RKI Instruments GX-3R User manual

RKI Instruments, Inc.
www.rkiinstruments.com
GX-3R
Condensed Operator’s Manual
(go to www.rkiinstruments.com/product/gx-3r-gas-detector/ for full manual)
Part Number: 71-0523
Revision: A
Released: 1/17/23

2• GX-3R Condensed Operator’s Manual
WARNING
Read and understand this instruction manual before operating
instrument. Improper use of the gas monitor could result in bodily
harm or death.
Maintenance of the gas monitor is essential for proper operation and
correct readings.
Bump test the instrument before each day’s use with a known
concentration of each target gas. A bump test can be done in User
Mode’s BUMP item or by applying gas in Measuring Mode. The
instrument does not need to be calibrated unless it does not pass the
User Mode bump test or does not respond appropriately, as defined by
the user, in Measuring Mode. For more information about bump test
and calibration requirements, see IEC 60079-29-2.

GX-3R Condensed Operator’s Manual • 3
Table of Contents
Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About the GX-3R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter 2: Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Instrument Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Included Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Other Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Chapter 3: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Turning On the GX-3R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Performing a Demand Zero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Turning Off the GX-3R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Measuring Mode Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Monitoring an Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Combustible Gas Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Oxygen-Enriched Atmospheres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
H2-Compensated CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Interference Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Aspirator Adapter Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Responding to Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Data Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Chapter 4: Display Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Tips for Using Display Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

4• GX-3R Condensed Operator’s Manual
Peak Screen (PEAK). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
STEL Screen (STEL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
TWA Screen (TWA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Combustible Sensor Target Gas Conversion (LIST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Changing the User ID (USER ID) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Changing the Station ID (STN ID) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Last Successful Calibration Date (CAL DATA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Last Successful Bump Test Date (BUMP DATA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Date, Time, and Temperature Screen (TEMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Viewing Alarm Settings Screen (ALARM--PT). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Chapter 5: User Mode and Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Entering User Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Tips for Using User Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Performing a Bump Test (BUMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Performing a Calibration (GAS CAL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Chapter 6: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Instrument Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Recharging the Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Replacing the Buzzer Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Replacing the Sensor Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Replacing the Hydrophobic Dust Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Replacing a Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Replacing the Battery Board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Chapter 7: Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Chapter 8: General Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Appendix A: Maintenance Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

GX-3R Condensed Operator’s Manual • 5
Entering Maintenance Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Tips for Using Maintenance Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Appendix B: Gas Select Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Entering Gas Select Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Tips for Using Gas Select Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Appendix C: Interference Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
ESR-A13i-H2S, H2S Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
ESR-A13P-CO, CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
ESR-A1CP-COH, H2-Compensated CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
ESR-A1DP-COHS, CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
ESR-A1DP-COHS, H2S Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
WARNING: Understand manual before operating. Substitution of components may impair intrinsic
safety. To prevent ignition of a hazardous atmosphere, batteries must only be changed or
charged in an area known to be nonhazardous.

6• Chapter 1: Introduction GX-3R Condensed Operator’s Manual
Chapter 1: Introduction
Overview
This chapter briefly describes the GX-3R gas monitor. This chapter also describes the
GX-3R Operator’s Manual (this document). Table 1 at the end of this chapter lists the specifications for the
GX-3R.
About the GX-3R
Using an advanced detection system consisting of up to three gas sensors, the GX-3R personal four-gas
monitor detects the presence of combustible gas, oxygen (O2), carbon monoxide (CO), and hydrogen
sulfide (H2S) simultaneously. The GX-3R’s compact size and easy-to-use design make it ideally suited for
a wide range of applications, including sewage treatment plants, utility manholes, tunnels, hazardous waste
sites, power stations, petrochemical refineries, mines, paper mills, drilling rigs, and fire fighting stations.
The GX-3R offers a full range of features, including:
• Simultaneous monitoring of one to four gases
• Liquid crystal display (LCD) for complete and understandable information at a glance
• Ultrabright alarm LEDs
• Distinctive audible/vibrating alarms for dangerous gas conditions and audible alarms for unit
malfunction
• Microprocessor control for reliability, ease of use, and advanced capabilities
• Data logging functions
• Alarm trend data
• STEL, TWA, and over range alarms
• Peak readings
• Built-in time function
• Lunch break feature
• CSA “C/US” classified as intrinsically safe (see Table 2 on page 7)
WARNING: The Model GX-3R detects oxygen deficiency, elevated levels of oxygen, combustible
gases, carbon monoxide, and hydrogen sulfide, all of which can be dangerous or life
threatening. When using the GX-3R, you must follow the instructions and warnings in
this manual to assure proper and safe operation of the unit and to minimize the risk of
personal injury. Be sure to maintain and periodically calibrate the GX-3R as described in
this manual.

