Stanford Research Systems SR830 Manual page 19

θ
X, Y, R and
4. Press [Channel 1 Display] to select R.
5. Press [Channel 2 Display] to select θ.
6. Press [Freq]
Use the knob to adjust the frequency slowly to
try to stop the rotation of the phase.
7. Use a BNC cable to connect the TTL SYNC
output from the generator to the Reference
Input of the lock-in.
Press [Source] to turn the INTERNAL led off.
Press [Trig] to select POS EDGE.
should now oscillate at about 0.2 Hz (the accuracy
is determined by the crystals of the generator and
the lock-in).
The default Channel 1 display is X. Change the
display to show R. R is phase independent so it
shows a steady value (close to 0.500 V).
The default Channel 2 display is Y. Change the
display to show θ. The phase between the refer-
ence and the signal changes by 360° approximate-
ly every 5 sec (0.2 Hz difference frequency).
The bar graph in this case is scaled to ±180°. The
bar graph should be a linear phase ramp at
0.2 Hz.
Show the internal oscillator frequency.
As the internal reference frequency gets closer to
the signal frequency, the phase rotation gets
slower and slower. If the frequencies are
EXACTLY equal, then the phase is constant.
By using the signal generator 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.
Select external reference mode. The lock-in will
phase lock to the signal at the Reference Input.
With a TTL reference signal, the slope needs to be
set to either rising or falling edge.
The phase is now constant. The actual phase
depends upon the phase difference between the
function output and the sync output from the
generator.
The external reference frequency (as measured by
the lock-in) is displayed on the Reference display.
The UNLOCK indicator should be OFF (success-
fully locked to the external reference).
The displays may be stored in the internal data
buffers at a programmable sampling rate. This
allows storage of 16000 points of both displays.
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