Stanford Research Systems SR830 Manual page 70

Front Panel
[Expand] Pressing this key selects the Y Expand. The expand can be 1 (no
expand), 10 or 100. If the expand is 10 or 100, the Expand indicator
below the display will turn on. The output can never exceed full scale
when expanded. For example, if an output is 10% of full scale, the
largest expand (with no offset) which does not overload is 10. An output
expanded beyond full scale will be overloaded.
Short Time Constant Limitations
A short time constant places a limit on the total amount of DC gain
(reserve plus expand) available. If the time constant is short, the filter
slope low and the dynamic reserve high, then increasing the expand may
change the time constant. See the table of time constants and DC gains
in the Gain and Time Constant section.
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