Stanford Research Systems SR844 User Manual page 20

1-10 X, Y, R, θ θ θ θ and dBm
6 Connect the signal generator output to the
SR844 SIGNAL IN connector with a BNC
cable.
7 Adjust the signal generator frequency if
necessary to better match the signal generator
frequency to the SR844.
8 Adjust the signal generator frequency in steps
of 1 Hz (or less) until the CH1 and CH2
readings oscillate with a period of a few
seconds.
Press CH1 Display once to select R [V].
9
10 Press CH1 Display to select R [dBm].
11 Adjust the signal generator amplitude to half
the original amplitude (100 mVrms, –6 dBm,
or 300 mVpp).
Press CH1 Display several times until R [V]
12
is selected once again.
Press CH2 Display to select
13
Press the Source key (above REF OUT).
14
SR844 RF Lock-In Amplifier
The CH1 and CH2 readings should both vary
between positive and negative values in a correlated
fashion that reflects the changing relative phase
between the two instruments.
The extent of adjustment should be less than 10 Hz.
The CH1 and CH2 display bargraphs should now
oscillate slowly.
R is the signal amplitude and is independent of
reference phase ( R=√(x
does not oscillate.
The R[dBm] display on CH1 should read within a
few dB of 0 dBm (0.224 Vrms) depending upon the
amplitude setting of the signal generator.
The R[dBm] display should drop by 6 dBm.
The Display key cycles through the available
choices.
θ
. CH2 now shows the signal phase
changing linearly with a rate equal to the frequency
difference between the signal generator and the
SR844. The readout and bargraph ramp linearly and
smoothly from –180
each period. When displaying
CH2 display is scaled from -180
+180
Switch the SR844 to External Reference Mode.
Since there is no external reference input connected
yet, the Reference Display should read about
19 kHz (the internal oscillator pulls to its lowest
frequency) and the red OUT OF RANGE and
UNLOCK indicators should be lit.
2 2
+y ) ). The reading of R
°
to +180
°
(extreme right).
θ
. The phase is
°
(or vice-versa) once
θ
, the bargraph on the
°
(extreme left) to