Stanford Research Systems SR830, Manual

Page: 18 / 177

2-7
X, Y, R and
θ
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 DS335 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
.
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. 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 [Freq]
Use the knob to change the frequency to
999.8 Hz.
When the power is turned on with the [Setup] key
pressed, the lock-in returns to its standard set-
tings. See the Standard Settings list in the
Operation section for a complete listing of the
settings.
The Channel 1 display shows X and Channel 2
shows Y.
The input impedance of the lock-in is 10 M
Ω
. The
generator may require a terminator. Many genera-
tors have either a 50
Ω
or 600
Ω
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 is indi-
cated by the INTERNAL led. 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.
Show the internal oscillator frequency on the
Reference display.
By setting the lock-in reference 0.2 Hz away from
the signal frequency, the X and Y outputs are
0.2 Hz sine waves (frequency difference between
reference and signal). The X and Y output displays
X, Y, R and
θ