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Dynamic Reserve Sensitivity Range
LOW 1 µV through 500 mV
NORM 100 nV through 50 mV
HIGH 100 nV through 5 mV
Dynamic Reserve
The dynamic reserve (DR) is set using the keys in
the DYNAMIC RESERVE section. The reserve is
displayed by the three indicator LED's, HIGH,
NORM, LOW. Only those dynamic reserve
settings available for the sensitivity are allowed
(see above table). For example, when the
sensitivity is 500 mV, the DR will always be LOW.
The dynamic reserve and output stability of each
setting are shown below.
Setting Dynamic Reserve
Output Stability
(ppm/°C)
LOW 20 dB 5
NORM 40 dB 50
HIGH 60 dB 500
Since a higher DR results in degraded output
stability, you should use the lowest DR setting for
which there is no overload indication. Note that
using the Bandpass Filter provides about 20dB of
additional DR and so allows you to operate with a
lower DR setting.
Status
There are five STATUS LED's.
OVLD indicates a signal overload. This condition
can occur when the signal is too large, the
sensitivity is too high, the dynamic reserve is too
low, the offset is on, the expand is on, the time
constant is not large enough, or the ENBW is too
large.
The OVLD LED blinks four times a second when
an output is overloaded. This occurs if an output
exceeds full scale. For example, during a
quadrature measurement where X exceeds full
scale while Y is near zero, a blinking OVLD
indicates that it is safe to take data from the Y
output since only the X output is overloaded. The
signal path to the Y output is not overloaded.
OVLD also blinks if a noise measurement is
attempted on an output which exceeds full scale.
If the OVLD LED is on continuously or flashes
randomly, then an overload has occurred before
the output, i.e. in the ac amplifier or output time
constant. In this case, the dynamic reserve,
sensitivity, time constant, or ENBW needs to be
adjusted.
UNLK indicates that the reference oscillator is not
phase locked to the external reference input. This
can occur if the reference amplitude is too low, the
frequency is out of range, or the trigger mode is
incorrect for the reference signal waveform.
ERR flashes when an error occurs on one of the
computer interfaces, such as an incorrect
command, invalid parameter, etc.
ACT indicates activity on the computer interfaces.
This LED blinks every time a character is received
or transmitted by the SR530.
REM indicates that the unit is in the remote state
and that the front panel controls are not operative.
There are two remote states. The Remote-With-
Lockout will not allow any inputs from the front
panel. The Remote-Without-Lockout command
allows you to return the front panel to operation by
pressing the LOCAL key.
Display Select
The keys in the DISPLAY section select the
parameters to be displayed on the OUTPUT
METERS and the output of the two OUTPUT BNC
connectors. The displayed parameters are
indicated by one of the six DISPLAY LED's and
can be either the two demodulator outputs (X Y),
the demodulator output offsets (X OFST Y OFST),
the magnitude and phase (R Ø), the magnitude
offset and phase (R OFST Ø), the rms noise on X
and Y (X NOISE Y NOISE), or the D/A outputs (X5
D/A X6). When displaying NOISE, the equivalent
noise bandwidth is selected in the TIME
CONSTANT section. When displaying D/A, the 2
outputs are the X5 and X6 rear panel D/A outputs,
allowing the D/A outputs to be set from the front
panel. This feature can be used to set the
reference frequency when using the internal
oscillator.
Channel 1 Display
The channel 1 outputs are summarized below. X
is equal to RcosØ where Ø is the phase shift of
the signal relative to the reference oscillator of the
lock-in.