Filter
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GAIN AND TIME CONSTANT MENU
Max
Reserve
Filter dB/oct.
Sensitivity
10 mV f.s.
Manual
41 dB
100 mS
1.2 Hz
6 12
18 24
60 dB gain
Synchronous
Off
< 200Hz
Manual Reserve
Time Constant
Min
Manual Reserve
Time Constant
Sensitivity
GAIN
TIME CONSTANT
Synchronous
Filter dB/oct
Reserve
Max Min Manual
Gain and Time Cons The Gain and Time Constant menu sets the full scale sensitivity and
dynamic reserve. The low pass filter time constant and slope are also
selected in this menu. See the SR850 Basics section for a discussion of
gain, time constants and dynamic reserve.
Sensitivity The Sensitivity key selects the full scale sensitivity as the active entry
field. Use the knob to adjust the sensitivity. Keypad entry is not allowed
for this parameter. The gain displayed below the sensitivity is the overall
instrument gain, output divided by input. This is simply 10 V (full scale
DC output of X, Y, or R) divided by the sensitivity expressed in dB.
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
resolution of the trace data. Whenever the sensitivity is changed, any dis-
played bar graph will change its range to full scale with zero at the
center.
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.
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