SRS Labs SR850 - Manual (Page 26)

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4. Press [REF/PHASE]
Press <Sine Output>
Press [.] [5] [ENTER]
5. Press [OUTPUT/OFFSET]
Press <Auto Offset>
Press <Offset>
Press [4] [0] [ENTER]
Press <Expand>
Set the expand to 10 using the knob or the
numeric entry keys.
Display the Reference and Phase menu.
Highlight the sine output amplitude.
Enter an amplitude of 0.5 V. The top display
should show X=0.5 V and the CH1 output should
be 5 V on the DVM.
Display the Output and Offset menu. This menu
chooses which measured parameters or traces
are output on CH1 and CH2. In addition, the X, Y
and R offsets and expands are programmed in this
menu.
The Offset & Expand menu box displays the offset
and expand of either X, Y or R. In this case, the X
offset and expand is displayed. The <X,Y,R> soft-
key selects the which offset and expand is
displayed.
Auto Offset automatically adjusts the Xoffset (or Y
or R) such that X (or Y or R) becomes zero. The
offset should be about 50% in this case. Offsets
are useful for making relative measurements. In
analog lock-ins, offsets were generally used to
remove DC output errors from the lock-in itself.
The SR850 has no DC output errors and the offset
is not required for most measurements.
The offset affects both the displayed value of X
and any analog output proportional to X. The CH1
output should be zero in this case.
The highlighted OFFST indicator turns on at the
bottom left of the top display to indicate that the
displayed trace is affected by an offset.
Highlight the X offset.
Enter an offset of 40% of full scale. The output off-
sets are a percentage of full scale. The percent-
age does not change with the sensitivity. The dis-
played value of X should be 0.100 V (0.5 V - 40%
of full scale). The CH1 output voltage is
(X/Sensitivity - Offset)xExpandx10V.
CH1 Out = (0.5/1.0 - 0.4)x1x10V = 1 V
Highlight the X expand.
With an expand of 10, the display has one more
digit of resolution (100.XX mV).
Outputs, Offsets and Expands