Dmm Resistance Measurement Methods - Keithley 2110 Reference Manual

Model 2110 5½ Digit Multimeter Reference Manual

DMM resistance measurement methods

The Model 2110 uses the constant-current method to measure resistance. The constant-current
method sources a constant current (I
(V ). Resistance (R
MEAS
voltage (R
The constant-current method is shown below. The test current sourced to the DUT depends on the
selected measurement range. For example, for the 100 Ω range, the test current is 1 mA. Because
the voltmeter of the Model 2110 has very high input impedance, virtually all the test current (1 mA)
flows through the DUT. For DUT ≤1 kΩ, 4-wire ohms measurements should be used as shown.
Because the voltage is measured at the DUT, voltage drop in the test leads is eliminated (this voltage
could be significant when measuring low-ohm DUT).
Resistance measurement range
100 Ω
1 KΩ
10 KΩ
100 KΩ
1 MΩ
10 MΩ
100 MΩ
The 2-wire constant-current method is shown below.
The 4-wire constant-current method is shown below.
2110-901-01 Rev. C/August 2013
) is then calculated and displayed using the known current and measured
DUT
= V /I ).
DUT MEAS SOUR
Figure 36: Two-wire constant-current source method
) to the device under test (DUT) and measures the voltage
SOUR
Test current
1 mA
1 mA
100 μA
10 μA
1 μA
0.1 μA
0.1 μA
Section 4: Theory of operation
4-3