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30 HP E1312A/E1412A Multimeter Application Information Chapter 2
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).
The following program shows SCPI examples used to store a
NULL value.
CONF:RES Set to 2-wire ohms function.
Short the lead resistance at the DUT location.
READ? Measure the 2-wire ohms lead resistance.
Enter lead resistance value into computer.
CALCulate:FUNCtion NULL Set math operation to NULL.
CALCulate:STATe ON Turn math operation ON.
CALCulate:NULL:OFFSet <value> Store the NULL offset value.
Subsequent 2-wire ohms measurements will subtract the null offset value
from the measurement thereby removing the lead resistance from the
measurement.
The second way to store the 2-wire lead resistance as the
NULL offset value
is to let the multimeter automatically do this with the first measurement. The
first measurement made after
CALCulate function is set to NULL and the
STATe is set to ON stores the measured value as the null offset.
CONF:RES Set to 2-wire ohms function.
Short the lead resistance at the DUT location.
CALCulate:FUNCtion NULL Set math operation to NULL.
CALCulate:STATe ON Turn math operation ON.
READ? Measure the 2-wire ohms lead resistance.
Enter lead resistance value into computer. The value is automatically
stored in the multimeter’s null offset register.
Remove the short from the lead resistance at the DUT location
and connect leads to your DUT.
READ? Make a 2-wire ohms resistance measurement.
Enter lead resistance value into computer. The NULL value is
subtracted from the measurement to more accurately provide the
DUT resistance.