Stanford Research Systems SR865A, Operation Manual

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Chapter 3 Operation 75
SR865A DSP Lock-in Amplifier
Numeric entry is straightforward. {Close} will return to the data screen. The buttons
{F1}, {F2}, {F3} and {F4} are frequency presets. Touching a preset will load the preset
value immediately. Touch and hold a preset button to memorize the current setting. Other
parameters may have slightly different entry screens.
Source [Ref/ chop ]
Press this key briefly to cycle through the reference sources. Press and hold to display the
SR540 Chopper setup screen (see Chop, below).
Internal
When the source is Internal, the SR865A's synthesized internal oscillator is used as the
reference. The Ref In BNC is ignored in this case. The internal frequency is shown in the
info bar. Use the <Frequency> knob or the numeric keypad to adjust the frequency.
In this mode, the Sine Out is at the internal frequency.
External
When the source is External, the SR865A will phase lock to the external reference
provided at the Ref In BNC. The SR865A will lock to frequencies between 0.001 Hz and
4 MHz. The external frequency is shown in the info bar. The <Frequency> knob has no
effect on the external frequency.
In this mode, the Sine Out is at the external frequency.
Dual
When the source is Dual, the SR865A will detect signals at f
detect
= |f
int
− f
ext
| where f
ext
is
the external reference frequency and f
int
is the internal frequency. The internal frequency
is shown in the info bar. Use the <Frequency> knob or the numeric keypad to adjust the
internal frequency.
In this mode, the Sine Out is at the internal frequency.
To record and view the external frequency, use the [Config] key to assign f
ext
to one of
the four data channels.
You can find more about dual reference mode in Appendix E (page 175).