Stanford Research Systems SR844 User Manual page 21

15 Connect the Sync output of the signal
generator to the REF IN connector of the
SR844 with a BNC cable.
Note: If you are using a signal generator with
a single output, split the output using a BNC
Tee, or a power splitter or 10 to 20 dB
directional coupler. (If you use a directional
coupler the straight-through output should go
to REF IN and the coupled output should go
to the SIGNAL IN.) You may need to adjust
the signal generator amplitude to provide the
SR844 with enough signal to lock, and you
may need to adjust the SR844 sensitivity so
that the signal amplitude, R, is a sizable
fraction of the full scale range.
16 Change the signal generator frequency to 1.00
MHz.
X, Y, R, θ θ θ θ and dBm 1-11
The SR844 locks to the signal generator frequency,
θ
and the R and displays are both stable. Check that
the UNLOCK error indicator (above the knob) is
off.
If the REF IN signal is noisy or too small, the
SR844 may not be able to lock. The reference
signal should be greater than 0.6 Vpp. If the signal
generator Sync output cannot drive 50
enough amplitude, try changing the Reference Input
Ω Ω Ω Ω
Impedance to 10 k by pressing the Ref Z-In key.
The SR844 UNLOCK error indicator comes on
briefly, then goes off to indicate that the SR844 has
locked to the new frequency. The new frequency
should be correctly displayed in the Reference
display.
The displayed value of R should not change
(depending upon the amplitude flatness of the signal
generator and the accuracy of the SR844). The
θ
value of may change a few degrees depending
upon the signal generator Sync phase and cable
lengths.
SR844 RF Lock-In Amplifier
Ω
to a large