Automatic Level Control - Keysight E4980A User Manual

Configuring Measurement Conditions (Display and Function Related Settings)
MEAS SETUP page

Automatic level control

Functional Description
The automatic level control (ALC) feature adjusts the voltage across the DUT to
the same level as the signal voltage level setting or the current across the DUT
to the same level as the signal current level setting. Using this feature, you can
maintain a constant level (voltage or current) of measurement signals applied
to the DUT.
The automatic level control feature uses a monitorable feedback circuit, as
shown in
measurement and level change, two to nine times every measurement cycle.
(The time required for level adjustment depends on how many times the
feedback loop is iterated (the value "n") and, in turn, the value "n" depends on
the characteristics of the DUT. Generally, the higher the DUT's non-linearity,
the longer the level adjustment time.)
If the automatic level control feature fails to complete the level adjustment
after it has iterated the feedback loop (level measurement and level change)
nine times, it becomes inactive
regulate" appears. In this case, the signal input level is made equal to the
specified level, and the signal output level is made equal to the output level
with the automatic level control feature turned off.
The time required for the automatic level control feature to complete the
adjustment can be determined based on the following formula:
When the measurement range is set to HOLD, (measurement time + test signal
voltage setting time)  n,
where n = 2 (min)
n = 9 (max)
For more on the test signal voltage setting time, refer to data sheet in
Chapter 11 "Specifications and Supplemental Information"
1. If the DUT has a very high linearity, the automatic level control feature may turn inactive
Keysight E4980A/AL Precision LCR Meter
Figure 4-3, to iterate a feedback loop that consists of level
before it enters the 9th iteration of the feedback loop of the level measurement cycle and
the level may change.
1
and the warning message "ALC unable to
.
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