Riken Keiki GX-2001 User manual

Model GX-2001
Operator’s Manual
2-7-6 Azusawa Itabashi-ku Tokyo,

Warranty
RIKEN KEIKI CO., LTD.., warrants gas alarm equipment sold by us to be free
from defects in materials and workmanship, and performance for a period of
one year from date of shipment from RIKEN KEIKI CO., LTD.. Any parts found
defective within that period will be repaired or replaced, at our option, free of
charge. This warranty does not apply to those items which by their nature are
subject to deterioration or consumption in normal service, and which must be
cleaned, repaired, or replaced on a routine basis. Examples of such items are:
Absorbent cartridges Batteries
Pump diaphragms and valves Filter elements
Fuses
Warranty is voided by abuse including mechanical damage, alteration, rough
handling, or repairs procedures not in accordance with the instruction manual.
This warranty indicates the full extent of our liability, and we are not
responsible for removal or replacement costs, local repair costs, transportation
costs, or contingent expenses incurred without our prior approval.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER WARRANTIES
AND REPRESENTATIONS, EXPRESSED OR IMPLIED, AND ALL OTHER
OBLIGATIONS OR LIABILITIES ON THE PART OF RIKEN KEIKI CO., LTD..,
INCLUDING BUT NOT LIMITED TO THE WARRANTY OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL RIKEN KEIKI
CO., LTD.., BE LIABLE FOR INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
LOSS OR DAMAGE OF ANY KIND CONNECTED WITH THE USE OF ITS PRODUCTS
OR FAILURE OF ITS PRODUCTS TO FUNCTION OR OPERATE PROPERLY.
This warranty covers instruments and parts sold to users only by authorized
distributors, dealers, and representatives as appointed by RIKEN KEIKI CO.,
LTD..
We do not assume indemnification for any accident or damage caused by the
operation of this gas monitor and our warranty is limited to replacement of
parts or our complete goods.

Table of Contents
Introduction ...................................................................................1
Specifications..................................................................................2
Description .....................................................................................3
Case .......................................................................................................... 3
Sensors ...................................................................................................... 3
LCD............................................................................................................ 4
Control Buttons............................................................................................ 4
Printed Circuit Boards .................................................................................... 5
Alarm Lights.................................................................................................5
Buzzer/Vibrator ........................................................................................... .5
Ni-cad Battery Pack...................................................................................... 5
Belt Clip...................................................................................................... 5
Battery Charger............................................................................................ 5
Start Up ........................................................................................ 6
Start-up Procedure...................................................................................... 6
Performing a Demand Zero............................................................................. 6
Turning Off the Model GX-2001 ...................................................................... 6
Operation...................................................................................... 7
Normal Operation.......................................................................................... 7
Displaying Peak Readings............................................................................... 7
Displaying STEL and TWA Readings .................................................................8
Alarms ....................................................................................................... 8
Displaying and Setting the Alarm Points...........................................11
Setting the Time and Date .............................................................13

Calibration....................................................................................14
Setting the Zero Readings for All Target Gasses ................................................14
Single Calibration.........................................................................................14
Auto Calibration...........................................................................................16
Maintenance.................................................................................18
Troubleshooting...........................................................................................18
Recharging the Ni-cad Battery Pack ...............................................................19
Replacing the Ni-cad Battery Pack..................................................................19
Replacing the Sensor Cover ...........................................................................20
Replacing a Sensor................................................................................................................................................20

