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Keysight E1412A Digital Multimeter User Guide
Keysight E1412A Multimeter Application Information
Resistance Measurements
Resistance Measurements
The E1412A offers two methods for measuring resistance: 2-wire and 4-wire
ohms. For both methods, the test current flows from the input HI terminal and
then through the resistor being measured. For 2-wire ohms, the voltage drop
across the resistor being measured is sensed internal to the multimeter.
Therefore, input cable resistance is also measured. For 4-wire ohms, separate
“sense” connections are required. Since no current flows in the HI-LO “Sense”
terminal cables, the resistances in these cables do not give a measurement error.
The errors discussed previously for dc voltage measurements also apply to
resistance measurements. Additional error sources unique to resistance
measurements are discussed in the following sections.
4-Wire Ohms Measurements
The 4-wire ohms method provides the most accurate way to measure small
resistances. Errors due to test cable resistances and contact resistances are
reduced using this method. Four-wire ohms is often used in automated test
applications where long cable lengths, numerous connections, or switches exist
between the multimeter and the device-under-test. The recommended
connections for 4-wire ohms measurements are shown below.
Removing Field Wiring Resistance Errors in 2-Wire Ohms Measurements
Field wiring can cause an offset error in 2-wire resistance measurements. You
can use the following procedure to minimize offset errors associated with field
wiring resistance in 2-wire ohms measurements. You short the field wiring at the
DUT location and measure the 2-wire lead resistance. This value is subtracted
from subsequent DUT 2-wire ohms measurements. There are two ways to
effectively null out the lead resistance. The first way is to characterize your field
lead resistance by shorting the leads at the DUT location and measure and
record the lead resistance. Then enable the math operation and store the 2-wire
lead measurement value using the
CALCulate:NULL:OFFSet <
value
>
command
(
CALC:STATe
must be
ON
to do this).
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