LINE?
192 Chapter 6 Command Reference
Default reference frequency = the exact measured line frequency (or measured
value/8 for 400Hz 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
440Hz).
Remarks • When power is applied, the multimeter measures the line frequency, rounds it
to 50 or 60Hz, and sets the A/D Converter's reference frequency to the rounded
value. (For a 400Hz power line frequency, the multimeter uses 50Hz as a
reference frequency which is a subharmonic of 400Hz.)
• The step size for the period of the reference frequency is 100ns. For example,
the period of a 60Hz reference frequency is 1/60Hz = .0166666... Since the step
size is 100ns, the multimeter uses the value of .0166667s. The step size is most
noticeable when using the LFREQ? query command. For example, if you have
specified 60Hz as the reference frequency, the LFREQ? returns 59.99988
(1/.0166667).
• The multimeter multiplies the period of the reference frequency times the
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.
• Query Command. The LFREQ? query command returns the present value of
the line frequency reference used by the multimeter's A/D converter. Since the
step size is 100ns, if the period of the value specified is not evenly divisible by
l/l00ns, the value returned by LFREQ? will be slightly different than the value
specified. Refer to "Query Commands" near the front of this chapter for more
information.
• Related Commands: LINE?, NPLC
Example OUTPUT 722; "LFREQ LINE"!MEASURES LINE FREQUENCY, SETS REFERENCE
!FREQUENCY TO MEASURED VALUE (OR MEASURED
!VALUE/8 FOR 400HZ LINE FREQUENCY)
LINE?
Line Frequency Query. Measures and returns the frequency of the AC power
line.
Syntax LINE?
Remarks • Refer to the LFREQ command on the previous page for an example showing
how to measure the line frequency and automatically set the A/D converter's
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