RKI Instruments GX-3R User Manual

GX-3R Operator’s Manual Chapter 2: Description • 13
The standard calibration for the combustible gas sensor is to methane but the sensor will still
detect and respond to a variety of combustible gases.
O
2
/CO/H
2
S Sensors
The O
2
, CO, and H
2
S sensors are electrochemical cells that consist of two precious metal
electrodes in a dilute 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 GX-3R’s circuitry amplifies the
current, converts the current to a gas concentration, and displays the concentration on the
LCD.
There are 4 different types of CO and H
2
S sensors available:
• CO only (ESR-A13P-CO): A single electrochemical cell that detects CO. Instruments
with this sensor cannot detect H
2
S.
•H
2
compensated CO (ESR-A1CP-CO-H): A single electrochemical cell that detects CO.
This sensor does not respond to or responds minimally to hydrogen (displays H2 RICH
once H
2
concentration reaches 2000 ppm). Instruments with this sensor cannot detect H
2
S.
•H
2
S only (ESR-A13i-H2S): A single electrochemical cell that detects H
2
S. Instruments
with this sensor cannot detect CO.
•CO/H
2
S (ESR-A1DR-COHS): A combination electrochemical cell that detects both CO
and H
2
S.
Dummy Sensors
A dummy sensor is installed in any units that have less than 3 sensors. Dummy sensors are
factory installed. The flat side of the dummy sensor faces away from the GX-3R and the
hollow side faces toward the GX-3R.
Filters
Combustible Gas Sensor H
2
S Removal Filter Disk (Dark Red)
An H
2
S removal filter disk is placed into a recess in the filter gasket over the combustible gas
sensor. The filter disk prolongs the life of the combustible gas sensor by preventing H
2
S in the
ambient air from reaching the sensor. The H
2
S filter disk is dark red in color and although it
may darken over time, its color is not indicative of remaining filter life.
The H
2
S filter disk needs replacing once it’s been exposed to 33 ppm hours of H
2
S. This
means the filter needs replacing after 80 minutes of exposure to 25 ppm H
2
S which equates to
40 2-minute calibrations with a cylinder containing 25 ppm H
2
S. If H
2
S exists in the
monitoring environment, the H
2
S filter disk will have to be replaced more frequently.
CO/H
2
S Sensor Dual Filter (Black and White)
A dual filter is placed into a recess in the filter gasket over the dual CO/H
2
S sensor. The black
half is a charcoal filter for the CO sensor. The white half is a humidity filter for the H
2
S
sensor.
Replace the filter if you notice:
• Unexplained CO readings.
• For users with a 1 ppm H
2
S alarm setpoint: A drift on the H
2
S zero reading,
unexplained H
2
S readings, the filter appears dirty, or every 6 months (whichever is
sooner).

RKI Instruments GX-3R Specifications

General

Brand	RKI Instruments
Model	GX-3R
Category	Measuring Instruments
Language	English