Stanford Research Systems SR830 Manual page 66

[Output]
CH1 Offset and Expand
[Offset On/Off]
ment. Pressing this key until the AUX IN leds and the Ratio indicator are
off returns the measurement to non-ratio mode.
This key selects the CH1 OUTPUT source. The Channel 1 Output can
provide an analog output proportional to the Display or X. The output pro-
portional to X has a bandwidth of 100 kHz (the output is updated at 256
kHz). This output is the traditional X output of a lock-in. Output propor-
tional to the display (even if the display is simply X) has a bandwidth of
200 Hz (updated at 512 Hz).
Remember, The X 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.
The X and R outputs may be offset and expanded separately. Choose
either X or R with the [Display] key to adjust the X or R offset and
expand.
X and R analog outputs are 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.
Output offsets ARE reflected in displays which depend upon X or R.
X and Y offsets do NOT affect the calculation of R and θ.
Output expands do NOT increase the displayed values of X or R. 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.
Pressing this key turns the X or R offset (as selected by the [Display]
key) 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 percentage.
[Modify] This key displays the X or R offset percentage (as selected by the
[Display] key) in the Reference Display. Use the knob to adjust the offset.
The Channel 1 display reflects the offset as it is adjusted while the
Reference display shows the actual offset percentage. 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]).
4-13
Front Panel