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Keysight Technologies
Resistance Measurements Using
the B2900A Series of SMUs
Technical Overview
Keysight B2901A Precision SMU, 1ch, 100 fA resolution,
210 V, 3A DC/10.5 A pulse
Keysight B2902A Precision SMU, 2ch, 100 fA resolution,
210 V, 3A DC/10.5 A pulse
Keysight B2911A Precision SMU, 1ch, 10 fA resolution,
210 V, 3A DC/10.5 A pulse
Keysight B2912A Precision SMU, 2ch, 10 fA resolution,
210 V, 3A DC/10.5 A pulse
Introduction
Keysight Technologies, Inc. B2901/02/11/12A Precision Source/
Measure Unit is a compact and cost-effective bench-top Source/
Measure unit (SMU) with the capability to output and measure
both voltage and current. They cover currents from 10 fA to 3 A
(DC)/10.5 A (pulse) and voltages from 100 nV to 210 V, which
enables you to make a wide range of current versus voltage (IV)
measurements more accurately and quickly than ever before. The
B2900A Series of SMUs also supports a resistance measurement
function that facilitates both low and high resistance
measurements. These features make the B2900A Series of SMUs
the best solution for accurate characterization of resistors and
other devices.
Making accurate resistance measurements is actually one of the
more challenging areas of measurement science. Many factors
can affect the accuracy of a resistance measurement, including
residual test lead resistance, thermal electromotive force and
leakage currents in the measurement path. The B2900A Series
of SMUs possesses a variety of features to address these
measurement issues, including a remote sense function (4-wire
connection), offset compensation, and a guard function. All of
these will be described in greater detail in this technical overview.
What is the B2900A Series of SMUs?
An SMU combines the capabilities of a current source, a voltage source, a
current meter and a voltage meter along with the capability to switch easily
between these various functions into a single instrument (please see Figure 1).
This gives it the ability to evaluate the IV characteristics of devices across all
four measurement quadrants without the need for any additional equipment.
Besides being able to output and measure voltage or current very accurately,
SMUs also possess a compliance feature that allows a limit to be placed on
the voltage or current output to prevent device damage. The members of the
B2900A Series of SMUs are single or dual channel SMU units that offer a wide
range of IV measurement capability for a variety of two-terminal and three-
terminal devices. They cover currents from 10 fA to 3 A (DC)/10.5 A (pulse)
and voltages from 100 nV to 210 V. In addition to their DC operation mode, the
B2900A Series of SMUs also has the ability to perform pulsed measurements
in order to prevent device self-heating from distorting the measurement results.
Finally, the B2900A Series of SMUs also has a built-in resistance measurement
function.
Voltage Current
source meter
A
-
V
-
Current Voltage Source/Measure Unit
source meter (SMU)
Figure 1. The B2900A Series of SMUs combines four measurement functions into a single instrument
Best resistance measurement solution
The B2900A Series of SMUs is the best solution for making accurate resistance
measurements due to its intrinsic voltage/current sourcing and measurement
capabilities. In addition, the B2900A Series of SMUs has some special built-in
functions specifically designed to improve resistance measurement. The
following sections describe these features in detail.
3
Eliminating residual resistance effects
A basic 2-wire connection is the most common scheme used for resistance
measurements. In this configuration (shown in Figure 2a) the same pair of test
leads is used to both force current and measure voltage. This arrangement is
suitable for resistance measurements as long as the residual lead resistance is
negligible compared to the resistance of the device under test (DUT).
However, for very low resistance measurements where the residual lead
resistance is comparable to the DUT resistance, the 2-wire measurement will
give erroneous measurement results (please see Figure 2b). In this case a
4-wire connection scheme (remote sensing) can be used to eliminate this error.
A 4-wire measurement uses one pair of leads to force current and the other pair
of leads to monitor voltage. This eliminates cable resistance effects so that only
the voltage drop across the DUT is measured (please see Figure 2c). In addition,
the 4-wire measurement scheme of the B2900A Series of SMUs keeps the
voltage between the sense points (A and B in Figure 2b) at exactly the specified
voltage Vset, thereby ensuring that your device is characterized exactly under the
measurement conditions you specify. The B2900A Series of SMUs supports both
connection schemes and it is easy to switch between them.
B2901/02/11/12A B2901/02/11/12A B2901/02/11/12A
High force RLead High force
High force High sense IMeas
IMeas IMeas A
VMeas RDUT VMeas RDUT VMeas VSet RLead RDUT
VSet VSet B
Low force Low sense
Low force RLead Low force
VMeas VMeas VMeas
RMeas = ---- = RDUT RMeas = ---- = RDUT + 2