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18 34980A User’s Guide
2 Features and Functions
Measurement Resolution
Resolution is expressed in number of digits the internal DMM can
measure or display on the front panel. You can set the resolution to 4, 5,
or 6 full digits, plus a “½” digit which can be “0” or “1”. To increase the
measurement accuracy and improve noise rejection, select 6½ digits.
To increase the measurement speed, select 4½ digits.
• For ac voltage measurements, the resolution is fixed at 6½ digits.
The only way to control the reading rate for ac measurements is by
changing the channel delay (see page 53) or by setting the ac filter to
the highest frequency limit (see page 36).
• The specified resolution is used for all measurements on the selected
channel. If you have applied Mx+B scaling or have assigned alarms to
the selected channel, those measurements are also made using the
specified resolution. Measurements taken during the Monitor function
also use the specified resolution.
• Changing the number of digits does more than just change the
resolution of the instrument. It also changes the integration time,
which is the period the instrument’s analog- to-digital (A/D) converter
samples the input signal for a measurement. See “Custom A/D
Integration Time” on page 19 for more information.
• The
CONFigure and MEASure? commands contain an optional parameter
which allows you to specify the resolution.
• The instrument returns to 5½ digits when the measurement function is
changed and after a Factory Reset (
*RST command). An Instrument
Preset (SYSTem:PRESet command) or Card Reset (SYSTem:CPON
command) does not change the resolution setting.
Front Panel Operation: DMM or Channel (Configure) > INTEGRATION > NPLC
First, select the measurement function on the active channel. You are
automatically guided to the next level of the menu where you can select a
specific resolution.
Remote Interface Operation: Specify the resolution in the same units as
the measurement function, not in number of digits. For example, if the
function is dc voltage, specify the resolution in volts. For frequency,
specify the resolution in hertz.
You can select the resolution using parameters in the
CONFigure and
MEASure? commands. For example, the following command selects the
10 Vdc range with 4½ digits of resolution on the specified channel.
CONF:VOLT:DC 10,0.001,(@3001)