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Section 4: Maintenance
S540 Power Semiconductor Test System Administrative Guide
4-14
S540-924-01 Rev. D / January 2019
Lines should be terminated with newline characters only (
\n
).
Avoid duplicate entries and assignments.
Using NPLCs to adjust speed and accuracy
You can adjust the amount of time that the input signal is measured. Adjustments to the amount of
time affect the usable measurement resolution, the amount of reading noise, and the reading rate of
the instrument.
The amount of time is specified in parameters that are based on the number of power line cycles
(NPLCs). Each power line cycle for 60 Hz is 16.67 ms (1/60); for 50 Hz, it is 20 ms (1/50).
The shortest amount of time results in the fastest reading rate, but increases the reading noise and
decreases the number of usable digits.
The longest amount of time provides the lowest reading noise and more usable digits, but has the
slowest reading rate.
Settings between the fastest and slowest number of PLCs are a compromise between speed and
noise.
Setting the number of power line cycles
The default number of power line cycles (NPLCs) for measurements using the S540 can be set in
several ways:
Specify in the
icconfig_<QMO>.ini
file; your field service engineer (FSE) can change this from
the factory default setting (see
(on page 4-14))
Specify using the
setmode
KI
_
INTGPLC
modifier (see "setmode" and "setmode modifier tables"
in the
Keithley Test Environment (KTE) Programmer's Manual
(part number S500-904-01) for
details); this setting does not persist through a power cycle
The system default NPLC setting is
0.01
. However, this setting differs for some commands,
source-measure unit (SMU) instruments, and ranges. See
(on page 4-15)
for details.