Ametek 7280 Instruction Manual page 147

IE [n] Reference channel source control (Internal/External)
The value of n sets the reference input mode according to the following table:
n Selection
0 INT (internal)
1 EXT LOGIC (external rear panel TTL input)
2 EXT (external front panel analog input)
REFN [n] Reference harmonic mode control
The value of n sets the reference channel to one of the NF modes, or restores it to the
default 1F mode. The value of n is in the range 1 to 32.
REFP[.] [n] Reference phase control
In fixed point mode n sets the phase in millidegrees in the range ±360000.
In floating point mode n sets the phase in degrees.
AQN Auto-Phase (auto quadrature null)
The instrument adjusts the reference phase to maximize the X channel output and
minimize the Y channel output signals.
FRQ[.] Reference frequency meter
If the lock-in amplifier is in the external reference source modes, the FRQ command
causes the lock-in amplifier to respond with 0 if the reference channel is unlocked, or
with the reference input frequency if it is locked.
If the lock-in amplifier is in the internal reference source mode, it responds with the
frequency of the internal oscillator.
In fixed point mode the frequency is in mHz.
In floating point mode the frequency is in Hz.
LOCK System lock control
Updates all frequency-dependent gain and phase correction parameters.
VRLOCK [n] Virtual reference mode lock
The Seek option of the frequency sweep mode must be used before issuing this
command, for which the value of n has the following significance:
n Mode
0 Disables virtual reference mode
1 Enters virtual reference mode by enabling tracking of the signal frequency
Chapter 6, COMPUTER OPERATION
6-13