Stanford Research Systems SR830, Manual

Page: 69 / 177

4-16
Front Panel
[Output]
This key selects the CH2 OUTPUT source. The Channel 2 Output can
provide an analog output proportional to the Display or Y. The output pro-
portional to Y has a bandwidth of 100 kHz (the output is updated at 256
kHz). This output is the traditional Y output of a lock-in. Output propor-
tional to the display (even if the display is simply Y) has a bandwidth of
200 Hz (updated at 512 Hz).
Remember, The Y output has 100 kHz of bandwidth. The Display output
should only be used if the time constant is sufficiently long such that
there are no high frequency outputs.
CH2 Offset and Expand
The Y output may be offset and expanded. Choose Y with the [Display]
key to adjust the Y offset and expand.
The Y analog output is determined by
Output = (signal/sensitivity - offset) x Expand x 10 V
The output is normally 10 V for a full scale signal. The offset subtracts a
percentage of full scale from the output. Expand multiplies the remainder
by a factor from 1, 10 or 100.
Y Output offset IS reflected in displays which depend upon Y.
X and Y offsets do NOT affect the calculation of R or
θ
.
Y Output expand does NOT increase the displayed value Y. Expand
increases the display resolution.
If the display is showing a quantity which is affected by an offset or a
non-unity expand, then the Offset and Expand indicators are turned on
below the display.
See the SR830 Basics section for a complete discussion of scaling, off-
sets and expands.
[Offset On/Off] Pressing this key turns the Y offset on or off. The Offset indicator below
the display turns on when the displayed quantity is offset. This key allows
the offset to be turned on and off without adjusting the actual offset per-
centage.
[Modify] This key displays the Y offset percentage in the Reference Display. Use
the knob to adjust the offset. The Channel 2 display reflects the offset as
it is adjusted while the Reference display shows the actual offset. The
offset ranges from -105.00% to 105.00% of full scale. The offset
percentage does not change with sensitivity - it is an output
function. To return the Reference Display to its original display, press
the desired reference display key ([Phase], [Freq], [Ampl], [Harm #] or
[Aux Out]).
[Auto Offset] Pressing this key automatically sets the Y offset percentage to offset the
Y output to zero.