Resistance Measurement Considerations
The multimeter offers two resistance measurements: 2-wire and 4-wire ohms. For both methods, the test current
flows from the input HI terminal, through the resistor being measured. For 2-wire ohms, the voltage drop across the
resistor being measured is sensed internal to the multimeter. Therefore, test lead resistance is also measured. For 4-
wire ohms, separate "sense" connections are required. Because no current flows in the sense leads, the resistance in
these leads does not give a measurement error.
The errors mentioned earlier in this chapter for DC voltage measurements also apply to resistance
measurements. Additional error sources unique to resistance measurements are discussed below.
The 4-wire ohms method provides the most accurate way to measure small resistances because it reduces test lead
and contact resistances. This is often used in automated test applications where resistive and/or long cable, numerous
connections, or switches exist between the multimeter and the DUT. The recommended connections for 4-wire ohms
measurements are shown below.
Removing Test Lead Resistance Errors
To eliminate offset errors associated with test lead resistance in 2-wire ohms measurements, follow these steps:
Short the test lead ends together and read the displayed test lead resistance.
Press Null. The multimeter will store the test lead resistance as the 2-wire ohms null value, and subtract that value
from subsequent measurements.
See also "Null Measurements."
88 Agilent Truevolt Series DMM Operating and Service Guide
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