In a recent paper, we reported a low-cost, high-resolution polarimeter based on a principle originally proposed by in which the rotation angle is determined by measuring the phase difference between two harmonically modulated polarised laser beams -an 'object beam' that passes through the sample under test and a 'reference beam' that bypasses the sample. Importantly, the method required no precision-engineered optomechanical parts, relying instead on a timing-based procedure to determine the optical rotation angle. The specific optical set-up we used (Fig. ) was based on an optimised layout proposed by Vishnyakov et al., with a variety of design simplifications and cost-saving component substitutions. By eliminating all expensive components, we were able to bring the total build-cost of the polarimeter down to around $1000, while maintaining an accuracy that matched the performance of far costlier commercial instruments.