Keysight U2741A Guide D'utilisation page 52

3 Measurement Tutorial
Resistance Measurement Considerations
When measuring resistance, the test current flows from the input HI terminal
through the resistor being measured. The voltage drop across the resistor being
measured is sensed internally in the digital multimeter. Therefore, the test lead
resistance is also measured.
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 here.
Resistance measurements
The Keysight U2741A 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 digital
multimeter. Therefore, test lead resistance is also measured. For 4-wire ohms,
separate "sense" connections are required. Since 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 on the following pages.
4-wire ohms measurements
The 4-wire ohms method provides the most accurate way to measure small
resistances. Test lead resistances and contact resistances are automatically
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 digital multimeter and the device-under-test. The recommended
connections for 4-wire ohms measurements are shown below.
52 Keysight U2741A User's Guide