GX-3R Condensed Operator’s Manual Chapter 1: Introduction • 7
Specifications
Table 1: Standard Sensor Specifications/Alarm Points
Combustible Gas,
Methane (CH4)
Calibration Standard*
Oxygen (O2)Hydrogen
Sulfide (H2S)
Carbon
Monoxide (CO)
Detection Range 0 - 100% LEL 0 - 40% volume 0 - 200.0 ppm 0 - 2000 ppm
Lower Detectable
Limit (LDL)
n/a n/a 0.5 ppm 2 ppm
Reading
Increment
1% LEL 0.1% volume 0.1 ppm 1 ppm
Warning
Setpoint
10% LEL 19.5% volume,
decreasing
5.0 ppm 25 ppm
Alarm
Setpoint
25% LEL 18.0% volume,
decreasing
30.0 ppm 50 ppm
Alarm H
Setpoint
50% LEL 23.5% volume,
increasing
100.0 ppm 1200 ppm
STEL Setpoint n/a n/a 5.0 ppm 200 ppm
TWA Setpoint n/a n/a 1.0 ppm 25 ppm
* The GX-3R is also available set up for general hydrocarbons and calibrated to a combustible gas other than methane,
such as isobutane. Consult RKI Instruments, Inc. for further information.
Table 2: GX-3R Specifications
Sampling Method Diffusion
Response Time T90 within 30 seconds
Display Graphics LCD Display
Environmental
Conditions
• 3000 meter maximum altitude
• Operating pressure: 70 - 120 kPa (70 - 110 kPa for explosion proof)
• Pollution degree 2
•IP66/68
Operating
Temperature &
Humidity
Continuous environment: -20°C to 50°C/Below 90% RH
Temporary environment (up to 15 minutes): -40°C to 60°C/Below 95% RH

8• Chapter 1: Introduction GX-3R Condensed Operator’s Manual
Safety/
Regulatory
• ATEX: Certificate Number: DEKRA 17ATEX0103 X
II1G Ex da ia IIC T4 Ga/IM1 Ex da ia I Ma (with NCR-6309)
II1G Ex ia IIC T4 Ga/IM1 Ex ia I Ma (without NCR-6309)
• IECEx: Certificate Number: IECEx DEK 17.0050X
Ex da ia IIC T4 Ga/Ex da ia I Ma (with NCR-6309)
Ex ia IIC T4 Ga/Ex ia I Ma (without NCR-6309)
• CSA classified, “C/US”, as Intrinsically Safe. Class I Division 1 Groups A, B, C, D T4.
Class I, Zones 0, A/Ex da ia IIC T4 Ga (with NCR-6309)
Class I, Zones 0, A/Ex ia IIC T4 Ga (without NCR-6309)
C US
186718
Power Supply Lithium ion battery pack (3.7 VDC, 200 mA)
Continuous
Operating Hours
@ 25 °C
With combustible gas sensor: 25 hours in Measuring Mode (non-alarm operation)
Without combustible gas sensor: 60 hours in Measuring Mode (non-alarm operation)
Battery
Charger Ratings
Input: 100 - 240 VAC, 47 - 63 Hz, 2.4 A
Output: 5.99 VDC, 2A max
Case High-impact Plastic, RF Shielded, Dust and Weather Proof (IP66/68)
Included
Accessories
• Alligator clip
• Rubber boot
• Wrist strap
• Calibration cup
• Single-unit charger
Other
Accessories
• 12 VDC adapter
• Multi-unit charger
• Belt clip
•SDM-3R
•RP-3R
• Aspirator adapter
• IrDA/USB Cable for connecting to a computer when using the Data Logger Management Program
(not needed if computer has an infrared port)
Dimensions and
Weight
Approximately 65(H) x 58(W) x 26(D) mm (2.6”H x 2.3”W x 1.0”D)
Approximately 100 g (3.5 oz.)
Table 2: GX-3R Specifications

