SRS Labs SR850 - Manual (Page 15)

2-3
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 con-
stants and phase shifts. The "normal" lock-in display will be used throughout this exercise.
1. Disconnect all cables from the lock-in. Turn
the power on while holding down the [
←
]
(backspace) 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 [AUTO PHASE]
4. Press [REF/PHASE]
When the power is turned on with the backspace
key depressed, the lock-in returns to its default
settings. See the Default Settings list in the Menu
section for a complete listing of the settings.
The display is the "normal" lock-in display. The
lock-in setup is displayed across the top of the
screen. The sensitivity, reserve, time constant,
prefilters and input configuration are all easily visi-
ble. Watch how these indicators change as you
change parameters. The upper numeric readout
and bar graph shows the value of X (Rcos
θ
) and
the lower graph shows the the value of Y (Rsin
θ
).
The input impedance of the lock-in is 10 M
Ω
. 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 lock-in defaults to the internal oscillator refer-
ence set at 1.000 kHz. The reference mode (Intrnl)
and frequency are displayed at the bottom of the
screen. In this mode, the lock-in generates a syn-
chronous sine output at the internal reference
frequency.
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, the upper display
(X) should read close to 1.000 V and the lower dis-
play (Y) should read close to 0.000 V.
Automatically adjust the reference phase shift to
eliminate any residual phase error. This should set
the value of Y to zero.
Display the Reference and Phase menu. The
phase shift (displayed in the top menu box) should
be close to zero.
The Basic Lock-in