Stanford Research Systems SR124, Operation And Service Manual

Page: 42 / 85

2 – 20 Introduction
2.3.4.3 Mode
The Mode knob selects the reference oscillator mode. Possible selec-
tions are Rear VCO , Internal , f External , 2f External , and 3f External .
( FMOD , 4 – 9 )
The Mode knob also controls the Ext. In configuration between sine
and TTL modes. Pressing Mode inwards toggles between the two
states, as indicated by the TTL indicator in the Ext. In sub-section.
( RSLP , 4 – 10 )
2.3.4.4 Range
The Range knob selects the reference oscillator frequency range.
Ranges each span 2 decades, and overlap by one decade each.
(
FRNG
, 4 – 10 )
2.3.4.5 DC Bias
Pressing the [On
/
O
ff
] button in the DC Bias block toggles the bias on
and o
ff
for the reference output signal. ( BION , 4 – 11 )
Depending on the current value of the reference amplitude and bias,
the bias might not be allowed to turn on. Full details of the interde-
pendence of DC Bias and amplitude can be found in section 3.4.
Pressing the [Modify] button within DC Bias brings the display focus
to
BIAS . The bias setting can be adjusted by turning REFERENCE ;
however, the bias will not be added to the reference output unless it
is enabled with the [On
/
O
ff
] button. ( BIAS , 4 – 11 )
2.3.4.6 Ref. Out
The Ref. Out BNC connector provides the refence output signal. The
RMS amplitude of the signal is adjusted with the
AMPL parameter.
Pressing [Shape] toggles between sine output and square output.
(
FORM , 4 – 11 )
SR124 Analog Lock-In Amplifier