SFRA45 User Manual
8-6
8.3
Trim mode (TRIM)
The trim function is a powerful and versatile feature that
allows closed loop control of the generator amplitude. It
allows a specific measurement to be programmed for
either CH1 and CH2 and the generator output will be
adjusted to maintain the measured voltage or current. This
allows the excitation level to be controlled over changing
conditions such as a frequency sweep.
AC Trim Data –
Has three options: “
disabled, Ch1 and
Ch2”
AC Level, Tolerance -
At each measurement point, the
measured level is checked against the specified level and
tolerance; if an adjustment is needed the data is discarded
and a new measurement made at the new output level.
The user is alerted to the adjustment by an audible beep.
Particularly important in control loop analysis, where it is
sometimes referred to as amplitude compression, it
prevents the control loop being overdriven as the
frequency changes.
It is also useful in a more general case where test levels
are specified.
Note
When dBm mode level control is selected, the trim
level is entered as dBm but the tolerance remains a linear
percentage of the actual voltage not the logarithmic dBm
measure.
