Resistance Measurements (Ω2 And Ω4); Connections - Keithley 2701 User Manual

3-20 Basic DMM Operation
Resistance measurements (Ω2 and Ω4)
The Model 2701 has seven ohms ranges to measure resistance from 100µΩ to 120MΩ .
Available measurement ranges include 100Ω , 1kΩ , 10kΩ , 100kΩ , 1MΩ , 10MΩ , and 100MΩ .
Information for this topic is structured as follows:
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Connections

NOTE
Front panel inputs
Connections for resistance measurements are shown in Figure 3-8. For 2-wire resistance
measurements (Ω2), connect the test leads to INPUT HI and LO as shown in Figure 3-8A.
For 4-wire resistance (Ω4), connect the test leads to INPUT HI, INPUT LO, SENSE Ω4
HI, and SENSE Ω4 LO as shown in Figure 3-8B.
Connections — 2-wire or 4-wire connections can be made to the front panel input
terminals of the mainframe or to a switching module (such as the Model 7700).
Standard resistance measurements — The Model 2701 can make resistance
measurements from 100µΩ to 120MΩ . For resistances >1kΩ , the Ω2 function
(2-wire) is typically used for measurements. For resistances ≤ 1kΩ , the Ω4 function
(4-wire) is typically used. The Ω4 function should be used to cancel the effect of
test lead (and channel path) resistances.
Offset-compensated ohms (OCOMP) — The presence of thermal EMFs (voltages)
can adversely affect low-resistance measurement accuracy. To overcome these
unwanted offset voltages, you can use offset compensated ohms on the 100Ω,
1kΩ, and 10kΩ ranges for the Ω4 function.
Measurement methods — For the 100Ω to 1MΩ ranges, the Model 2701 uses the
constant-current method to measure resistance. The Model 2701 sources a constant
current (I) to the resistance and measures the voltage (V). Resistance (R) is then
calculated (and displayed) using the known current and measured voltage (R = V/
I). For the 10MΩ and 100MΩ ranges, the ratiometric method is used to measure
resistance.
4-wire common-side (CSID) ohms measurements — Explains the CSID ohms
mode which is used with the 7701 module to perform 4-wire common-side ohms
measurements.
When using the front panel inputs, the INPUTS switch must be in the "F" (out)
position. For switching modules, it must be in the "R" (in) position.
Model 2701 User's Manual