GX-3R Condensed Operator’s Manual Chapter 1: Introduction • 9
About this Manual
The GX-3R Operator’s Manual uses the following conventions for notes, cautions, and warnings.
NOTE: Describes additional or critical information.
CAUTION: Describes potential damage to equipment.
WARNING: Describes potential danger that can result in injury or death.

10 • Chapter 2: Description GX-3R Condensed Operator’s Manual
Chapter 2: Description
Overview
This chapter describes the GX-3R instrument and its accessories.
Instrument Description
Case
The GX-3R’s sturdy, high-impact plastic case is radio frequency (RF) resistant and is suitable for use in
many environmental conditions, indoors and out. The case is dust proof and water resistant. A clear plastic
window on the front of the case allows for LCD viewing. The black bottom cover, located on the bottom of
the case, allows access to the filters and sensors. A sensor retainer and filter gasket help orient and retain
the sensor and filters.
Three threaded inserts on the back of the case allow for installation of an alligator clip or belt clip.
LCD
The digital LCD (liquid crystal display) simultaneously shows the gas reading for all installed sensors. The
LCD also shows information for each of the GX-3R’s operating modes.
WARNING: A thin protective film covers the display to prevent scratches during shipping. Remove
this film before use. Leaving the film installed voids the intrinsically safe certification.
GX-3R
POWER
MODE
CO/H2SLELO2
AIR
Bottom
Cover
Charging
Socket
Sensor
Retainer
Buzzer
Opening Front Back
LCDLEDs
Threaded
Inserts
Figure 1: Component Location

GX-3R Condensed Operator’s Manual Chapter 2: Description • 11
Control Buttons
Two control buttons, AIR and POWER MODE, are located below the LCD.
Alarm LEDs
The six alarm LEDs around the edge of the case alert you to gas, low battery, and failure alarms.
Buzzer
One solid-state electronic buzzer is located inside the case. Sound exits the case through a hole in the
middle front of the case. The buzzer sounds for gas alarms, malfunctions, low battery voltage, and as an
indicator during use of the GX-3R’s many display and adjustment options.
Vibrator
A vibrating motor inside the GX-3R case vibrates for gas alarms, unit malfunctions, and as an indicator
during normal use of the various modes of the GX-3R.
NOTE: If STEALTH is set to ON, the vibrator only functions when VIB in the STEALTH Gas Select
Mode item is set to ON. See page 92.
Sensors
The GX-3R uses three sensors to monitor combustible gas, oxygen (O2), carbon monoxide (CO), and
hydrogen sulfide (H2S) simultaneously. The sensors are located inside the GX-3R and are held in their
sockets by the sensor retainer and bottom cover. The sensors use different detection principles, as
described below.
Table 3: GX-3R Control Button Functions
Button Function(s)
AIR • turns on LCD backlight
• resets alarm condition if LATCHING is set to ON in Maintenance Mode
• enters User Mode, Maintenance Mode, and Gas Select Mode when used with
POWER MODE button
• activates the demand zero function (adjusts the GX-3R’s fresh air reading)
• changes the value of a parameter available for adjustment
• scrolls through parameter options
POWER MODE • turns the GX-3R on and off
• turns on LCD backlight
• enters and scrolls through Display Mode
• enters instructions into the GX-3R’s microprocessor
• resets alarm condition if LATCHING is set to ON in Maintenance Mode
• enters User Mode, Maintenance Mode, and Gas Select Mode when used with AIR
button

