SRS Labs SR850 - Manual (Page 108)

4-26
REAR PANEL BNC CONNECTORS
AUX IN 1-4 (A/D Inputs)
These are auxiliary analog inputs which can be
digitized by the SR850. The range is -10V to +10V
and the resolution is 16 bits (1/3 mV). The input
impedance is 1 MΩ.
These inputs may be displayed and stored as
traces on the displays. The inputs are sampled at
the scan sample rate, which may be as fast as
512 Hz. These inputs allow signals other than the
lock-in outputs to be acquired and stored.
Furthermore, complex quantities such as X/Aux1
(ratio) may be acquired and stored directly as
trace quantities.
AUX OUT 1-4 (D/A Outputs)
These are auxiliary analog outputs. The range is
-10V to +10V and the resolution is 1 mV. The
output impedance is <1Ω and the output current is
limited to 10 mA.
These outputs may be programmed from the front
panel or via the computer interfaces. They may be
set to fixed voltages or they may be programmed
to sweep between two voltages. Sweeps may be
either linear or logarithmic. When sweeping, the
outputs change at the sample rate and the sweep
FUSE
PULL
AUX OUT AUX IN
1
2
3
4 4
3
2
1
X Y
TTL OUT
IEEE-488 STD PORT
PC KEYBOARD (8088)
PRINTER PORT
RS232 (DCE)
Fuse : 1A @100/120V & 1/2A @ 220/240V
TRIG IN
MONITOR OUT
PREAMP
STANFORD RESEARCH SYSTEMS - MADE IN U.S.A.
WARNING!:
NO USER SERVICEABLE PARTS INSIDE.
REFER TO USER MANUAL FOR SAFETY NOTICE.
FOR USE BY QUALIFIED PERSONNEL ONLY.
time is the scan length. Output voltage sweeps are
coordinated with the data acquisition. Sweeps
start and stop with the [START/CONT] and
[PAUSE/RESET] keys. Pausing data acquisition
will pause an Aux Out sweep. Resetting the data
buffer will reset a sweeping Aux Out to its starting
value.
X and Y
The X and Y lock-in outputs are always available
at these connectors. The bandwidth of these out-
puts is 100 kHz. A full scale input signal will gener-
ate ±10V at these outputs. The output impedance
is <1Ω and the output current is limited to 10 mA.
These outputs are affected by the X and Y offsets
and expands. The actual outputs are
X Output = (X/sensitivity - offset)xExpandx10V
Y Output = (Y/sensitivity - offset)xExpandx10V
where the offset is a percentage of full scale and
the expand is an integer from 1 to 256. The offsets
and expand are set in the OUTPUT/OFFSET
menu.
MONITOR OUT
This BNC provides a buffered output from the
signal amplifiers and prefilters. This is the signal
just before the A/D converter and PSD. The output
impedance is <1Ω and the output current is limited
to 10 mA.
The gain from the signal input to the monitor
output is the overall gain minus the dynamic
reserve minus 3dB. The overall gain is specified in
dB in the Sensivitiy menu box (in the Gain menu).
The actual dynamic reserve is shown in the moni-
tor settings display. For example, if the sensitivity
is 10 mV, the gain is 60dB. If the dynamic reserve
is 21dB, then the gain from the input to the monitor
output is 60-21-3=36dB or a gain of 63. A 10 mV
(rms) input will result in a .63 Vrms or.9 Vpk
output. The gain is only accurate to about 1.5dB or
20%.
This output is useful for determining the cause of
input overloads and the effects of prefiltering.
However, because the analog gain never exceeds
2000, very small signals may not be amplified
enough to viewed at the monitor output.
Rear Panel