Scanning - Stanford Research Systems SR865A Operation Manual

30 Getting Started

Scanning

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 500 mVrms
sine wave at 100.000 kHz, BNC cables and a terminator appropriate for the generator function output.
Specifically, you will scan the lock-in internal reference frequency through the signal frequency.
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. Turn on the function generator, set the frequency
to 100.000 kHz (exactly) and the amplitude 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 and hold [Scan/setup] to display the scan
menu.
SR865A DSP Lock-in Amplifier
Do This 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 input impedance of the lock-in is 10 MΩ.
The generator may require a terminator. Many
generators 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 internal oscillator should be very close to
the actual generator frequency. The X (green)
and Y (blue) displays should read values which
change slowly. The lock-in and the generator
are not phase locked but they are at the same
frequency with some slowly changing θ
(orange). The signal magnitude R (yellow) is
phase independent and does not change.
Parameters which may be scanned are F
Amplitude, DC Level, Aux Out 1 and 2.
Scans can be linear or logarithmic, repeat,
repeat up and down or run once and pause.
The Scan Duration is the total time to move
from the Begin Value to the End Value. The
Parameter Update Interval is the time spent at
each scan step along the way. The shorter the
update time, the smaller the steps and the
smoother the scan. The longer the update time,
the fewer steps. With experiments that take time
to settle after a parameter change, it can be
beneficial to set the update time long enough to
accommodate the settling.
Chapter 1
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