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6-13
Chapter 6, COMPUTER OPERATION
n Notch filter mode
0 60 Hz (and/or 120 Hz)
1 50 Hz (and/or 100 Hz)
Units made prior to June 1996 generate an Invalid Command (bit 1 of the serial poll
status byte is asserted) to the LINE50 command.
SAMPLE [n] Main analog to digital converter sample rate control
The sampling rate of the main analog to digital converter, which is nominally
166 kHz, may be adjusted from this value to avoid problems caused by the aliasing
of interfering signals into the output passband.
n may be set to 0, 1, 2 or 3, corresponding to four different sampling rates (not
specified) near 166 kHz.
6.4.02 Reference Channel
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)
FNF [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 F mode according to the following table:
n Mode selected
1 The lock-in amplifier measures signals at the reference frequency F
2 The lock-in amplifier measures at 2F
3 The lock-in amplifier measures at 3F
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 output and minimize
the Y output signals.