Keysight Technologies 3458A Guide D'utilisation page 284

6 Command Reference
– The multimeter multiplies the period of the reference frequency times the
– Query command: The LFREQ? query command returns the present value of
– Related commands: LINE?, NPLC
Example
OUTPUT 722; "LFREQ LINE" !MEASURES LINE FREQUENCY, SETS REFERENCE
!FREQUENCY TO MEASURED VALUE (OR MEASURED
!VALUE/8 FOR 400 HZ LINE FREQUENCY)
LINE?
Line frequency query. Measures and returns the frequency of the AC power line.
Syntax
LINE?
Remarks
– Refer to the
– Related commands: LFREQ
284
you have specified 60 Hz as the reference frequency, the LFREQ? returns
59.99988 (1/.0166667).
specified number of power line cycles (NPLC command) to determine the
actual integration time. The multimeter's normal mode noise rejection (NMR)
specifications for DC and resistance measurements are related to the accuracy
of the A/D converter's reference frequency.
the line frequency reference used by the multimeter's A/D converter. Since the
step size is 100 ns, if the period of the value specified is not evenly divisible by
1/100 ns, the value returned by LFREQ? will be slightly different than the value
specified. Refer to Query commands
information.
LFREQ command on the previous page for an example showing
how to measure the line frequency and automatically set the A/D converter's
reference frequency to the measured value.
near the front of this chapter for more
Keysight 3458A User's Guide