12 • Chapter 2: Description GX-3R Condensed Operator’s Manual
Combustible Gas Sensor
The combustible gas sensor detects combustible gas in the % LEL range using 2 catalytic elements: a
standard element and a poison-resistant element that is resistant to sensor poisons like silicone. The
element’s resistance changes based on the reaction of gas with oxygen. The change in resistance affects the
current flowing through the element. The GX-3R’s circuitry amplifies the current, converts the current to a
gas concentration, and displays the concentration on the LCD.
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.
O2/CO/H2S Sensors
The O2, CO, and H2S 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 H2S sensors available:
• CO only (ESR-A13P-CO): A single electrochemical cell that detects CO. Instruments with this
sensor cannot detect H2S.
•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 H2
concentration reaches 2000 ppm). Instruments with this sensor cannot detect H2S.
•H
2S only (ESR-A13i-H2S): A single electrochemical cell that detects H2S. Instruments with this
sensor cannot detect CO.
•CO/H
2S (ESR-A1DR-COHS): A combination electrochemical cell that detects both CO and H2S.
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 H2S Removal Filter Disk (Dark Red)
An H2S 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 H2S in the ambient air from
reaching the sensor. The H2S filter disk is dark red in color and although it may darken over time, its color
is not indicative of remaining filter life.
The H2S filter disk needs replacing once it’s been exposed to 33 ppm hours of H2S. This means the filter
needs replacing after 80 minutes of exposure to 25 ppm H2S which equates to 40 2-minute calibrations
with a cylinder containing 25 ppm H2S. If H2S exists in the monitoring environment, the H2S filter disk
will have to be replaced more frequently.
CO/H2S Sensor Dual Filter (Black and White)
A dual filter is placed into a recess in the filter gasket over the dual CO/H2S sensor. The black half is a
charcoal filter for the CO sensor. The white half is a humidity filter for the H2S sensor.
Replace the filter if you notice:
• Unexplained CO readings.
• For users with a 1 ppm H2S alarm setpoint: A drift on the H2S zero reading, unexplained H2S
readings, the filter appears dirty, or every 6 months (whichever is sooner).

GX-3R Condensed Operator’s Manual Chapter 2: Description • 13
CO Sensor Charcoal Filter (Black)
A black charcoal filter is placed into a recess in the filter gasket over the CO sensor. The charcoal filter
disk scrubs H2S and certain hydrocarbons out of the sample to avoid false CO readings. If false or elevated
CO readings are noticed, especially in the presence of H2S, change the charcoal filter.
H2S Sensor Humidity Filter (White)
A white humidity filter covers the H2S sensor. The filter absorbs humidity in the sampling environment to
prevent unstable readings around 0 ppm H2S. For users with a 1 ppm H2S alarm setpoint, the filter should
be replaced every 6 months, if you notice a drift on the zero reading, or if the filter appears dirty
(whichever is sooner). For users with a 2 ppm or higher H2S setpoint, the filter does not necessarily need to
be replaced.
Hydrophobic Dust Filter
The oval-shaped hydrophobic dust filter is attached to the top of the filter gasket, covering the sensor ports
and the filters. The filter gasket and hydrophobic dust filter get replaced as a set.
NOTE: Some GX-3Rs have a hydrophobic dust filter that is not attached to the filter gasket. When
replacing the hydrophobic dust filter on one of these GX-3Rs, remove the filter and the gasket
and replace it with a filter gasket/hydrophobic dust filter assembly.
Infrared Communications Port
An infrared (IR) communications port is located on the top of the case, near the top LEDs. Logged data
transmits through the port in standard IrDA protocol. A computer’s infrared port or an IrDA/USB cable
connected to a USB port can be used to download data to the GX-3R Data Logger Management Program.
See the GX-3R Data Logger Management Program operator’s manual for data logging and downloading
instructions.
Charging Socket and Battery Pack
A charging socket on the back of the instrument allows for charging cable connection.
A lithium ion (Li-ion) battery pack powers the GX-3R. At 25°C the battery lasts at least 25 hours. The
battery icon in the upper right of the LCD shows remaining battery life.
A low battery warning activates when the GX-3R detects a low battery voltage. The GX-3R sounds a dead
battery alarm when battery voltage is too low for Measuring Mode.
The battery pack can be recharged by using the GX-3R charging cable. The battery pack is not user-
replaceable.
NOTE: Use of batteries or battery chargers not specified by RKI Instruments, Inc. will compromise the
CSA classification and may void the warranty. See “Recharging the Batteries” on page 73.
WARNING: To prevent ignition of a hazardous atmosphere, batteries must only be changed or
charged in an area known to be nonhazardous.
AVERTISSEMENT: Pour éviter l’inflammation d’une atmosphère dangereuse, les batteries doivent
uniquement être modifiés ou facturés dans une zone connue comme non
dangereuse.

