The Stanford Research Systems SR542 optical chopper with brushless DC motor offers frequencies from 0.4Hz to 20kHz, with low phase jitter, high resolution and accuracy, flexible synchronisation and computer control. The tried and trusted SR540 optical chopper is also available for 4Hz to 3.7kHz. Together we can cover all your optical chopping requirements — from simple measurements, to dual-beam and intermodulation experiments requiring the ultimate precision and accuracy.