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DISPLAYS and TRACES
This measurement is designed to use the internal oscillator and an external signal source to explore some of
the display types. You will need a synthesized function generator capable of providing a 100 mVrms sine
wave at 1.000 kHz (the DS345 from SRS will suffice), BNC cables and a terminator appropriate for the gener-
ator function output.
Specifically, you will display the lock-in outputs when measuring a signal close to, but not equal to, the inter-
nal reference frequency. This setup ensures changing outputs which are more illustrative than steady outputs.
The displays will be configured to show X, Y, R and θ in bar graph and polar formats. The example Scans and
Sweeps demonstrates the use of the chart graph.
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. Turn on the function generator, set the fre-
quency to 1.0000 kHz (exactly) and the ampli-
tude to 500 mVrms.
Connect the function output (sine wave) from
the synthesized function generator to the A
input using a BNC cable and appropriate
terminator.
3. 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 (Rcosθ) and
the lower graph shows the the value of Y (Rsinθ).
The input impedance of the lock-in is 10 MΩ. The
generator may require a terminator. Many genera-
tors have either a 50Ω or 600Ω output impedance.
Use the appropriate feedthrough or T termination if
necessary. In general, not using a terminator
means that the function output amplitude will not
agree with the generator setting.
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 internal oscillator sets
the detection frequency.
The internal oscillator is crystal synthesized so
that the actual reference frequency should be very
close to the actual generator frequency. The X and
Y displays should read values which change very
slowly. The lock-in and the generator are not
phase locked but they are at the same frequency
with some slowly changing phase.
Display the Reference and Phase menu.
Displays and Traces