Introduction
Using an advanced detection system consisting of four gas sensors, the Model
GX-2001 Personal Four-Gas Monitor detects the presence of combustible gas,
oxygen (O2), carbon monoxide (CO), and hydrogen sulfide (H2S)
simultaneously. The Model GX-2001’s compact size and easy-to-use design
makes 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 Model GX-2001 offers a full range of features, including:
lSimultaneous four-gas monitoring of combustible gases, O2, CO, and H2S
lLiquid crystal display (LCD) for complete and understandable information at
a glance
lDistinctive audible alarms for dangerous gas conditions and for unit
malfunction
lMicroprocessor control for reliability, ease of use, and advanced
capabilities
lAlarm trend data
lData logging functions
lSTEL/TWA and ceiling alarm display
lPeak hold and average readouts
lBuilt-in time function
lRF shielded and high impact plastic case of very compact size and light
weight
lBelt clip for “hands-free” gas monitoring
lCSA classified for Class I, Division I, Groups A, B, C, and D hazardous
atmospheres
WARNING: The Model GX-2001 detects oxygen deficiency and elevated
levels of oxygen, combustible gases, carbon monoxide, and
hydrogen sulfide, all of which can be dangerous or life
threatening. When using the Model GX-2001, 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.

Specifications
Table 1 : Model GX-2001 Specifications
Model Name Model GX-2001
Target Gas Combustibles
(HC, CH4, etc.) Oxygen (O2) Hydrogen Sulfide (H2S) Carbon Monoxide (CO)
Range
(Increment) 0-100% LEL (1% LEL) 0-40.0 vol% (0.1 vol%) 0-150 ppm (0.5 ppm) 0-300 ppm (1 ppm)
Detection Method Diffusion
Response Time T90 Within 30 Seconds
Display 7-Segment Digital LCD
Gas Alarms
(Factory Settings) Alarm 1: 10% LEL Alarm 2: 50% LEL
Over: 100% LEL
Alarm 1: 19.5 vol%
(Decreasing)
Alarm 2: 23.5 vol%
Over: 40.0 vol%
Alarm 1: 10 ppm
Alarm 2: 30 ppm
TWA: 10 ppm
STEL: 15 ppm
Alarm 1: 25 ppm
Alarm 2: 50 ppm
TWA: 25 ppm
STEL: 200 ppm
Operating
Temperature and
Humidity
-10 to 40o C/Below 85% RH (Without Condensation)
Power Supply Ni-cad Battery Pack (2.4 VDC Nominal), Direct Charging
Continuous
Operating Hours Up to 12 Hours (No Alarms after Full Charge)
Case High-impact Plastic, RF Shielded, Dust and Weather Proof
Standard
Accessories Ni-Cad Battery Pack, Belt Clip
Optional
Accessories
• Charging Station, 115 VAC Powered
• Charging Station with PC Communication Function for Datalog
Downloading
• Communication Computer Cable
• Communication Software (Windows® 95, 98, & NT)
• Automatic Calibraiton Station
• Hand Aspirated Sample Draw with Hose and Probe
• Wrist Strap
Dimensions and
Weight Dimensions: 2.8 (H), 2.2 (W), 1.1 (D) inches Weight: Approximately 6 oz.

Description
This section describes the components of the Model GX-2001. These
components include the Model GX-2001’s case, sensors, LCD, control buttons,
printed circuit boards, alarm lights, buzzer/vibrator, Ni-cad battery pack, belt
clip, and battery charger.
Case
The Model GX-2001’s sturdy, high-impact plastic and metal case is radio
frequency (RF) resistant, and is suitable for use in many environmental
conditions, indoors and out. The unit is dust proof and weather resistant..
On the front of the case is a digital LCD, which shows gas concentrations,
battery level, time, and other readings including TWA, STEL, and peak gas
levels. Below the LCD are three control buttons. The first button on the left is
labeled MODE/POWER. The other buttons are labeled DISP and AIR,
respectively.
Beneath the control buttons is the buzzer, which is located inside the unit.
On the right side of the Model GX-2001 are the diffusion ports for the gas
sensors located inside the case. These sensors are, from top to bottom (and
are marked on the case), HC (combustible gases), O2, CO, and H2S.
On the left side of the case are two brass recharging contacts, which are used
when the unit is placed in the battery charger, and on top of the case are two
alarm lights. On the back of the unit is a rugged metal belt clip enabling hands-
free gas monitoring.
Sensors
The Model GX-2001 uses four sensors to monitor HC (combustible gases), O2,
CO, and H2S simultaneously. The sensors are protected by filters that allow
atmosphere to diffuse inward. The sensors use different detection principles,
as described below.
Combustible Gas Sensor
The LEL sensor detects combustible gas and vapors in the atmosphere with a
catalytic platinum element. The reaction of gas with oxygen on the catalyst
causes a change in the resistance of the element. The current is amplified by
the Model GX-2001’s circuitry, converted to a measurement of combustible gas
concentration, and displayed on the LCD.
Oxygen Sensor
The O2sensor is an electrochemical cell. 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 Model GX-
2001’s circuitry, converted to a measurement of gas concentration, and
displayed on the LCD.
CO and H2S Sensors

