Advanced Measurement Technology 273A, User Manual

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Chapter 2—Safety Considerations 7
Warning! Potentials as high as 100 V capable of delivering currents as high as 1 A may be
present at the cell connections. To avoid the possibility of dangerous electrical
shock, always have the cell disabled when working with the cell connections. The
cell status is determined by the two keys in the cell area of the Model 273A front
panel. These keys function as follows.
Warning! Anytime work at the cell is done, including making and breaking connections, this
switch absolutely should be in the off position. The 100 V output and high current
capability of the 273A make it a dangerous device, one capable of causing severe
injury or even death.
Table 1. Voltage-Selection Card Position as a
Function of Line Voltage
SELECTOR CARD OPERATING
NUMBER EXPOSED VOLTAGE RANGE
100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90-110V
120 . . . . . . . . . . . . . . . . . . . . . . . . . . . 110-L30 V
220 . . . . . . . . . . . . . . . . . . . . . . . . . . 210-230 V
240 . . . . . . . . . . . . . . . . . . . . . . . . . . . 230-260 V
Next, check the fuse rating. For operation from a line voltage in either of the two lower ranges,
use a slow-blow fuse rated at 4A (voltage rating 125 V or higher). For operation from a line
voltage in either of the two higher ranges, use a slow-blow fuse rated at 2 A (voltage rating of
250 V or higher). When the proper fuse has been installed, slide the plastic door back over the
fuse compartment so that the power cord can be reconnected.
Make sure that only fuses with the required current rating and of the speed type are used for
replacement. The use of makeshift fuses and the short-circuiting of fuse holders are dangerous.
2.4. Cell Cable
There are two keys and one indicator in this group. All three are associated with the internal relay
that provides the connection to the counter electrode at the cell. The CELL ENABLE key has two
positions, in (ON) and out (OFF). CELL ENABLE is a hard-wired fail-safe switch. Whenever it is
in the OFF position, there is no possible way, including commands from an external computer,
for voltage to be applied to the counter electrode. This switch is provided to assure operator
safety when working on the cell.
The upper Cell key provides the normal Cell ON/OFF control during operation. Unlike the CELL
ENABLE switch, this key is subject to software override. For example, the ON state must be
selected before starting a scan. However, a scan may contain delay intervals to be carried out in
the Cell OFF state. If this is the case, the cell is turned off automatically at the appropriate points
in the scan sequence.
The cell status can be noted at any time by observing the Cell indicator. This indicator is unique,
first in that it is red and second in that it has three states, OFF, HALF BRIGHT, and FULL
BRIGHT. The significance of each state is:
OFF: Both the CELL key and the CELL ENABLE switch are OFF, OR the CELL key is OFF and
the CELL ENABLE switch is ON.
HALF BRIGHT: The CELL key is ON but the CELL ENABLE switch is OFF.
FULL BRIGHT: Both the CELL key and the CELL ENABLE switch are ON. The cell is ON only
when the light is at full brightness.