Keysight Technologies 3458A Guide D'utilisation page 101

Configuring for Measurements 3
The specified AC voltage measurement method remains in effect until power is
cycled, the multimeter is reset, or another method is specified. Whenever you
select AC or AC+DC voltage measurements, the last specified (or power-on)
measurement method will be used.
AC or AC+DC current
The multimeter measures current by placing an internal shunt resistor across the
input terminals, measuring the voltage across the resistor, and calculating the
current (current =voltage/resistance). Unlike AC or AC+DC voltage
measurements, AC or AC+DC current measurements can be made using the
analog method (direct integration) only. The multimeter's front and rear current
inputs are protected by 1 A, 250 V fuses. Figure 3-2 shows the front terminal
connections for all types of current measurements.
The multimeter measures AC or AC+DC current on any of five ranges. For AC
current measurements, the multimeter measures only the AC component of the
input signal, For AC+DC current measurements, the multimeter measures the DC
component and the AC component with frequencies >10 Hz. Notice that when
measuring AC+DC current, any AC components below 10 Hz are not included in
the measurement. The maximum resolution for AC or AC+DC current is 6½, digits.
Table 3-8 shows each current range and its full scale reading, maximum
resolution, and the shunt resistor used. (Resolution is a function of the specified
integration time; refer to Setting the integration time, later in this section, for
more information.) You specify AC current measurements using the ACI command
or AC+DC current measurements using the ACDCI command. For example to
specify AC current measurements on the 100 µA range, send:
OUTPUT 722;"ACI 100E-6"
To specify AC+DC current measurements on the 10 mA range, send:
OUTPUT 722;"ACDCI 10E-3"
Keysight 3458A User's Guide 101