The CO and H2S sensors are electrochemical cells that consist of two precious
metal electrodes in an acid electrolyte. A gas permeable membrane covers the
cell and allows gas to diffuse into the electrolyte. The gas reacts in the cell
and produces a current proportional to the concentration of the target gas.
The current is amplified by the Model GX-2001’s circuitry, converted to a
measurement of gas concentration, and displayed on the LCD.
LCD
The LCD is visible through the GX-2001’s front panel. Target gas
concentrations, the time, battery condition, and alarm indications are
displayed on the LCD.
Control Buttons
Below the LCD are the control buttons. These buttons are MODE/POWER,
DISP, and AIR. They turn on the power to the Model GX-2001, and turn it off.
They control what is displayed on the LCD, including battery level, time, date,
and year, gas concentrations, peak, TWA, and STEL readings, as well as other
messages. They also allow you to perform a Demand Zero, change alarm
points, change the date and time, and calibrate the instrument. The functions
performed by the control buttons are summarized in the following table:
Table 2 : The Control Buttons of the Model GX-2001
Button Function
MODE/POWER • Turns the unit on and off.
• Turns the LCD back light on and off.
•
Displays peak readings (low minimum and high maximum readings
for O2).
• Resets the alarm circuit (gas alarms).
• Enters Calibration Mode with the AIR button.
• Enters Alarm Adjustment Mode with the AIR button.
• Enters Time Adjustment Mode with the DISP button.
DISP • Displays the next target gas when the unit is in Measuring Mode.
• Enters Time Adjustment Mode with the MODE/POWER button.
• Decreases settings when the unit is in Alarm Adjustment Mode or
Time Adjustment Mode.
• Toggles between field calibration and auto calibration when the
unit is in Calibration Mode.
AIR • Adjusts LCD readings when the a Demand Zero is performed.
• Enters Calibration Mode with the MODE/POWER button.
• Enters Alarm Adjustment Mode with the MODE/POWER button.
• Increases settings when the unit is in Alarm Adjustment Mode or
Time Adjustment Mode.
• Toggles between field calibration and auto calibration when the
unit is in Calibration Mode.

