SCT-300CD Rotating Optical Chopper

Description

Features

SCT-300CD is a high stability variable frequency optical chopper. The basic system consists of a control unit, a chopping head and set of four chemically blacked photo etched discs. This system provides operation over the frequency range 5 Hz to 3 kHz. A wide selection of additional discs and accessories is available to extend the frequency range and to satisfy individual requirements.

• 5 Hz – 3 kHz standard optical chopping frequency range (0.015 Hz to 40 kHz options are available)
• 102 mm diameter discs
• Choice of control units
• Compact optical chopper head
• Low noise and vibration
• Photochemically etched non-magnetic discs
• Variable aperture
• Range of accessories

The SCT-300CD control unit has a 5-digit display of the chopping frequency. Chopping frequency can be controlled externally by applying an analogue voltage to a „Control“ BNC. A „Reference“ BNC provides a TTL level output, generated directly from the opto-switch on the chopping head. This signal has constant phase relative to the chopping action and can be used as the reference for other instruments such as lock-in amplifiers.

The SCT-300H optical chopper chopping head supplied with the standard system may be bench bolted or provided to enable parts, such as a high frequency accessory or blade protector, to  be attached. For lower frequency operation, the chopper head can be fitted with a reduction gearbox motor.

The set of four chopping discs included with the system (part number SCT-300D) provides a choice of 2, 5, 10 and 30 slots, each having 1:1 mark to space ratio. Variable apertures can be achieved by mounting two identical discs simultaneously. Additional discs, with up to 445 slots, are available to extend the chopping frequency up to 40 kHz. Although the standard discs are chemically blacked other finishes, such as gold plating, are available.

Specifications

SCT-300CD Control Unit

• Output Voltage: 15 V DC Maximum
• Stability: ± 0.01 %/°C
• Frequency Control: Internal – Manual Control via 10 turn potentiometer. External – BNC connector for 0 to 15 V
• Frequency Read Out: 5 digit 14 mm LED display with 0.01 Hz resolution, 0.1 Hz or 1 Hz resolution depending on frequency
• Frequency Stability: Short term – see phase jitter. Long term - ± 0.1 % of maximum frequency
• Reference output: 5 V HCT TTL signal via BNC socket
• Power Requirement: 100 – 130 V or 200 – 260 V AC, 50 or 60 Hz, 12 VA
• Dimensions: 254 (W) x 76 (H) x 178 (D) mm
• Weight:6 kg

SCT-300H Chopping Head

• Motor: 11 pole DC motor, sleeve bearings with more than 6000 hours lifetime, 0 – 6000 rpm reversible
• Reference pick-up: IR led and phototransistor pair with Schmitt trigger
• Dimensions: 73 (H) x 75 (L) x 32 (W) mm, without disc.
• Mounting: Optical stalk – adjustable between 6.5 and 14.0 mm diameter. Mounting holes – 2 x 3 mm

SCT-300D Set of Chopping Discs

• Disc types: 2, 5, 10 and 30 slot
• Material: Half har brass, 0.5 mm thick
• Diameter: 102 mm
• Surface Finish: Chemically blacked
• Mark to Space Ratio: 1 to 1 with ohne blade