Overview
The model 651-1 uses the standard head. This is a dual port design allowing two optical beams to be modulated simultaneously at different frequencies, f1 and f2. Two reference (sync) outputs are made available at the control unit, corresponding to f1 and f2, for use with signal recovery processing electronics, such as a lock-in amplifier.
Two small blanking plates are provided with the standard head and one of these allows either the top port or the bottom port to be blanked off to reduce the effect of any stray light passing through the unused path. The second plate provides some measure of beam restriction when using large diameter beams on the higher frequency (and therfore smaller aperture) port. The standard head is supplied complete with a flat base plate to allow it to be used in a free standing mode on a bench type surface. A special feature of this support allows the head to be used in the horizontal plane for modulating vertical beams. The base plate can be removed and standard optical mounting posts employed instead if preferred.
- Remote chopper heads
- Quartz crystal frequency accuracy and stability
- Internal or external frequency reference
- Sync outputs
- Choice of 3 models
- Fully enclosed housings for safety and low noise
- Optical absorption, reflection and transmission measurements
- Dual-beam ratiometric measurements
- Automatic background subtraction in boxcar averager experiments
The 650 series of light choppers features a control box with separate chopping heads for remote operation.
Specifications
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General |
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Dual-aperture remote head chopper with internal or external reference frequency. Two sync outputs. |
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Frequency outer sector inter sector |
10 Hz to 3200 Hz 100 HZ to 3200 Hz |
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Control external |
Application of 0.5 V to 10 V pk-pk sine or squarewave. 100 Hz to 3200 Hz to EXT SYNC BNC connector |
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Internal Frequency |
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Jitter (measured pk-pk and presented as a % of a full cycle) inner sector |
blade only: 0.2%; blade + electronics: <7% blade only: 0.2%; blade + electronics: <0.7% |
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Lock indication |
green LED when locked – can be extinguished |
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Setting Time |
<40 s nominal |
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Outputs |
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Sync Out 1 |
10 V pk-pk squarewave at outer sector chopping frequency, 100-3200 Hz |
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Sync Out 2 |
10 V pk-pk squarewave at inter sector chopping frequency – 10-320 Hz |
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Connectors |
BNC |
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Impedance |
10 kΩ. Note that although the output voltage is 10 v pk-pk, the high output impedance means that the outputs can be directly connected to the external reference input of any SIGNAL RECOVERY lock-in amplifier without causing problems. |
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General |
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Power Requirements |
110 V AC, 50/60 Hz or 220/240 V AC, 50/60 Hz supply. State which voltage is required when ordering |
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Dimensions Width Chopper head, overall, inc. |
61/2" (168 mm) 43/4" (122 mm) |
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Options |
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Model 653a |
2 m (6'6") extension cable |
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