Printed Circuit Boards
The primary function of the Model GX-2001’s three printed circuit boards are to
amplify the current sent to them from the four gas sensors, convert the
current to a meaningful measurement of gas concentration, display the gas
concentration on the LCD, store peak, STEL, and TWA readings, and activate
the alarm circuit if an alarm point has been reached. They monitor battery
level, battery failure, and sensor failure. They also control the Model GX-2001’s
time function and the various operating modes of the unit. Note that the
printed circuit boards contain no serviceable parts.
Alarm Lights
The Model GX-2001 has two alarm lights mounted on top of the unit. The alarm
lights are two red LEDs that alert you to gas, low battery, and sensor failure
alarms.
Buzzer/Vibrator
A solid-state electronic buzzer/vibrator is mounted inside the front case of the
Model GX-2001. The buzzer/vibrator sounds and vibrates for gas alarms, and
it sounds for unit malfunctions, low battery voltage, and as an indicator during
normal use of the many display options of the Model GX-2001.
Ni-cad Battery Pack
Inside the Model GX-2001 is a Ni-cad battery pack that supplies 2.4 V to the
unit. The battery will run the unit for approximately 12 hours when no alarms
have been activated during that time period. The battery is fully rechargeable
when the Model GX-2001 is placed into the battery charger. The battery icon
on the LCD shows the charge remaining in the battery. When the Model GX-
2001 detects a low battery voltage, a low battery warning is activated. The
battery can be replaced by removing the belt clip on the back of the Model
GX-2001. See the maintenance section of this manual for instructions about
recharging and replacing the battery.
Belt Clip
On the back of the Model GX-2001 is a belt clip. The belt clip permits the unit
to be worn on a belt or to be clipped to a pocket for hands-free gas
monitoring.
Battery Charger
The Model GX-2001 has two optional battery chargers. Both are used to
recharge the unit’s Ni-cad battery pack and both serve as a convenient
station for auto calibration. The battery charger with the PC communication
feature has a datalogging port for the down loading of data from the Model
GX-2001 to the PC. See “Parts List” for more information.

Start Up
This section explains how to start up the Model GX-2001 and to get it ready
for operation.
Start-up Procedure
1. Press and hold the MODE/POWER button for one second to turn on the
Model GX-2001 and to activate its LCD. The alarm lights flash and the
buzzer sounds.
2. The Model GX-2001 tests all elements of the LCD, then displays the year,
month, day, and time before displaying the battery voltage. The buzzer
sounds again after the battery voltage is displayed.
CAUTION: If the battery level is low or if the battery icon is flashing and the
unit’s buzzer sounds, recharge the Model GX-2001’s Ni-cad
battery.
3. The four gas sensors inside the Model GX-2001 begin working, and the
concentrations of the target gases are displayed on the LCD in sequential
order beginning with oxygen. The Model GX-2001 is now in Measuring
Mode.
In Measuring Mode, battery level, time, and gas concentrations are
displayed on the LCD. The Model GX-2001 cycles through the four target
gases, starting with O2, then H2S, CO, and HC. Oxygen is displayed as a
percentage (%), H2S and CO as parts per million (ppm), and HC
(combustible gases) as a percentage of the lower explosive limit (% LEL).
NOTE: You can test the oxygen sensor and alarm circuit by exhaling into the
oxygen sensor. When the LCD reading falls below the alarm point for
oxygen, the buzzer will sound, the vibrator will activate, the LCD
reading for oxygen will flash, and the alarm lights will turn on.
Performing a Demand Zero
Before using the Model GX-2001, it is a good idea to set the zero reading
(demand zero) for the target gasses to ensure accurate gas readings in the
monitoring environment.
1. Find a fresh-air environment.
2. With the unit on and in Measuring Mode, press and hold the AIR button for
about three seconds to allow the Model GX-2001 to set the zero reading
for HC, CO, and H2S and to set the span for O2.
3. While you are pressing the AIR button, the LCD displays “Hold,” a prompt
for you to keep pressing the AIR button.
4. When the zero readings have been set, the LCD displays “Adj,” which
prompts you to release the AIR button.
Turning Off the Model GX-2001
1. Press and hold the MODE/POWER button for about five seconds to turn off
the unit.
2. The buzzer will sound and the LCD back light will flash.
3. Release the button when the LCD is blank. The unit is off.

