Keysight Technologies 3458A Guide D'utilisation page 283

LFREQ
The LFREQ command allows you to specify the A/D converter's reference
frequency or measure the line frequency and set the reference frequency to the
measured value.
Syntax
LFREQ [frequency]
or
LFREQ LINE
frequency
Allows you to specify the reference frequency. The valid range for the frequency
parameter is 45 - 65 Hz, or 360 - 440 Hz. When you specify a frequency in the
range of 360 - 440 Hz, the multimeter divides that value by 8. For example, if you
specify LFREQ 400, the multimeter sets the reference frequency to 400/8 = 50 Hz.
Power-on reference frequency = rounded value of 50 or 60 Hz (see first Remark
below).
Default reference frequency = the exact measured line frequency (or measured
value/8 for 400 Hz line frequency).
LINE
Measures the exact value of the line frequency and sets the reference frequency to
that value (or measured value/8 if the measured value is between 360 and
440 Hz).
Remarks
– When power is applied, the multimeter measures the line frequency, rounds it
– The step size for the period of the reference frequency is 100 ns. For example,
Keysight 3458A User's Guide
to 50 or 60 Hz, and sets the A/D Converter's reference frequency to the
rounded value. (For a 400 Hz power line frequency, the multimeter uses 50 Hz
as a reference frequency which is a subharmonic of 400 Hz.)
the period of a 60 Hz reference frequency is 1/60 Hz = .0166666... Since the
step size is 100 ns, the multimeter uses the value of .0166667 s. The step size
is most noticeable when using the LFREQ? query command. For example, if
Command Reference 6
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