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Chapter 5, FRONT PANEL OPERATION
5-12
The Reference Channel menu has five controls affecting the instrument's reference
channel. Changes to the setting of these controls can be made by using the adjacent
keys.
REF SOURCE
This control allows selection of the source of reference signal used to drive the
reference circuitry, and has five settings:-
INT
The lock-in amplifier's reference is taken from the instrument's internal
oscillator. Note that this setting gives the best phase and gain measurement
accuracy under all operating conditions, and it is always to be preferred, if
possible, to design the experiment so that the lock-in amplifier acts as the source
of the reference signal.
EXTr RCU
In this setting the reference channel is configured to accept a suitable external
reference source applied to the 7124 RCU rear panel TTL REF IN input
connector
EXTf RCU
In this setting the reference channel is configured to accept a suitable external
reference source applied to the 7124 RCU front panel REF IN input connector
EXTr
In this setting the reference channel is configured to accept a suitable external
reference source applied to the 7124 main console rear panel TTL REF IN input
connector
EXTf
In this setting the reference channel is configured to accept a suitable external
reference source applied to the 7124 main console front panel REF IN input
connector
REF HARMONIC
This control allows selection of the harmonic of the reference frequency at which the
lock-in amplifier will detect. It can be set to any value between 1st and 127th, but
most commonly is set to 1st. Note that the "2F" setting commonly found on other
lock-in amplifiers corresponds to setting this control to 2nd. Adjustment is faster
using the Keypad or Active Cursor controls - see section 4.1.04.
REF PHASE
This control allows the reference phase to be adjusted over the range -180° to +180°
in 1 m° steps.
REF PHASE ±90°
This control allows the reference phase to be adjusted in steps of ±90°.
AUTO PHASE
In an Auto-Phase operation the value of the signal phase with respect to the reference
is computed and an appropriate phase-shift is then introduced into the reference
channel so as to bring the difference between them to zero. The intended result is to
null the output of the Y channel while maximizing the output of the X channel.
Pressing the Previous Menu key returns control to Main Menu 1.
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