caused by the optically active sample:
alfasample= alfacomp= V*d*Icomp*N
Thus, the compensation current Icomp is proportional to alfasample.
The determination of the rotation angle of the sample is therefore
a simple current measurement and does not necessitate any
mechanical moving parts.
After corresponding calibration, the measured rotation angle is
indicated in millidegrees (m°).
In addition, a Faraday Modulation takes place in the same coil
in order to obtain a definite balancing criterion independent to
the light source intensity or the absorbtion of the sample.
The application of an alternating current (AC) with frequency f1
produces a modulation of the polarized light with twice of this frequency.
If an optically active sample is present, its oscillation is superposed by
the frequency f1 and fed to an integrator which is phase-sensitive to f1.
This integrator modifies the compensation current Icomp
taking into account the correct sign of rotation,
until the oscillation component f1 becomes zero,
i.e. until the device is in balanced condition.
This process is extraordinary fast which means that Icomp is proportional,
in real time, to the amount of the optically active sample in the cell.
Icomp is then transformed via microprocessor to a calibrated readout
for the serial and analog interface.