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Section 2: General operation
2606B System SourceMeter® Instrument Reference Manual
2-76
2606B-901-01 Rev. B / May 2018
Speed
The SPEED key on the virtual front panel sets the integration time, or measurement aperture, of the
A/D converter (period the input signal is measured). The integration time affects the usable digits, the
amount of reading noise, and the reading rate of the instrument. The integration time is specified in
parameters based on the number of power line cycles (NPLC), where 1 PLC for 60 Hz is 16.67 ms
(1/60) and 1 PLC for 50 Hz is 20 ms (1/50).
In general, the fastest integration time (0.001 PLC) results in the fastest reading rate, but also causes
increased reading noise and fewer usable digits. The slowest integration time (25 PLC) provides the
best common-mode and normal-mode noise rejection, but has the slowest reading rate. Settings
between the fastest and slowest integration times are a compromise between speed and noise. The
default power-on speed setting is NORMAL (1 PLC).
Setting speed
Speed is set from the SPEED configuration menu and is structured as follows.
Front-panel speed configuration
Press the
SPEED
key (or use the CONFIG menu) to display the following menu items:
•
FAST:
Sets the measurement speed to 0.01 PLC (fast performance, but accuracy is reduced)
•
MED:
Sets the measurement speed to 0.10 PLC (speed and accuracy are balanced)
•
NORMAL:
Sets the measurement speed to 1.00 PLC (speed and accuracy are balanced)
•
HI-ACCURACY:
Sets the measurement speed to 10.00 PLC (high accuracy, but speed is
reduced)
•
OTHER:
Sets the measurement speed to any PLC value from 0.001 to 25
Remote speed programming
Speed command
The following table shows the command that controls speed. See the
page 7-1) for more information.
Speed command*
Command**
Description
smu
X
.measure.nplc = nplc
Sets the speed of the ADC (nplc = 0.001 to 25).
* The speed setting is global and affects all measurement functions.
* * smu
X
can be
smua
for SMU Channel A or
smub
for SMU Channel B
Speed programming example
Use the NPLC command to set the speed of the integrating analog-to-digital converter (ADC). The
programming example below illustrates how to set the speed to 10 PLC:
-- Set NPLC to 10.
smua.measure.nplc = 10