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Section Topics
2400S-903-01 Rev. E / September 2011
Section 1: Introduction
Series 2400 SourceMeter® Quick Start Guide
Offset-compensated ohms
Thermal EMFs can corrupt low-resistance measurements. An offset-compensated
Ω
measurement cancels out unwanted offset by performing the following 2-point measurement
process:
Offset-Compensated
Ω
=
Δ
V /
Δ
I
where:
Δ
V = V2 - V1
Δ
I = I2 - I1
V1 and I1 are V and I measurements with the source set to a specific level.
V2 and I2 are V and I measurements with the source set to zero.
1.
Select
the
Ω
function, and select the auto or manual ohms measurement method.
2.
Enable offset compensation by using the following menu sequence:
3.
Press CONFIG > press MEAS
Ω
> select OFFSET COMPENSATION > select ENABLE
4.
If using auto ohms, go to the next step. For manual ohms, configure the desired source (V
or I) to output an appropriate source level. Set compliance and select a measurement range
(or use auto range).
5.
Turn the output on and observe the offset-compensated ohms reading on the display. Note
that the source value alternates between the set output level and zero.
6.
When finished, turn the output off and disable offset compensation.
NOTE Manual offset-compensated ohms is also available as a math
function (FCTN). This math function allows you to specify both source
levels (see “Math functions” in “Features to enhance DUT testing.”
In-circuit ohms measurements
Ohms guard allows you make accurate in-circuit ohms measurements on resistor networks. These
measurements are covered in
Advanced operation
.
Remote command programming
Data string
The :READ? command is typically used to trigger a source-measure action and request the data
string. The data string is sent to the computer when the SourceMeter is addressed to talk.
The data string is typically made up of five elements separated by commas. The first element is
the voltage reading, the second is the current reading, and the third is the resistance reading. For
voltage and current, the reading could be source or measure depending on how the instrument is
configured. For example, if sourcing voltage and measuring current, the voltage element is the
source reading and the current element is the measured reading. The NAN (not a number) value
of +9.91e37 is used for a function that is not enabled.
The fourth data element is the timestamp and the fifth is the status word. See Section 18,
FORMat
subsystem,
of the 2400 Series SourceMeter User’s Manual for details on all aspects of the data
format.