14 • Chapter 2: Description GX-3R Condensed Operator’s Manual
Included Accessories
Alligator Clip
An alligator clip is installed on the back of the GX-3R. The alligator clip can be used to attach the GX-3R
to clothing or a belt. Teeth in the alligator clip’s jaws prevent the unit from slipping off.
Rubber Boot
A black rubber boot is installed on the GX-3R.
Wrist Strap
A wrist strap is included with the GX-3R and can be attached to the wrist strap installation feature on the
left side of the GX-3R’s case.
Single-Unit AC Charger
The charging cable is a 4 foot cable with an AC adapter on one end and a charging plug that connects to the
GX-3R on the other end.
Alligator Clip
Figure 2: Alligator Clip
Figure 3: Charging Cable
AC Adapter
Charging
Plug

GX-3R Condensed Operator’s Manual Chapter 2: Description • 15
Calibration Cup
Use the calibration cup to apply gas during a bump test, calibration, or gas test. The calibration cup has an
installation orientation to observe. “Front” and “rear” imprinting on the bottom of the cup correspond to
the front and rear of the GX-3R when the calibration cup is installed. In addition, a “front” label on the
front of the calibration cup should be visible when viewing the LCD with the calibration cup installed.
Other Accessories
12 VDC Charger
The 12 VDC charger is a 4 foot cable with a vehicle plug on one end and plug that connects to the GX-3R’s
power jack on the other end.
Multi-Unit AC Charger
The multi-unit charger is a 4 foot wall plug style adapter that plugs into a bar. The bar has five 2-foot
cables coming out one side. The end of each of the five cables has a plug that connects to the GX-3R’s
power jack. The AC adapter is rated 100 - 240 VAC input, 5.99 VDC output.
Belt Clip
A belt clip makes it easy to hook the GX-3R to a utility belt.
Figure 4: Calibration Cup
FRONT
Belt Clip
Figure 5: Belt Clip

16 • Chapter 2: Description GX-3R Condensed Operator’s Manual
SDM-3R
The SDM-3R is a calibration station for the GX-3R and GX-3R Pro. The station’s buttons can be used for
operations (Standalone Mode) or a computer can be used to control the docking station (PC Controlled
Mode). See the appropriate SDM-3R manual for more information.
RP-3R
The RP-3R is a pump that draws sample to the GX-3R. See the RP-3R manual for more information.
Aspirator Adapter
The aspirator adapter is a squeeze-bulb assembly that draws sample to the GX-3R.
IrDA Cable
Unless your computer has a built-in IrDA port, an IrDA cable is needed to establish communication
between the GX-3R and the Datalogging Program or the User Setup Program.

