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320CD Optical Chopper

Features

 Scitec Instruments Model 320CD is a high stability variable dual frequency optical chopper. The basic system consists of a control unit, a dual frequency chopping head and a set of four chemically blacked photo etched dual frequency discs. This system provides operation over the frequency range 8Hz to 6kHz. A wide selection of additional discs and accessories is available to extend the frequency range and to satisfy individual requirements.

8Hz - 6kHz standard chopping frequency range (0.015Hz option is available)

102mm diameter dual frequency discs

Choice of control units

Compact chopper head

Low noise and vibration

Photochemically etched non-magnetic discs

Variable aperture

Range of accessories

 The 320CDU 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. Two "Reference" BNCs provide TTL level outputs for both the inner and outer set of slots, generated directly from the opto-switches on the chopping head. These signals have constant phase relative to the chopping action and can be used as the reference for other instruments such as lock-in amplifiers.

 The 320H chopping head supplied with the standard system may be bench bolted or optical stalk (bench rod) mounted. Mountings are 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 320D) provides a choice of 4/7, 3/30, 8/60 and 53/60 slots, each having a 1:1 mark to space ratio. Variable apertures can be achieved by mounting two identical discs simultaneously. Additional discs, with up to 60 slots, are available though these are single frequency. Although the standard discs are chemically blacked other finishes, such as gold plating, are available.

Scitec Instruments does not recommend use of discs with greater than 60 slots with the 320 range of optical choppers as the opto-switch will not support these items.

Specifications

320CDU 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. A switch on the back panel selects between inner and outer reference frequencies.

Frequency Stability: Short term - see phase jitter. Long term - ±0.1% of maximum frequency.

Reference output: 5V HCT TTL signal via BNC socket. Outer reference is available on the front panel and the inner reference is available from the back panel.

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: 2.6 kg

320H Chopping Head

Motor: 11 pole DC motor, sleeve bearings with more than 6000 hours lifetime, 0-6000 rpm reversible.

Reference pick-up: Dual IR led and phototransistor pair.

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

320D Set of Chopping Discs

Disc types: 4/7, 3/30, 8/60 and 53/60 slot

Material: Half hard brass, 0.5 mm thick

Diameter: 102 mm

Surface Finish: Chemically blacked

Mark to Space Ratio: 1 to 1 with one blade

r, a, b & d aperturesFrequency Range:

Disc

Frequency (Hz)

Aperture

Phase Jitter, Max

r

a

b

d

300D4/7

Outside
7 slots

17.5 - 700

12.5

22.0

16.4

12.5

±0.7°

Inside
4 slots

10 - 400

12.5

23.2

13.4

12.5

±0.6°

300D3/30

Outside
30 slots

75 - 3000

12.5

5.1

3.8

4.9

±3°

Inside
3 slots

7.5 - 300

12.5

30.9

17.8

12.5

±0.5°

300D8/60

Outside
60 slots

150 - 6000

12.5

2.6

1.9

2.5

±6°

Inside
8 slots

20 - 800

12.5

11.6

6.7

9.6

±1.2°

300D53/60

Outside
60 slots

150 - 6000

15

2.6

1.8

2.5

±6°

Inside
53 slots

130 - 5300

15

1.9

1.0

1.8

±8°

Ordering Information

Model 320CD

 A complete optical chopper system with frequency display includes: 320CDU Control Unit, 320H Chopping Head, 320I Interconnecting Cable, 320D Set of Chopping Discs and IEC mains lead.

Useful Documents

pdf

Model 320CD Datasheet - pdf (68K)

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