Stanford Research Systems SR865A, Operation Manual

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20 Getting Started Chapter 1
SR865A DSP Lock-in Amplifier
Sensitivity, Offset and Expand
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.
Do This Explanation
1. Disconnect all cables from the lock-in. Turn the
power on while holding down the [Local] key.
The power switch is on the power entry module
on the rear panel. When the power is turned on with [Local]
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.
2. Connect the Sine Out + on the front panel to the
A input using a BNC cable. The lock-in defaults to the internal oscillator
reference set at 100.000 kHz.
The default data screen is the Trend Graph. The
4 displayed parameters default to X, Y, R and θ.
Each parameter has a numeric display, a bar
graph and a trend graph. The trend graph is a
continuously autoscaling graph of the recent
history of each parameter. This data screen has
no adjustments available.
The default sine amplitude is 0 Vrms. Thus the
data displays will read 0 for X, Y and R. θ will
be just noise.
3. Touch {Ampl} in the info bar along the top of
the screen. Then {1}{0}{0}{mV}. The lock-in parameters shown in the info bar at
the top of the screen may be entered using a
numeric keypad simply by touching them.
The Sine Out amplitude is specified for
differential o
utput (Sine+) − (Sine−). In this
case, each BNC has an amplitude of 50 mV
(rms) with a 50Ω output. The lock
-in input is
high impedance so the output of each BNC is
doubled and the lock-in measures 100 mV.
Since the phase shift of the sine output is very
close to zero, X (green) should read about
0.1000 and Y (blue) should read close to
0.0000 V.