RKI Instruments 01 Series Manual - Manual (Page 12)

7 • Description 01 Series Operator’s Manual
noticed, especially in the presence of H
2
S, change the charcoal filter disk
(see the Maintenance section for instructions).
Sensor Retainer
The sensor retainer holds the sensor in place. It is attached to the top of the
case by two Phillips screws. The sensor retainer also covers the buzzer.
Should the sensor require replacement, refer to the Maintenance section
for sensor replacement instructions. The buzzer, however, is not field
replaceable.
The sensor retainer has a single diffusion port through which ambient air
reaches the sensor. Recessed areas in the sensor retainer accept the
charcoal filter disks (CO-01 only) and the sensor cover. The membrane
retainer is installed to the top of the sensor retainer with a single Phillips
screw.
Sensor
The 01 Series uses either an oxygen, CO, or H
2
S sensor. The sensor is
protected by the white sensor cover which is held in place by the
membrane retainer. The sensor cover allows ambient air to diffuse past it to
the sensor. The three sensors used in the three 01 Series models use
different detection principles as described below.
Oxygen Sensor
The oxygen sensor is a galvanic type of sensor. A membrane covers the
cell and allows gas to diffuse into the cell at a rate proportional to the partial
pressure of oxygen. The oxygen reacts in the cell and produces a voltage
proportional to the concentration of oxygen. The voltage is measured by
the 01 Series’ circuitry, converted to a measurement of gas concentration,
and displayed on the LCD.
CO and H
2
S Sensors
The CO and H
2
S sensors are electrochemical sensors that consist of two
precious metal electrodes in an acid electrolyte. A gas permeable
membrane covers the sensor face and allows gas to diffuse into the
electrolyte. The gas reacts in the sensor and produces a current
proportional to the concentration of the target gas. The current is amplified
by the 01 Series’ circuitry, converted to a measurement of gas
concentration, and displayed on the LCD.
LCD
The LCD is visible through the front of the case. When the 01 Series is in
Measuring Mode, the target gas concentration, battery condition, and
alarm indications are displayed on the LCD. Various other items are
displayed when the LCD is in other modes, such as Calibration Mode.