Ordering Information
SR540 Optical chopper $1095
O5402530 25/30 dual-slot replacement blade $35
O54056 5/6 dual-slot replacement blade $35
O5405 5-slot replacement blade $35
O54030 30-slot replacement blade $35
O540RCH Replacement chopper head $220
Stanford Research Systems phone: (408)744-9040
www.thinkSRS.com
Chop frequency 4 Hz to 400 Hz (5/6 slot blade)
400 Hz to 3.7 kHz (25/30 slot blade)
Frequency stability 250 ppm/°C (typ.)
Frequency drift <2 %, 100 Hz < f < 3700 Hz
Phase jitter (rms) 0.2° (50 Hz to 400 Hz)
0.5° (400 Hz to 3.7 kHz)
Frequency display 4-digit, 1 Hz resolution and accuracy
Frequency control 10-turn pot with 3 ranges:
4 Hz to 40 Hz
40 Hz to 400 Hz
400 Hz to 3.7 kHz
Input control voltage 0 to 10 VDC for 0 to 100 % of full scale
(Control voltage overrides frequency dial)
Reference modes ƒ
inner
, ƒ
outer
, 5 ׃
outer
, ƒ
inner
+ ƒ
outer
,
ƒ
outer−ƒinner
Dimensions Controller: 7.7" × 1.8" × 5.1" (WHD)
Head: 2.8" × 2.1" × 1.0" (WHD)
Blade diameter 4.04" ± 0.002"
Cable length 6 ft.
Power 12 W, 100/120/220/240 VAC,
50/60 Hz
Warranty One year parts and labor on materials
and workmanship, 90 days on motor
SR540 Specifications
Optical Chopper
SR540 Optical chopper system
The SR540 chopper will handle all your optical chopping
requirementsfrom simple measurements to dual-beam and
intermodulation experiments. The SR540 has a 4-digit
frequency display, front-panel frequency control, analogvoltage frequency control, and two reference outputs with
selectable operating modes. Two anodized aluminum blades
are provided: a 5/6 slot blade for frequencies up to 400 Hz, and
a 25/30 slot blade for frequencies up to 3.7 kHz. Reference
outputs are provided for frequencies corresponding to each
row of slots, as well as the sum and difference frequencies.
www.thinkSRS.com
· 4 Hz to 3.7 kHz chopping frequencies
· Low phase jitter
· Single and dual beam experiments
· Sum & difference reference outputs
· Bolt clamp or rod mounting
· SR540 ... $1095
(U.S. list)
Aperture 0.84" (6-slot)
Aperture 0.62"
(5-slot)
In this application, a single optical beam is chopped by the
outer row of slots, and the reference output from the right
BNC is used to lock the lock-in amplifier to the chop
frequency. The inner row of slots could also be used, in which
case the left BNC would be the reference output. In either
case, the REFERENCE MODE switch is in the “up” position.
Stanford Research Systems phone: (408)744-9040
www.thinkSRS.com
Single-Beam Experiment
In this arrangement, the output from a single source is split
and chopped at two different frequencies by the two rows of
chopper slots. One beam passes through the experiment while
the other is used as a reference beam. The beams are
recombined and sent to the same detector. Two lock-ins are
used to detect the signals at ƒ
inner
, corresponding to the
experimental signal, and ƒ
outer
, corresponding to the reference
beam. If the detected signal in the experimental arm is ratioed
to the detected signal in the control arm, then effects due to
changing source intensity and detector efficiency are removed.
Dual-Beam Experiment
SR540 Optical Chopper
Chop at
Source
Use outer
row of slots
Chopper Wheel
f
Experiment
Chopper Controller
f
Detector
Lock-In Amplifier
Reference Input
Chop at f
Chop at f
Source
inner
Chopper Controller
Chopper Wheel
Control Arm
#1
Detector
ff
inner
Experimental Arm
Lock-In
Amplifiers
f
inner
f
Signals at and
#2
Normalized Signal Out
4.65"
(118 mm)
Aperture 0.170" (30-slot)
Aperture 0.124"
(25-slot)
3.08"
(78.2 mm)
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