SRS Labs SR850 - Manual (Page 21)

2-9
Displays and Traces
[AUTO SCALE] automatically scales the active
display. In this case, the trace data is moving and
autoscaling may not do a very satisfactory job.
To manually set the graph scale, you set the range
(±) and center value (@). The graph displays a
scale equal to the center value plus and minus the
range.
In this case, set the bar graph to ±180°. The bar
graph should be a linear phase ramp at 0.2 Hz.
The monitor display at the top of the screen moni-
tors either the lock-in settings (sensitivity, time
constant, etc.) or the measured lock-in inputs and
outputs (X, Y, R,
θ
and Aux In 1-4).
The Input/Output monitor allows you to see all of
the measured quantities, even if they are not
shown on the larger displays.
The screen is now setup for a single display. The
default display type for the full screen display is a
polar graph.
The polar graph plots the quantities X and Y on an
X-Y axis. The resulting vector has a length equal
to the magnitude R and has a phase angle relative
to the positive X axis equal to
θ
. In this case, since
the phase is rotating at the difference frequency,
the vector rotates at 0.2 Hz.
Display the Reference and Phase menu.
Highlight the internal oscillator frequency.
As the internal reference frequency gets closer to
the signal frequency, the rotation gets slower and
slower. If the frequencies are EXACTLY equal,
then the phase is constant.
By using the signal source as the external refer-
ence, the lock-in will phase lock its internal oscilla-
tor to the signal frequency and the phase will be a
constant.
Highlight the reference source.
Select external reference mode. The lock-in will
phase lock to the signal at the Reference Input.
Press [AUTO SCALE]
Press the <± Range> softkey. This is the fifth
softkey from the top.
Press [1] [8] [0] [ENTER]
6. Press <Monitor> to select Input/Output.
7. Press <Format> to select Single.
8. Press [REF/PHASE]
Press <Ref. Frequency>
Use the knob to adjust the frequency slowly to
try to stop the rotation of the signal vector.
9. Use a BNC cable to connect the TTL SYNC
output from the generator to the Reference
Input of the lock-in.
Press <Ref. Source>
Use the knob to select External.