Operation
This section describes the normal operation of the Model GX-2001. It explains
how the unit can be used to display peak gas readings of the four target
gasses and to display STEL and TWA readings for H2S and CO. This section
also covers alarm indications.
Normal Operation
After you have powered up the Model GX-2001 and performed a demand zero
for the four target gasses following the instructions of the previous section,
“Start Up,” the Model GX-2001 is in Measuring Mode.
In Measuring Mode, the battery level, time, and gas concentrations are
displayed on the LCD. The Model GX-2001 cycles through the four target
gases, starting with O2, then H2S, CO, and HC. Oxygen is displayed as a
percentage (%), H2S and CO as parts per million (ppm), and HC (combustible
gases) as a percentage of the lower explosive limit (% LEL).
Displaying Peak Readings
You can display peak readings of the four target gasses when the Model GX-
2001 is in Measuring Mode using the MODE/POWER and DISP buttons. With
oxygen, you can display both peak and minimum readings.
1. Make sure the Model GX-2001 is in Measuring Mode. The four target gasses
should be displaying in sequential order on the LCD.
2. Press the MODE/POWER button once to put the Model GX-2001 in Peak
Reading Mode. A small peak (minimum for O2) symbol is displayed in the
lower left corner of the LCD.
3. Press the DISP button to cycle through the four target gases. The peak
readings of these gasses are displayed on the LCD.
NOTE: Oxygen has both a peak and minimum reading.
4. To return to Measuring Mode, normal operation, press and release the
MODE/ POWER button until the normal screen is displayed.
NOTE: While in Peak Reading Mode, if no control button has been pushed for
about 15 seconds, the Model GX-2001 returns to Measuring Mode
automatically.
O2
20.9
21:19
%
T
a
r
g
et gas
Battery
char
g
e
Gas concentration
T
i
me
Figure 1: LCD in Measuring Mode

Displaying STEL and TWA Readings
With the Model GX-2001, you can display STEL and TWA readings for H2S and
CO. STEL is an acronym for short-term exposure limit, and it shows the
average reading for H2S and CO during the last 15 minutes. TWA is an acronym
for time-weighted average, and it shows the average reading for H2S and CO
during the last eight (8) hours. If eight (8) hours has not elapsed since the
last time the STEL/TWA readings were cleared, the TWA is still calculated over
eight hours, with the missing time assigned a zero (0) value for the readings.
1. Make sure the Model GX-2001 is in Measuring Mode. The four target gasses
should be displaying in sequential order on the LCD.
2. Using the DISP button, display either H2S or CO on the LCD.
3. With either H2S or CO displayed on the LCD, press the MODE/POWER button
twice to put the Model GX-2001 in STEL Reading Mode. “STEL” displays
next to the time reading on the LCD.
4. To put the Model GX-2001 in TWA Reading Mode, press the MODE/POWER
button again while the unit is in STEL Reading Mode. “TWA” displays next
to the time reading on the LCD.
5. Press the DISP button to toggle between the TWA reading for H2S and CO.
6. To return to Measuring Mode, normal operation, press the MODE/POWER
button.
NOTE: While in STEL or TWA Reading Mode, if no control button has been
pushed for about 15 seconds, the Model GX-2001 returns to Measuring
Mode automatically.
Alarms
This section covers alarm indications, or the types of alarms you will encounter
when using the Model GX-2001, including multiple alarms and trouble alarms. It
also tells you how to reset the Model GX-2001 after an alarm has occurred and
how to respond to an alarm condition.
Alarm Indications
The Model GX-2001 will sound an alarm and the unit will vibrate when one of
the target gas concentrations rises above the first alarm point, or in the case
of oxygen, falls below the low point alarm setting for that gas.
The Model GX-2001 also sounds an alarm and vibrates when the second alarm
point is reached for HC, CO, and H2S, when the concentration of oxygen rises
above 23.5% in the monitoring area, and when the STEL and TWA alarm points
are reached for CO and H2S.
When a trouble condition occurs, such as a sensor failure or low battery
charge, the unit will also sound an alarm but it will not vibrate.

