5
3 Using the Chopper 16
3.1 How the Model 3502 Optical Chopper Works ................................................. 16
3.2 Mounting the Unit............................................................................................. 17
3.2.1 Chopper Head ........................................................................................... 17
3.2.2 Chopper Motor.......................................................................................... 19
3.2.3 Mounting a Wheel..................................................................................... 19
3.2.4 Mounting the Wheel Cover....................................................................... 21
3.3 Rack Mount Option .......................................................................................... 22
3.4 Initial Setup....................................................................................................... 22
3.4.1 Power ........................................................................................................ 23
3.4.2 Connecting the Chopper Head to the Chopper Controller........................ 23
3.4.3 Connecting the Chopper Controller to a Computer via USB ................... 23
3.5 Operation .......................................................................................................... 23
3.5.1 Front Panel Operation ............................................................................... 24
3.6 Back Panel Operation ....................................................................................... 30
4 Computer Interfacing 32
4.1 Introduction....................................................................................................... 32
4.2 Using the Graphical User Interface (GUI)........................................................ 32
4.2.1 A Quick Start: How to Use the ‘New Focus Chopper Application’......... 33
4.3 USB Communication........................................................................................ 34
4.4 Command Index and Conventions.................................................................... 34
4.5 Command Description ...................................................................................... 36
5 Troubleshooting 43
5.1 Normal Startup Operation................................................................................. 43
5.2 Symptoms and Steps to Follow ........................................................................ 43
6 Specifications 45
6.1 Chopping Frequency......................................................................................... 45
6.2 Internal Synthesizer .......................................................................................... 45
6.3 Reference Input................................................................................................. 45
6.4 Reference Output .............................................................................................. 46
6.5 Phase Shifter ..................................................................................................... 46
