Stanford Research Systems SR830, Manual

Page: 60 / 177

4-7
Front Panel
Sensitivity, Reserve and Time Constants
[Sensitivity Up/Dn]
The [Sensitivity Up] and [Sensitivity Down] keys select the full scale sen-
sitivity. The sensitivity is indicated by 1-2-5 times 1, 10 or 100 with the
appropriate units.
The full scale sensitivity can range from 2 nV to 1 V (rms) or 2 fA to 1 µA
(rms). The sensitivity indication is not changed by the X, Y, or R output
expand. The expand functions increase the output scale as well as the
display resolution.
Changing the sensitivity may change the dynamic reserve. Sensitivity
takes precedence over dynamic reserve. See the next page for more
details.
Auto Gain
Pressing the [AUTO GAIN] key will automatically adjust the sensitivity
based upon the detected signal magnitude (R). Auto Gain may take a
long time if the time constant is very long. If the time constant is greater
than 1 second, Auto Gain will abort.
RESERVE OVLD
The OVLD led in the Sensitivity section indicates that the signal amplifier
is overloaded. Change the sensitivity or increase the dynamic reserve.
[Reserve]
This key selects the reserve mode, either Low Noise, Normal or High
Reserve. The actual reserve (in dB) depends upon the sensitivity. When
the reserve is High, the SR830 automatically selects the maximum
reserve available at the present full scale sensitivity. When the reserve is
Low, the minimum available reserve is selected. Normal is between the
maximum and minimum reserve. Changing the sensitivity may change
the actual reserve, NOT the reserve mode.