Keysight Technologies 34410A - 2-Wire Vs. 4-Wire Measurements; Auto Zero On;Off; Integration; NULL Reading

118 34410A/11A/L4411A User’s Guide
4 Measurement Tutorial
• Choice of four–wire or two–wire technique affects measurement accuracy.
• Use of the auto zero feature affects measurement speed and accuracy.
• Choice of integration (measurement time) setting affects measurement accuracy and
power–line noise rejection.
• Use of the offset compensation feature can eliminate residual voltages in the test
instrumentation or circuit.
Probe Type Choice
RTD's provide very accurate, highly linear relationships between resistance and
temperature, over a range of roughly –200 to 500
o
C. There is very little conversion
complexity for an RTD since it is so intrinsically linear. The multimeter provides
measurement for the IEC751 standard RTD, which has a sensitivity of 0.00385/
o
C.
Thermistors consist of semiconductor materials, and provide roughly
10 times the sensitivity of the RTD. Because they are semiconductors, their temperature
range is more limited, commonly to –80
o
C to 150
o
C. Thermistors have highly
non–linear temperature–resistance relationships; therefore their conversion algorithms
are more complex. The Keysight multimeters use the standard Hart–Steinhart
Approximation to provide accurate conversions, with a typical resolution of 0.08
o
C.
2–Wire vs. 4–Wire Measurements
As with resistance measurements, four–wire temperature measurements are more
accurate, since errors due to lead wire resistance are completely eliminated. Alternately,
you can use the multimeter’s Null function to remove the test lead resistance from the
measurement (see “NULL Reading:” on page 119).
Auto Zero On/Off
Enabling the auto zero feature (ON) provides greater accuracy; however, the additional
measurement (of zero) reduces 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 34411A/L4411A), 0.006, 0.06,
0.02, 0.2, 1, 2, 10 and 100.