The Basic Lock-In - Stanford Research Systems SR810 Manual

The Basic Lock-in

THE BASIC LOCK-IN
This measurement is designed to use the internal oscillator to explore some of the basic lock-in functions.
You will need BNC cables.
Specifically, you will measure the amplitude of the Sine Out at various frequencies, sensitivities, time
constants and phase shifts.
1. Disconnect all cables from the lock-in. Turn
the power on while holding down the [Setup]
key. Wait until the power-on tests are
completed.
2. Connect the Sine Out on the front panel to
the A input using a BNC cable.
3. Press [Phase]
Press the [+90°] key.
Use the knob to adjust the phase shift.
Leave the phase shift at a non-zero value.
Press [Auto Phase]
4. Press [Freq]
Use the knob to adjust the frequency to
10 kHz.
When the power is turned on with the [Setup] key
pressed, the lock-in returns to its standard default
settings. See the Standard Settings list in the
Operation section for a complete listing of the settings.
The Channel 1 display shows X.
The lock-in defaults to the internal oscillator reference
set at 1.000 kHz. The reference mode is indicated by
the INTERNAL led. In this mode, the lock-in generates
a synchronous sine output at the internal reference
frequency.
The input impedance of the lock-in is 10 MΩ. The Sine
Out has an output impedance of 50 Ω. Since the Sine
Output amplitude is specified into a high impedance
load, the output impedance does not affect the
amplitude.
The sine amplitude is 1.000 Vrms and the
sensitivity is 1 V(rms). Since the phase shift of the sine
output is very close to zero, Channel 1 (X) should read
close to 1.000 V.
Display the reference phase shift in the Reference
display. The phase shift is zero.
This adds 90° to the reference phase shift. The value
of X drops to zero (out of phase).
The knob is used to adjust parameters which are
shown in the Reference display, such as phase,
amplitude and frequency.
Use the Auto Phase function to automatically adjust the
phase to make X a maximum (and Y a minimum). The
phase should be set very close to zero.
Show the internal oscillator frequency in the Reference
display.
The knob now adjusts the frequency. The measured
signal amplitude should stay within 1% of 1 V.
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