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98
Operation
This output is useful for determining the cause of input overloads, not necessarily for
viewing the signal of interest. If the f
not be amplified enough to be viewed at the monitor output.
Trig Input
This TTL input is used to start data capture to the internal buffer. This buffer is only
accessible via the computer interface. The remote interface sets the capture start mode to
triggered. The Trig Input then starts data capture into the data buffer. The internal buffer
is 32 MB and can be configured to record (X), (X and Y), (R and θ), or (X, Y, R and θ) at
various sample rates up to 1.25 MHz.
See the Remote Programming section for more information.
Sync/BlazeX Output
This output can be either the reference Sync output or the BlazeX output as configured in
the system menu (hold the [Calc/system] key).
Sync
The Sync output is a ±2V or a 0-2V square wave whose edges are linked to the sine
output zero crossings. This is useful when the sine output amplitude is small and a
synchronous trigger is required (to a scope for example). This output is active even when
the SR865A is locked to an external reference.
BlazeX
The BlazeX output is a ±2V, low latency version of the X output. It's intended for
experiments that require the fastest possible output response, such as feedback loops that
employ the SR865A within the loop. The BlazeX output is always an RC filter (1 to 4
poles) regardless of the front panel Advanced Filter setting, and its maximum time
constant is 10 ms. If a longer time constant is required, the normal X output should be
used instead.
The BlazeX output is modified by offset and expand, but is not affected by the ratio
function.
Preamp Connector
This 9 pin connector provides power to external preamplifiers such as the SR550, SR551,
or SR552. The power connections are described below.
Using SRS Preamps
When using an SRS preamp, connect the power cable (standard male-to-male 9 pin D
connectors) from the preamp to the rear panel preamp connector on the SR865A. Use
SR865A DSP Lock-in Amplifier
Pin
Voltage
1
+18.5 V
2
+5 V
6
−18.5 V
7
Signal Ground
8
Ground
signal is small relative to the input range, it may
ref
(up to 100 mA)
(up to 100 mA)
(up to 100 mA)
Chapter 3
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