Stanford Research Systems SR865A Operation Manual page 115

Chapter 3
Timebase In/Out
Apply a 10 MHz sine signal (1 Vrms) to the TIMEBASE input to lock the SR865A's
timebase to an external timebase. The internal reference frequency of the SR865A is
derived from this timebase. When multiple SR865A's are locked to the same 10 MHz
timebase, then harmonically related internal frequencies on different units will stay in
phase indefinitely.
The Ext 10 MHz
The SR865A also outputs its own 10 MHz timebase (to another unit).
Note that external function generators, even a direct digital synthesizer locked to the
same 10 MHz timebase, will not stay in phase with the SR865A. This is because the
resolution of the frequency tuning word in the external direct digital synthesizer differs
from the SR865A.
HDMI Output
Use the HDMI output to display the SR865A screen on a large computer monitor or
television. The output has a resolution of 640×480 and a frame rate of 60 Hz.
Aux In 1–4
These are auxiliary analog inputs which can be digitized by the SR865A. The range is
±10.5 V, the resolution is 1 mV and the inputs are 1 MΩ. These inputs can be displayed
on the screen, read over the computer interfaces and graphed on the strip charts.
Aux Out 1–4
These are auxiliary analog outputs. The range is ±10.5 V and the resolution is 1 mV.
These outputs may be programmed from the front panel (via [Aux Output]), scanned (via
[Scan/setup]) or controlled via the computer interfaces. Aux Out 4 is used to control an
SR540 chopper when the reference mode is Chop.
X and Y Outputs
The X and Y lock-in outputs are always available at these connectors. Although the
demodulator output values are generated at a (time constant dependent) rate up to
1.25 MHz, the X and Y output hardware is always upsampled to an output update rate of
2.222 MHz. An input signal equal to the sensitivity will generate ±10 V at these outputs.
These outputs are identical to the front panel CH1 and CH2 outputs when set to X and Y.
These outputs are affected by the sensitivity and the X and Y offsets and expands.
Signal Monitor Output
This BNC provides a buffered output from the signal amplifier. This is the signal just
before the anti-aliasing filter, A/D converter and PSD. The amplifier gain is determined
by the Input Range (voltage input) or the Current Range (current input). The output is
about 1 V for a maximum input.
LED is on when the unit is locked to an external timebase.
Operation
SR865A DSP Lock-in Amplifier
97