Powerful Integral Control Rapid operation with ease of use is provided by the powerful software built into the computing system of the Aquarius instruments. The standard software is remarkably comprehensive but may be expanded, at any time, by E-SEF to release additional software modules when required. Double Beam Optical System The fully symmetrical double beam system of the Aquarius instruments provides for the highest accuracy of measurement coupled with a very high level of stability with time. Both sample and reference beams are provided with the same sampling space and facilities, thus catering for the widest possible range of experimental requirements and not limited to just a single cell in the reference beam.