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These high stability variable frequency optical choppers each include a set of chemically blackened photoetched chopping discs. The mini chopper is an excellent choice for applications requiring a compact package. Set-ups needing more than one chopper frequency signal should consider the dual frequency chopper version. The chopping discs come in a variety of slot apertures and allow operation. Beam diameter is limited to 0.75mm when using the 200-slot disc and 1.0mm when using the 40 slot mini disc. The easy-to-interchange blades are made of non-magnetic, half hard brass and can be used in combination. Chopping frequency is set by adjusting a ten-turn dial or by applying an external DC voltage to the BNC input. Reference output is a TTL pulse and is in-phase with chopping action. The 5 digit led display gives a direct read-out of the chopping frequency. Power: 90-130V or 180-260V; 50/60Hz; 12VA max. Power supply included. Choppers are often used together with lock-in amplifiers.
Individual replacement blades are available in multiple slot variants. Both the single and dual frequency choppers can utilize the same blades. Single frequency models, however, will not utilize the internal slots on the dual frequency blades. These blades have a 1:1 mark: space-duty-cycle ratio. Ratios with greater periods of non-transmittance can be obtained by mounting two disks of the same type at the same time, with slight differences in alignment.