GX-3R Condensed Operator’s Manual Chapter 3: Operation • 17
Chapter 3: Operation
Overview
This chapter explains how to use the GX-3R to perform confined space entry monitoring or general area
monitoring in Measuring Mode.
Start Up
This section explains how to start up the GX-3R, get it ready for operation, and turn it off.
WARNING: A thin protective film covers the display to prevent scratches during shipping. Remove
this film before use. Leaving the film installed voids the intrinsically safe certification.
NOTE: The screens illustrated in this section are for a standard 4-gas unit. The screens displayed by
your GX-3R may be slightly different.
Turning On the GX-3R
To illustrate certain functions, the following description of the GX-3R start up sequence assumes that the
following menu items in User Mode are turned on: LUNCH, CAL RMDR, and BUMP.RMDR in User
Mode, and ID DISP and AUTOZERO in Maintenance Mode. If any of these items are turned off, then the
corresponding screens will not appear.
1. Press and briefly hold down POWER MODE. Confirm that the LCD turns on, the LEDs flash, the
buzzer sounds, and the motor vibrates before continuing with operation. Release the POWER MODE
button when you hear a beep.
2. If LUNCH is set to ON (factory setting if OFF, see page 47), the Lunch Break Screen appears. The
unit counts down from 5 seconds.
a. Continue Accumulating: To continue accumulating peak and time-weighted average (TWA)
readings from the last time the GX-3R was used, press and release POWER MODE or allow the
countdown to reach 0. The short-term exposure limit (STEL) reading is reset each time the GX-
3R is turned on.
b. Reset Accumulation: To reset the accumulation of peak and time-weighted average (TWA)
readings, press and release AIR before the countdown reaches 0.
RESUME
7:49
SEC
5

18 • Chapter 3: Operation GX-3R Condensed Operator’s Manual
3. If CAL RMDR is set to ON (factory setting) and a calibration is due, the screen that appears next
depends on how CAL EXPD is set in User Mode (see page 47). The three possible screens are
described below. If a calibration is not due, the instrument shows how many days are left until a
calibration is due.
CAL EXPD set to
CONFIRM (factory setting)
CAL EXPD set to
CANT USE
CAL EXPD set to
NONE
LCD
Sound Buzzer sounds double pulsing
tone
Buzzer sounds double pulsing
tone
None
Action • Option A, Perform calibration:
Press and release POWER
MODE to perform a calibration.
The instrument takes you
straight to the AUTO CAL CYL
A screen in User Mode’s GAS
CAL\AUTO CAL item. If
Password Protection is set to On
using the SDM-3R PC program,
you must enter a password. See
page 58 for calibration
instructions.
If the calibration is successful,
the screen above will not appear
again until the unit is due for
calibration. If the calibration is
not successful, the screen above
will again appear in the startup
sequence.
• Option B, Bypass message: To
continue without performing a
calibration, press and release
AIR.
The GX-3R cannot be used until a
successful calibration is per-
formed. Press and release
POWER MODE to perform a cal-
ibration. The instrument takes you
straight to the AUTO CAL CYL
A screen in User Mode’s GAS
CAL\AUTO CAL item. If Pass-
word Protection is set to On
using the SDM-3R PC program,
you must enter a password. If you
don’t press POWER MODE, the
instrument automatically goes to
the AUTO CAL CYL A screen
after 6 seconds. If Password Pro-
tection is set to On using the
SDM-3R PC program, you must
enter a password. See page 58 for
calibration instructions.
If the calibration is successful, the
screen above will not appear
again until the unit is due for cali-
bration. If the calibration is not
successful, the screen above will
again appear in the startup
sequence.
• Option A, Perform calibration:
To perform a calibration, press
and release POWER MODE.
The instrument takes you
straight to the AUTO CAL CYL
A screen in User Mode’s GAS
CAL\AUTO CAL item. If
Password Protection is set to
On using the SDM-3R PC
program, you must enter a
password.
• Option B, Bypass message: To
continue without performing a
calibration, wait a few seconds
for the instrument to continue
with its startup sequence.
CAL--LMT
7:49
CAL
CAL--LMT
7:49
FAIL
NEXT CAL
7:49
0 d

