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Chapter 1
The Basic Lock-in
This measurement is designed to use the internal oscillator to explore some of the basic lock-in functions.
Specifically, you will measure the amplitude of the Sine Out at various frequencies, amplitudes, time
constants and phase shifts.
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.
2.
Connect the Sine Out + on the front panel to the
A input using a BNC cable.
3.
Touch {Ampl} in the info bar along the top of
the screen. Then {5}{0}{0}{mV}.
4.
Press the [Auto Phase] key.
Do This
Getting Started
Explanation
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.
The lock-in defaults to the internal oscillator
reference set at 100.000 kHz. The reference
source is indicated by the
mode, the lock-in generates a synchronous sine
output at the internal reference frequency.
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.
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 output (Sine+) − (Sine−). In this
case, each BNC has an amplitude of 250 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 500 mV.
Since the phase shift of the sine output is very
close to zero, X (green) should read about
0.5000 and Y (blue) should read close to
0.0000 V.
Automatically adjust the reference phase shift
to eliminate any residual phase error. This
should set the values of Y and θ to zero.
SR865A DSP Lock-in Amplifier
9
Internal
LED. In this
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