Ametek 7124 Instruction Manual page 139

Figure 5-65, 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 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
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
Chapter 5, FRONT PANEL OPERATION
5-85