The table below summarizes the types of alarms produced by the Model GX-2001.
Table 3 :
Alarm Type LCD Indications Other Indications
Alarm 1
Concentration of gas rises
above the first alarm point,
or for O2, falls below the
low point setting.
•
Name of gas displayed.
• Alarm light flashes.
• Back light turns on.
• Gas reading flashes.
Pulsing Tone
Unit Vibrates
Alarm 2
Concentration of gas rises
above second alarm point,
or for O2, rises above the
high point setting.
•
Name of gas displayed.
• Alarm light flashes.
• Back light turns on.
• Gas reading flashes.
Pulsing Tone
Unit Vibrates
TWA or STEL
Concentration of CO or
H2S rises above the TWA
or STEL alarm point
setting.
•
Name of gas displayed.
• Alarm light flashes.
• Back light turns on.
• TWA or STEL blinking.
Pulsing Tone
Unit Vibrates
Over Range •
Name of gas displayed.
• Gas reading replaced
by blinking brackets.
• Alarm light flashes.
• Back light turns on.
Pulsing Tone
Unit Vibrates
Low Battery Warning • Battery icon flashes. None
Dead Battery Alarm • Gas reading replaced
by FAIL.
• Battery icon flashes.
Double Pulsing Tone
Sensor Failure • Name of gas sensor
displayed.
• Gas reading replaced
by FAIL.
Double Pulsing Tone

Multiple Alarms
If more than one gas alarm is activated, the LCD shows the concentration of
the gas that triggered the last alarm. To see the concentration of the other
gasses, press the DISP button until the gas of interest is displayed. When the
DISP button is pressed, the displayed gas will stay displayed for 20 seconds,
then the display will cycle.
For example, if concentrations of CO and H2S in the monitoring environment
were to rise above their respective alarm points and CO was the first to do so,
the concentration of H2S would display on the LCD. Pressing the DISP button
would display the concentration of CO for 20 seconds, then HC for three
seconds, etc.
If the TWA and STEL alarms are triggered, alarm indications for both gasses
occur at the same time. The LCD would then display both “TWA” and “STEL”
next to the time and both “TWA” and “STEL” would be blinking.
Resetting Alarms
To reset an alarm, press the MODE/POWER button after the gas reading falls
below the Alarm 1 point (or above for oxygen). If a TWA alarm has been
activated, it cannot be reset unless you turn off the unit.
• Even though gas concentrations may have returned to normal or have
fallen below the alarm point, the alarm indications will continue until
you have reset the alarm using the MODE/POWER button.
Responding to Alarms
This section describes response to gas, over range, battery, and sensor failure
alarms.
Responding to Gas Alarms
1. Determine which gas alarm has been activated.
2. Follow your established procedure for an increasing gas condition or a
decreasing oxygen condition.
3. Reset the alarm using the MODE/POWER button once the alarm condition
has been cleared.
Responding to Over Range Alarms
WARNING: An over range condition my indicate an extreme combustible
gas , toxic gas, or oxygen content condition. Confirm a
normal condition with a different Model GX-2001 or with
another gas detecting device.
1. Determine which gas alarm has been activated.
2. Follow your established procedure for an increasing gas condition.
3. Reset the alarm using the MODE/POWER button once the alarm condition
has cleared.
4. Calibrate the Model GX-2001 as described in the calibration section of this
manual.
5. If the over range condition continues, you may need to replace the sensor
that has triggered the over range alarm.
6. If the over range condition continues after you have replaced the sensor,
contact RIKEN KEIKI CO., LTD.. for further instructions.

