Ametek 7270 Instruction Manual page 131

Figure 5-62, 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-rp
In this setting the reference channel is configured to accept a suitable external
reference source applied to the rear panel TTL REF IN input connector
EXT-fp
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 and 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 127th.
HARMONIC 1 PHASE and 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
faster using the Keypad or Active Cursor controls - see section 4.1.04.
The Auto-Phase1 and Auto-Phase 2 functions (see section 5.6.08) also affect the
settings of these controls.
Pressing the Previous Menu key returns control to Main Menu 1.
Chapter 5, FRONT PANEL OPERATION
and harmonic
1
to be
2
5-83