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A current limiting resistor (R1 and R2) is potted into the end of each battery. This assures that
under no circumstances can more than 25 milliamperes (100 milliwatts) be switched or drawn
from either battery supply. This means that the Model 311XL may be used in explosive
atmospheres where arcs of 100 milliwatts or less can be tolerated.
This safety feature does not apply when the instrument is being charged (AC power cord
connected and selector switch in the “OFF” position). The instrument should not be used in
explosive atmospheres when the batteries are being charged.
To determine the state of the rechargeable batteries turn the range selector knob
counterclockwise to the battery test position and hold there (spring loaded switch). Observe that
the meter indicator stays within the battery limits, *if not, recharge of the batteries is in order).
Release Range Selector Switch, it will automatically return to the OFF position.
1.3.4 Accuracy and Response. Accuracy at 25
o
C and constant pressure after
thermal equilibrium has been reached. Basic accuracy: +/- 2% of full scale for all ranges except
0-2 PPM range. Accuracy for 0-2 PPM range: +/- 5% of full scale.
Accuracy over the temperature range 0-35
o
C at constant pressure after thermal equilibrium has
been reached. Basic accuracy: +/- 5% of scale for all ranges except 0-2 PPM range. Accuracy for
0-2PPM range, +/- 10% of full scale.
If the instrument is moved from one ambient temperature to another of 10
o
C or higher
differential, the instrument should be allowed to equilibrate for 3-4 hours before being used.
The readings obtained during the transition time may be in error greater than the specifications.
Response time: 90% in 90 sec. on the 0-2 PPM range with a flow rate of 2.5 SCFH.
1.3.5 Compact Packaging. The instrument is housed in a 6-1/8” X 9-1/2” X 5-
5/8” aluminum case that is equipped with a carrying handle and foot pads. When in use, the
analyzer should be placed in an upright position on a level surface (off level positioning will
detract from meter accuracy).
Access to the instrument interior is gained by loosening (ccw) the three (3) 1/4 turn screw driver
type fasteners on the back of the outer case. The case may then be detached from the driver type
fasteners on the back of the outer case. The case may then be detached from the control panel
assembly. Further disassembly may be accomplished by removing the back plate assembly from
its four (4) mounting standoffs and laying the two separated assemblies out as illustrated on the
“Analyzer Wiring Diagram”. The diagram is included among the drawings at the rear of the
manual.
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