GX-3R Condensed Operator’s Manual Chapter 3: Operation • 19
4. If BUMP.RMDR is set to ON (factory setting is OFF) and a bump test is due, the screen that appears
next depends on how BUMP.EXPD is set in User Mode (see page 47). The three possible screens are
described below. If a bump test is not due, the instrument shows how many days are left until a bump
test is due.
5. The Date/Time Screen appears for a few seconds.
BUMP.EXPD set to
CONFIRM (factory setting)
BUMP.EXPD set to
CANT USE
BUMP.EXPD set to
NONE
LCD
Sound Buzzer sounds double pulsing tone Buzzer sounds double pulsing tone None
Action • Option A, Perform bump test:
Press and release POWER
MODE to perform a bump test.
The instrument takes you straight
to the BUMP CYL A screen in
User Mode’s BUMP item. If
Password Protection is set to On
using the SDM-3R PC program,
you must enter a password. See
page 51 for bump test
instructions.
If the bump test is successful, the
screen above will not appear
again until the unit is due for
bump testing. If the bump test is
not successful, the screen above
will again appear in the startup
sequence.
• Option B, Bypass message: To
continue without performing a
bump test, press and release AIR.
The GX-3R cannot be used until a
successful bump test has been per-
formed. Press and release POWER
MODE to perform a bump test. The
instrument takes you straight to the
BUMP CYL A screen in User
Mode’s BUMP item. If Password
Protection is set to On using the
SDM-3R PC program, you must
enter a password. If you don’t press
POWER MODE, the instrument
automatically goes to the BUMP
CYL A screen after 6 seconds. If
Password Protection is set to On
using the SDM-3R PC program, you
must enter a password. See page 51
for bump test instructions.
If the bump test is successful, the
screen above will not appear again
until the unit is due for bump testing.
If the bump test is not successful, the
screen above will again appear in the
startup sequence.
• Option A, Perform bump test: To
perform a bump test, press and
release POWER MODE. The
instrument takes you straight to
the BUMP CYL A screen in User
Mode’s BUMP item. If
Password Protection is set to
On using the SDM-3R PC
program, you must enter a
password.
• Option B, Bypass message: To
continue without performing a
bump test, wait a few seconds for
the instrument to continue with
its startup sequence.
BUMP--LMT
7:49
CAL
BUMP--LMT
7:49
FAIL
NEXT BP
7:49
0 d
7:49
7:49
18 - 12.22

20 • Chapter 3: Operation GX-3R Condensed Operator’s Manual
6. The Battery Voltage Screen appears for a few seconds.
An “AL-L” at the bottom of the screen indicates that the alarms are set to latching. An “AL-A” at
the bottom of the screen indicates that the alarms are set to auto reset. See page 71 for a description
of how to change this parameter.
7. The combustible gas sensor contains 2 separate sensors: a standard catalytic sensor and a backup,
poison-resistant sensor that is resistant to sensor poisons like silicone. An HC Gas List alarm indicates
that the standard sensor has a reduced output, possibly due to one or more sensor poisons in the
environment, and that the poison-resistant sensor is being used to provide gas readings. The poison-
resistant sensor has a limited list of detectable gases. See Table 10 on page 40 for which gases can and
cannot be detected during an HC Gas List condition.
Depending on the version, one of the following screens appears, the LEDs flash, and the instrument
beeps.
Press and release POWER MODE to confirm the HC Gas List screen and continue to the Gas
Name Screen. If POWER MODE is not pressed after 5 seconds, the GX-3R will automatically
proceed to the next screen.
NOTE: If your application requires detection of a gas still detectable after an HC Gas List
condition (like methane or isobutane), there is no need to replace the combustible
gas sensor.
However, if your application requires detection of a gas not detectable after an HC
Gas List condition (like methanol or ethanol), you must replace the combustible gas
sensor as soon as possible.
8. The following screens display for 3 seconds each: the Gas Name Screen, the Full Scale Screen, the
Warning Setpoint Screen, the Alarm Setpoint Screen, the Alarm H Setpoint Screen, the STEL Alarm
Screen, and TWA Alarm Screen.
NOTE: If the combustible gas is set to something other than CH4 or H2 in Gas Select
Mode, the combustible channel is displayed as “HC” and the gas formula for the
combustible gas sensor’s target gas appears during startup.
AL - L V
7:49
3.8
bAtt
MANUAL
7:49
LISt In
rEAd GAS
LIMITED
7:49
GAS LIST
HC
ROM versions 07253 or later ROM versions 07104 or earlier