Keithley 2657A, Reference Manual, Page: 97 / 805

Model 2657A High Power System SourceMeter® Instrument Reference Manual Section 2: General operation
2657A-901-01 Rev. B/December 2012 2-73
Measure auto delay
The measure delay is a specific delay that is applied before each measurement is taken. This delay is
set to the auto delay setting by default (see table). You can change the default delay by setting the
smuX.measure.delay (on page 7-198) attribute either to a specific value or to an auto delay setting
(set
smua.measure.delay = smua.DELAY_AUTO
). If the measure delay is set to the auto delay
setting, a range-dependent delay is applied each time the instrument performs a current
measurement. This delay also happens for the measurement that is taken after changing current
ranges during an autoranged measurement.
Range Measure auto delay
120 mA 0.1 ms
20 mA 0.1 ms
2 mA 0.5 ms
1 mA 0.5 ms
100
μ
A
1 ms
10
μ
A 1 ms
1
μ
A
2 ms
100 nA 15 ms
10 nA 150 ms
1 nA 1 s
You can increase or decrease the auto delay by changing the delay factor (for example, to reduce the
delay across all ranges by half, set
smua.measure.delayfactor = 0.5
). For additional
information, refer to smuX.measure.delayfactor (on page 7-199) in the "Remote commands" section.
Ranging limitations
If the source and measure functions are different (such as source V and measure I, or source I and
measure V), you can set source and measure ranges separately. If both source and measure
functions are the same, the measure range is locked to the source range.
Manual ranging
Use the range keys, and , to select a fixed range:
•
To set the source range, press the
SRC
key, and then use the
RANGE
keys to set the range.
•
To set the measure range, press the
MEAS
key, and then use the
RANGE
keys to set the range.
If the instrument displays the overflow message on a particular range, select a higher range until an
on-range reading is displayed. To ensure the best accuracy and resolution, use the lowest range
possible that does not cause an overflow.
Autoranging
To use automatic source ranging, press
SRC
then the
AUTO
range key. To use automatic measure
ranging, press the
MEAS
key followed by the
AUTO
range key. The AUTO indicator turns on when
source or measure autoranging is selected. With autoranging selected, the instrument automatically
sets the best range to source or measure the applied signal. The instrument will uprange at 100
percent of the present range.