Stanford Research Systems SR830, Manual

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2-11
6. Connect the DVM to the X output on the rear
panel.
7. Connect the DVM to the CH1 OUTPUT on the
front panel again.
Press [Channel 1 Output] to select Display.
Press [Channel 1 Display] to select R.
turn on the OVLD indicator in the Channel 1
display.
With offset and expand, the output voltage gain
and offset can be programmed to provide control
of feedback signals with the proper bias and gain
for a variety of situations.
Offsets add and subtract from the displayed
values while expand increases the resolution of
the display.
The X and Y outputs on the rear panel always pro-
vide voltages proportional to X and Y (with offset
and expand). The X output voltage should be
10 V, just like the CH1 output.
The front panel outputs can be configured to
output different quantities while the rear panel out-
puts always output X and Y.
NOTE:
Outputs proportional to X and Y (rear panel, CH1
or CH2) have 100 kHz of bandwidth. The CH1 and
CH2 outputs, when configured to be proportional
to the displays (even if the display is X or Y) are
updated at 512 Hz and have a 200 Hz bandwidth.
It is important to keep this in mind if you use very
short time constants.
CH1 OUTPUT can be proportional to X or the dis-
play. Choose Display. The display is X so the CH1
output should remain 10.0 V (but its bandwidth is
only 200 Hz instead of 100 kHz).
Let's change CH1 to output R.
The X and Y offset and expand functions are
output functions, they do NOT affect the calcula-
tion of R or
θ
. Thus, Channel 1 (R) should be 0.5V
and the CH1 output voltage should be 5V (1/2 of
full scale).
The Channel 1 offset and expand keys now set
the R offset and expand. The X offset and expand
are still set at 40% and x10 as reflected at the rear
panel X output.
See the DC Outputs and Scaling discussion in the
Lock-In Basics section for more detailed informa-
tion on output scaling.
Outputs, Offsets and Expands