Responding to Battery Alarms
WARNING: The Model GX-2001 is not operational as a gas monitoring
device during a dead battery alarm. Take the Model GX-2001
to a non-hazardous area and recharge the battery as
described in “Recharging the Ni-cad Battery.”
The Model GX-2001 is fully functional during a low battery warning. However,
depending upon conditions, the Model GX-2001 has only two-to-three hours of
operating time left after the low level battery alarm has been triggered.
Recharge the battery pack as soon as possible as described in “Recharging the
Ni-cad Battery Pack.”
NOTE: Alarms and the back light feature consume battery power and reduce
the amount of operating time remaining.
Responding to Sensor Failure Alarms
1. Determine which sensor has triggered the sensor failure alarm.
2. Try calibrating the sensor first, as described in “Calibration,” before
replacing it.
3. If the sensor failure continues, replace the sensor as described in
“Replacing a Sensor.”
4. If the sensor failure condition continues after you have replaced the
sensor, contact RIKEN KEIKI CO., LTD.. for further instructions.
Displaying and Setting the
Alarm Points
The Model GX-2001 allows you to display and set the alarm points of the four
target gasses. Each of the target gasses has both a low (Alarm 1) and high
(Alarm 2) alarm setting. Two gasses, CO and H2S, have STEL and TWA alarm
points. The alarm point for oxygen is measured as a percentage of oxygen in
the atmosphere. The alarm point for HC is measured as a percentage of the
lower explosive limit (% LEL), and CO and H2S alarm points are measured in
parts per million (ppm). The alarm points and their factory settings are
summarized in the table below:
Table 4 : Alarm Points of the Four Target Gasses
Gas Alarm 1 Alarm 2 STEL TWA
O2 19.5%
(Decreasing) 23.5% None None
HC
(Combustibles)
10% LEL 50% LEL None None
CO 25 ppm 50 ppm 400 ppm 25 ppm
H2S 10 ppm30 ppm 15 ppm 10 ppm

In the table above, Alarm 1 and Alarm 2 for HC, CO, and H2S refer to a rising
concentration of these gasses. The first alarm is triggered at the Alarm 1
concentration listed in the table. For HC that would be 10% LEL, for CO that
would be 25 ppm, and for H2S that would be 10 ppm. The second alarm is
triggered when the Alarm 2 concentration is reached. For oxygen, Alarm 1 is
triggered when the concentration of oxygen falls below 19.5%. When the
concentration of oxygen rises above 23.5%, Alarm 2 is activated.
Display and Adjust the Alarm Points
1. Make sure the Model GX-2001 is turned off. The LCD should be blank.
2. Press and hold the AIR button, then press and hold the MODE/POWER
button.
3. As soon as segments appear on the display (approximately one second),
release the AIR button. When the unit “beeps,” release the MODE/POWER
button to put the Model GX-2001 into Alarm Point Adjustment Mode. The
LCD should show the Alarm 1 setting for O2and the battery level.
NOTE: If the LCD should show “CAL,” the Model GX-2001 is in Calibration
Mode. You will need to press and hold the MODE/POWER button to turn
off the unit. Begin again with step 2 above.
4. Use the MODE/POWER button to cycle through the alarm points of the
target gasses. Oxygen is displayed first followed by H2S, CO, then HC. Use
the AIR button to increase the alarm point and the DISP button to
decrease the alarm point. When using the MODE/POWER button, press it
once to display the next reading. If you press and hold the MODE/POWER
button, you may turn off the unit.
NOTE: You can only cycle through the target gasses once before the Model
GX-2001 goes into Start-up Mode followed by Measuring Mode. If you
want to cycle through the gasses again, press and hold the
MODE/POWER button to turn off the Model GX-2001. Then begin with
step 2 above to put the unit back into Alarm Point Adjustment Mode.
5. When you are finished viewing or adjusting the alarm point settings, press
the MODE/ POWER button repeatedly until the ROM number for your unit
appears on the LCD. (the ROM is the component that contains the
software that runs the Model GX-2001.) The Model GX-2001 will then go
into Start-up Mode followed by Measuring Mode.
O2
19.5
LO
%
T
a
r
g
et
gas
Batter
y
char
g
e
Gas
concentration
Figure 2: LCD in Alarm
Adjustment Mode
Alarm
point
.

