34410A/11A User’s Guide 113
Measurement Tutorial 4
Auto Zero On/Off
Enabling the auto zero feature (ON) provides greater accuracy; however,
the additional measurement will reduce the reading speed.
Integration
There are two methods of integrating the sampled data taken in the
measurement, NPLC's and Aperture.
NPLC's sets the number of power line cycles in the gating of the
measurement. The range of choices for NPLC includes 0.001 and 0.002 (for
model 34411A only), 0.006, 0.06, 0.02, 0.2, 1, 2, 10 and 100.
The fractional NPLC values offer faster measurements, at the expense of
some time integration accuracy. When you set the NPLC to 1 or more, you
not only achieve improved accuracy associated with time averaging, but
also achieve rejection of the power–line interference (normal mode
rejection, or NMR); the greater the integral NPLC value, the larger the
NMR.
Aperture is the period, measured in seconds, during which the
multimeter's analog–to–digital (A/D) converter samples the input signal for
a measurement. A longer aperture yields better resolution; a shorter
aperture provides for faster measurements. This selectable feature allows
the user to set a specific measurement period, not based on power line
frequency. Selectable values range from 300 ms to 1s for the 34410A, and
from 300 ms to 1s for the 34411A. Setting an aperture value provides no
NMR.
Offset Compensation
With offset compensation enabled (ON), the multimeter makes a normal
temperature measurement first, followed by a second measurement to
determine any offset voltage in the input circuitry. The resultant displayed
measurement corrects for this offset. Enabling offset compensation
increases measurement time.
NULL Reading:
The multimeter allows a separate null setting to be saved for the
temperature function. When making null measurements, each reading is
the difference between a stored null value and the input signal. One
application of NULL is to increase accuracy of two–wire resistance
measurements by first nulling the closed–circuit test lead resistance.
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