Stanford Research Systems SR830 Manual page 15

The Basic Lock-in
Use the knob to adjust the phase shift until Y
is zero and X is equal to the positive
amplitude.
Press [Auto Phase]
6. Press [Freq]
Use the knob to adjust the frequency to
10 kHz.
Use the knob to adjust the frequency back to
1 kHz.
7. Press [Ampl]
Use the knob to adjust the amplitude to
0.01 V.
8. Press [Auto Gain]
9. Press [Sensitivity Up] to select 50 mV full
scale.
Change the sensitivity back to 20 mV.
10. Press [Time Constant Down] to change the
time constant to 300 µs.
Press [Time Constant Up] to change the time
constant to 3 ms.
The knob is used to adjust parameters which are
shown in the Reference display, such as phase,
amplitude and frequency. The final phase value
should be close to zero again.
Use the Auto Phase function to return Y to zero
and X to the amplitude.
Show the internal oscillator frequency in the
Reference display.
The knob now adjusts the frequency. The meas-
ured signal amplitude should stay within 1% of 1 V
and the phase shift should stay close to zero (the
value of Y should stay close to zero).
The internal oscillator is crystal synthesized with
25 ppm of frequency error. The frequency can be
set with 4 1/2 digit or 0.1 mHz resolution, whichev-
er is greater.
Show the sine output amplitude in the Reference
display.
As the amplitude is changed, the measured value
of X should equal the sine output amplitude. The
sine amplitude can be set from 4 mV to 5 V rms
into high impedance (half the amplitude into a 50
Ω load).
The Auto Gain function will adjust the sensitivity so
that the measured magnitude (R) is a sizable per-
centage of full scale. Watch the sensitivity indica-
tors change.
Parameters which have many options, such as
sensitivity and time constant, are changed with up
and down keys. The sensitivity and time constant
are indicated by leds.
The values of X and Y become noisy. This is
because the 2f component of the output (at 2 kHz)
is no longer attenuated completely by the low pass
filters.
Let's leave the time constant short and change the
filter slope.
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