Ametek 7280 Instruction Manual page 127

Figure 5-50, Dual Harmonic Reference Menu
The Dual Harmonic Reference 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 three 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.
EXT-R
In this setting the reference channel is configured to accept a suitable external
reference source applied to the rear panel REF TLL input connector
EXT-F
In this setting the reference channel is configured to accept a suitable external
reference source applied to the front panel REF IN input connector
HARMONIC 1
HARMONIC 2
These two controls allow selection of the two harmonics of the reference frequency at
which the lock-in amplifier will detect. They can be set to any value between 1st and
32nd. Adjustment is faster using the Keypad or Active Cursor controls - see section
4.1.04.
HARMONIC 1 PHASE
HARMONIC 2 PHASE
These two controls allow the reference phase of harmonic
independently adjusted over the range -180° to +180° in 10m° steps. Adjustment is
Chapter 5, FRONT PANEL OPERATION
and harmonic
1
to be
2
5-81