418M Optical Chopper
The 418M optical chopper consists of a modular control unit suitable for fitting in the 417 housing, and is coupled by a 2m long lead to the chopping head. Four easily-interchangeable chopping discs are provided as standard which allow chopping frequencies in the range of 5 Hz to 3kHz.
A variable aperture 2-slot disc and higher frequency discs are also available. The chopping frequency is indicated by a digital indicating dial and a squarewave reference output suitable for use with lock-in amplifiers is provided.