Stanford Research Systems SR124, Руководство по эксплуатации и обслуживанию

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2.3 Navigating the front panel 2 – 11
2.2.4.2 AC Volt mode
When phase-sensitive detection is not possible, the SR124 can be
configured for AC Volt mode. In this setting, the reference oscillator
is unused and the phase-sensitive detector (square wave mixer) is
controlled directly by the polarity of the amplified AC input signal.
The instrument now acts as an averaging AC voltmeter, where the
detection element is an absolute value detector.
For most applications using AC Volt mode, the Reserve setting
should be set to Low Noise, since there is no reserve benefit from
the mixer in this configuration. If the input signal is not already rel-
atively clean with high signal-to-noise, the input filter may be used
to define the frequency band for measurement.
2.3 Navigating the front panel
The front panel of the SR124 is organized into distinct functional
sections. Knowing this organization will help you to become familiar
with its operation. A diagram of the entire front panel is in Figure 2.2,
below.
Local
Model SR124 Analog Lock-In Amplifier
CONTROL INHIBIT
SETUP
AUTO
Stanford Research Systems
RESERVE
SENSITIVITY
SIGNAL INPUT
INPUT FILTER
OUTPUT
REFERENCE
100
200
500
A
A/I B
Signal
Monitor
nV
mV
Q-factor
Time Constant
µV
AC
DC
10 MΩ 10 MΩ 600 Ω 50 Ω
Ground
Flat
Notch
Low Noise
Normal
High Res.
12dB/oct.
6dB/oct.
Low Pass
fine
coarse
High Pass
Band Pass
Float
OVLD
OVLD
On AC Volt
Lock-In
INHIBITED
CPU Activity
TTL
90
3f
0
2.0k 210k
On
Square
Sine
200 21k
20 2.1k
2.0 210
0.2 21
180 90
270 180
270 360
Unlocked
Remote Activity
OFFSET OUTPUT
DC Bias
Range (Hz)
Mode
Ref. Out
Ext. In
Quadrant
OVLD
A–B
I (10
6
)
I (10
8
)
1
1
1
2
5
10
20
50
100
2
2
5
5 10
10
20
20
50
50
100
100
200
200
500
500
Push to select
Hold to
null
depth
f trim
1
1
3
3
10
10
30
30
100
100
300
300
All CPU clocks, panel
controls, and remote
commands disabled
min
ms
s
2f External
f
Internal
Push for
Ext. In TTL
Rear VCO
kHz
Hz
PHASE FREQ AMPL BIAS OFFSET
kHz V
mV
%
Hz
deg
OVLD
REM
Push to select
Hold to
null
600 Ω
10% ENBW
Input Ground
Type Reserve
Slope On/Off
Modify
Mode
Phase Gain
Offset Lock
Assist
Save Recall
Phase Freq Ampl
On/Off
Modify
Shape
Couple
BNC
knob
knob
knob
knob
knob
switch
knob
knob
knob
BNC BNC BNC BNC BNC
Figure 2.2: The SR124 front panel.
In Figure 2.2, the two large rectangular blocks above “INPUT FIL-
TER” and “REFERENCE” are static numeric displays. The larger
white rectangle in the upper center of the drawing is the jewel bear-
ing analog panel meter.
The two large knobs each have a push-button secondary function;
in addition to adjusting the parameter currently “in focus” (more
about that later), briefly pressing the knob inward has a secondary
function. Also, holding the knob in for several seconds has a tertiary
function—clearing or nulling the parameter in focus.
SR124 Analog Lock-In Amplifier