3-20 Basic DMM Operation Model 2700 Multimeter/Switch System User’s Manual
Resistance measurements (Ω2 and Ω4)
The Model 2700 uses the constant-current method to measure resistance from 100Ω to
1M
Ω. The Model 2700 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 10M
Ω and 100MΩ ranges, the ratiometric method is
used to measure resistance.
Standard resistance measurements — The Model 2700 can make resistance measure-
ments from 100µΩ to 120MΩ. For resistances >1kΩ, the 2-wire (Ω2) method is typically
used for measurements. For resistances
≤1kΩ, the 4-wire (Ω4) measurement method 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 off
-
set voltages, you can use offset compensated ohms on the 100Ω, 1kΩ, and 10kΩ ranges
for the
Ω4 function.
Connections
NOTE 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.
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 and LO, and SENSE Ω4 HI
and LO as shown in
Figure 3-8B.
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