RKI Instruments HS-94 - Manual (Page 4)

Oxygen Sensor
The oxygen sensor is an electrochemical cell, consisting of gold and lead electrodes
in an alkaline electrolyte. A fluorocarbon membrane covers the cell, and allows
atmosphere to diffuse into the electrolyte at a rate proportional to the partial
pressure of oxygen. The oxygen reacts in the cell, producing a current proportional
to the concentration of oxygen. The current develops a voltage across a
temperature-compensating thermistor/resistor network. The voltage is measured
by the circuitry of the GX-82 and converted to a measurement of gas concentration.
CO & H
2
S Sensors
The CO and H
2
S sensors are electrochemical cells, consisting of three precious metal
electrodes in an acid electrolyte. A gas permeable membrane covers the cell, and
allows gas in the atmosphere to diffuse into the electrolyte at a rate proportional to
its partial pressure. The gas reacts in the cell, producing a current proportional to the
concentration of gas. The current is amplified by the circuitry of the 94 series
instrument and converted to a measurement of gas concentration.
CONTROL PANEL
The control panel is on the side of the instrument for easy access when the display is
viewed. It contains the display and switches that control the many functions of the
instrument. The switches are touch-pads, to reduce the possibility of accidental
activation or damage.
• POWER / MODE Button
The POWER / MODE switch controls power to the instrument, and is also
used for selecting the mode of operation of the unit.
• AIR Button
The AIR switch is used for adjusting the unit in fresh air, and is also used in
conjunction with the POWER / MODE switch for accessing various other
functions which will be explained later in this manual.
BATTERY COMPARTMENT
The 94 series battery compartment is located on the rear of the instrument. The sliding
access panel allows for easy replacement of the batteries. A large screw on the side of
the unit holds the battery compartment cover in place. The screw can be removed with
a screwdriver, fingernail, or coin.
The 94 series uses two “AAA” size cells standard alkaline batteries which will run the
unit for approximately 100 hours.
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