Outputs, Offsets And Expands - Stanford Research Systems SR830 Manual

OUTPUTS, OFFSETS and EXPANDS

This measurement is designed to use the internal oscillator to explore some of the basic lock-in outputs. You
will need BNC cables and a digital voltmeter (DVM).
Specifically, you will measure the amplitude of the Sine Out and provide analog outputs proportional to the
measurement. The effect of offsets and expands on the displayed values and the analog outputs will be
explored.
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. Connect the CH1 OUTPUT on the front panel
to the DVM. Set the DVM to read DC Volts.
4. Press [Ampl]
Use the knob to adjust the sine amplitude to
0.5 V.
Outputs, Offsets and Expands
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 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
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 50Ω. 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 and Channel 2 (Y)
should read close to 0.000 V.
The CH1 output defaults to X. The output voltage
is simply (X/Sensitivity - Offset)xExpandx10V. In
this case, X = 1.000 V, the sensitivity = 1 V, the
offset is zero percent and the expand is 1. The
output should thus be 10 V or 100% of full scale.
Display the sine output amplitude.
Set the amplitude to 0.5 V. The Channel 1 display
should show X=0.5 V and the CH1 output voltage
should be 5 V on the DVM (1/2 of full scale).
2-9