Keithley 2657A, Reference Manual, Page: 55 / 805

Model 2657A High Power System SourceMeter® Instrument Reference Manual Section 2: General operation
2657A-901-01 Rev. B/December 2012 2-31
Ohms ranging
The front panel ohms function does not use ranging. The instrument formats a calculated resistance
reading (V/I) to best fit the display. There may be leading zeros if the ohms reading is less than 1 m
Ω
.
Basic ohms measurement procedure
When you use the MODE key to select ohms measurement, the Model 2657A is automatically
configured as a current source with a level of 1 mA. If you wish to change the source function, source
value, or compliance value (in other words, if you wish to customize the MODE key's standard ohm-
meter's configuration), then perform the following steps to perform ohms measurements. The
following procedure assumes that the Model 2657A is already connected to the device under test
(see
DUT test connections (on page 2-41)).
To take an ohms measurement:
1. Press the
SRC
key to select the source function.
2. Set the output source (current or voltage, dependent on which function is selected) to a value
based on the expected resistance. See Step 1: Select and set the source level (on page 2-24)
earlier in this section.
3. Press the
LIMIT
key to edit the voltage or current limit. When programming a voltage limit, set the
voltage limit above the maximum expected voltage across the resistor under test. When
programming a current limit, set the current limit at or above the maximum expected current
through the resistor under test. See
Step 2: Set the compliance limit (on page 2-24) earlier in this
section.
4. Press the
MEAS
key to display voltage or current.
5. Make sure that AUTO measurement range is on (press the
AUTO
key if needed).
6. Press the
MEAS
key as many times as needed to display ohms.
7. Press the
OUTPUT ON/OFF
control to turn the output on.
8. View the displayed reading (press the
TRIG
key if necessary). When finished, press the
OUTPUT
ON/OFF
control again to turn the output off.
Remote ohms command
Use the
smua.measure.r()
function to obtain a resistance reading. The programming example
below illustrates how to obtain a resistance reading from SMU A:
reading = smua.measure.r()
See Remote source-measure commands (on page 2-25) for more commands necessary to set up
source and measure functions, and Introduction to TSP operation (on page 5-1) for more details.
Ohms programming example
The following programming example illustrates the setup and command sequence of a typical ohms
measurement procedure with the following parameters:
•
Source function: current, 20 mA range, 10 mA output
•
Voltage measure range: auto
•
Voltage compliance: 100 V
•
Sense mode: 4-wire