Semi-automated capacitance measurements for investigating the dielectric and elastic properties of liquid crystals

Describes a versatile semi-automated system to determine the elastic and low-frequency dielectric behaviour of liquid crystals using the capacitance-voltage or capacitance-frequence responses of aligned samples. The results are used to evaluate elastic moduli k 11 and k 33 and macroscopic characteristic relaxation times for reorientation at different temperatures for a number of materials. Capacitance-frequency measurements can be made in the 100 Hz to 50 kHz region to an accuracy of +or-1% and a precision of +or-0.05% and capacitance-voltage measurements can be made from 0 to 500 V AC at 1 kHz and 0 to 50 V AC at 20 kHz to an accuracy of +or-2% and a precision of +or-0.2%, giving the elastic moduli k 11 and k 33 to an accuracy of 5% and 10% respectively.