SRS Labs SR640 Series, Manual

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8
Instrument Overview
each other and to the filter ground. The filter
ground is NOT connected to the unit's chassis
ground.
Filter ground for each channel is available at a
rear panel BNC connector.
With this connector,
the user can connect filter ground to chassis
ground or to any other desired point.
COUPLING AND INVER T
The COUPLING button selects either AC or DC in-
put coupling for both the 'A' and 'B' input connec-
tors.
The AC coupling has a nominal -3dB point
of 0.1Hz. Selecting INVERT on the front panel
simply inverts the sign of the output signal with re-
spect to the input.
INPUT AND OUTPUT GAIN
The input and output gain indicators display the
amount of gain present before and after the fil-
ter.
Changing the gain is accomplished with the
up and down buttons to the right of the respective
indicators.
The gain can be changed in 10 dB in-
crements up to a maximum of 60 dB of input gain
(prefilter) and 20 dB of output gain (postfilter).
FILTER IN/OUT
Selecting filter IN on the front panel puts the filter
in the signal path. Selecting filter OUT leaves the
input and output amplifiers in the signal path but
bypasses the filter.
The -3dB point for the input
and output amplifiers with the filter bypassed is ap-
proximately 450 kHz.
OFFSET ADJUST
The front panel offset adjust allows the user to dial
in approximately ±150 mV of input offset volt-
age.
Note that this is a true input offset and the
actual output offset voltage will depend on the se-
lected gain.
CLR /LOCAL
The CLR/LOCAL button has two functions. If the
displayed frequency for either filter channel has
been changed, pressing the CLR/LOCAL button
resets the display to the actual filter frequency.
If
the SR640 has been placed in the REMOTE mode
by a command from the computer interface, press-
ing the CLR/LOCAL button will return the unit to
the LOCAL mode and enable front panel con-
trol.
Note that the CLR/LOCAL button will not re-
turn the unit to local operation if the unit has been
placed in the LOCAL LOCKOUT mode.
STOR E AND R ECALL
The SR640 can store and recall up to 9 complete
instrument setups. To store the current instrument
configuration, press the STORE button.
The set-
up number (1-9) will appear in the channel 2 fre-
quency display. To change the setup number, use
the channel 2 frequency up and down but-
tons.
When the setup number is correct, press
the channel 2 ENTER button to store the set-
up.
Recalling previously stored setups is done in
the same manner. Recalling setup '0' places the
instrument in its default configuration.
Pressing
the CLR/LOCAL button while storing or recalling a
setup aborts the operation and returns the display
to its normal mode.
If an attempt is made to re-
call a setup which has not been previously stored,
the display will indicate an error. In this case, the
CLR/LOCAL button should be pressed to resume
normal operation.
ER ROR, ACTIVITY, and R EMOTE LEDs
The ACT LED lights to indicate any activity over
the interface, such as the receipt of a command.
The ERROR LED will light when a bad command
is received over the computer interface. The
REMOTE LED lights to indicate the SR640 is ei-
ther in the REMOTE or LOCAL LOCKOUT mode
of operation.
In either of these modes, the front
panel buttons are not operational. Only in the
REMOTE mode can front panel operation be re-
gained by pressing the CLR/LOCAL button.
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