Specifications

Safety and Preparation for Use
3
SAFETY AND PREPARATION FOR USE
**** CAUTION ****
This instrument may be damaged if operated with
the LINE VOLTAGE SELECTOR set for the
wrong ac line voltage or if the wrong fuse is
installed.
LINE VOLTAGE SELECTION
The SR400 operates from a 100V, 120V, 220V, or
240V nominal ac power source having a line
frequency of 50 or 60 Hz. Before connecting the
power cord to a power source, verify that the
LINE VOLTAGE SELECTOR card, located in the
rear panel fuse holder, is set so that the correct ac
input voltage value is visible.
Conversion to other ac input voltages requires a
change in the fuse holder voltage card position and
fuse value. Disconnect the power cord, open the
fuse holder cover door and rotate the fuse-pull
lever to remove the fuse. Remove the small
printed circuit board and select the operating
voltage by orienting the printed circuit board to
position the desired voltage to be visible when
pushed firmly into its slot. Rotate the fuse-pull
lever back into its normal position and insert the
correct fuse into the fuse holder.
LINE FUSE
Verify that the correct line fuse is installed before
connecting the line cord. For 100V/120V, use a 1
Amp fuse and for 220V/240V, use a 1/2 Amp
fuse.
LINE CORD
The SR400 has a detachable, three-wire power
cord for connection to the power source and to a
protective ground. The exposed metal parts of the
instrument are connected to the outlet ground to
protect against electrical shock. Always use an
outlet which has a properly connected protective
ground.
WARNING REGARDING USE WITH
PHOTOMULTIPLIERS
The signal inputs may be damaged if a
photomultiplier is used improperly with the photon
counter. When left completely unterminated, a
PMT will charge a cable to a few hundred Volts in
a very short time. If this cable is connected to a
signal input, the stored charge may damage the
front-end transistors. To avoid this problem,
provide a leakage path of about 100 KΩ to ground
inside the base of the PMT to prevent charge
accumulation.
CONNECTION TO OTHER INSTRUMENTS
All front panel BNC shields are connected to the
chassis ground and to the power outlet ground via
the power cord. Do not apply any voltage to either
the shields or to the outputs. The outputs are not
protected against connection to any potential other
than ground.