Stanford Research Systems SR810 Manual page 18

X and R
Press [Channel 1 Display] to select X again.
5. 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.
The phase (q) between the reference and the signal
changes by 360° approximately every 5 sec (0.2 Hz
difference frequency). The value of q can read via the
computer interface.
Change the display back to X (slowly oscillating).
By using the signal generator as the external
reference, the lock-in will phase lock its internal
oscillator 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 value of X should be
steady. The actual value 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 (successfully locked
to the external reference).
The display may be stored in the internal data buffer at
a programmable sampling rate. This allows storage of
8k points. See the Programming section for more
details.
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