Setting the Time and Date
The Model GX-2001 allows you to set the time and date.
1. Make sure the Model GX-2001 is turned off. The LCD should be blank.
2. Press and hold the DISP button, then press and hold the MODE/POWER
button to put the Model GX-2001 into Time Adjustment Mode. Release the
buttons when the unit beeps. The LCD shows the year, month, day, and
time. The year is flashing at the top of the LCD.
3. To change the time and date,
• Use the MODE/POWER button to cycle through the time and date
values.
• You can only change a value if it is flashing.
• Use the AIR button to increase a value.
• Use the DISP button to decrease a value.
NOTE: Once you have cycled though the time and date values, the Model GX-
2001 will go into Start-up Mode followed by Measuring Mode. If you
want to cycle through the time and date values again, press and hold
the MODE/POWER button to turn off the Model GX-2001. Then begin
with step 2 above to put the unit back into Time Adjustment Mode.
4. To leave Time Adjustment Mode, press the MODE/POWER button to cycle
through to the end of the time and date values. The Model GX-2001 then
enters Start-up Mode followed by Measuring Mode.
2000
11.13
21:06
Year
Month Day
Hour Minute
Figure 3: LCD in T ime Adjustment Mode

Calibration
This section covers the calibration of the Model GX-2001. Setting the zero
reading is described first followed by single calibration and auto calibration. For
single calibration, you are told what is needed to complete the task, how to
assemble the calibration kit, and how to set the span readings of the four
target gasses. The same topics are covered for auto calibration.
Setting the Zero Readings for All Target Gasses
Whether you will calibrate the Model GX-2001 using single calibration or auto
calibration, you will need to set the zero readings first before setting the span
readings for each gas.
1. Find a fresh-air environment.
2. Turn on the Model GX-2001 by pressing and holding the MODE/POWER
button for one second.
3. Press and hold the AIR button for about three seconds to allow the Model
GX-2001 to set the zero reading for HC, CO, and H2S and to set the span
for O2.
4. While you are pressing the AIR button, the LCD displays “Hold,” a prompt
for you to keep pressing the AIR button.
5. When the zero readings have been set, the LCD displays “Adj,” which
prompts you to release the AIR button.
Single Calibration
This section tells you how to calibrate the Model GX-2001 using the single
calibration (CAL) menu.
Preparation
Before you calibrate the Model GX-2001, you must set the zero readings as
described in “Setting the Zero Readings for All Target Gasses.” You will also
need the supplies listed below. Calibration kits from RIKEN KEIKI CO., LTD.. are
available for this purpose (see “Parts List”).
• Either a 3-gas or 4-gas calibration cylinder with the following recommended
concentrations:
• 50% LEL methane (CH4)
• 12 % oxygen
• 50 ppm CO
• 10 ppm H2S (4-gas cylinder only)
• Balance of nitrogen
• To carry out the calibration, you will need a fixed-flow regulator with a flow
rate of 0.5 LPM (liters per minute), non-absorbent tubing, and a calibration
adapter plate that will fit over the Model GX-2001’s four sensors.

Assembling the Calibration Kit
WARNING: Calibrate the Model GX-2001 in a non-hazardous
environment.
1. Attach the adapter plate to the unit. It snaps onto the sensor area.
2. Attach the calibration tubing to the adapter plate, then attach the
opposite end of the tubing to the regulator.
NOTE: Do not attach the regulator to the gas cylinder at this time.
If you are going to calibrate the Model GX-2001 for all the target
gasses at one time, it is recommend that you start with the oxygen
sensor first followed by the H2S, CO, and HC sensors in that order.
The reason for this calibration sequence is that while the Model GX-
2001 is in Calibration Mode, you will only be able to toggle through the
target gasses one time, using the MODE/POWER button, before the
unit goes into its start-up sequence.
If you want to go back to a target gas, you will need to turn off the
Model GX-2001 before putting the unit back into Calibration Mode.
Setting the Span Readings for All Target Gasses
When setting the span readings manually for one gas sensor at time, you will
calibrate each gas sensor individually.
1. Make sure you have set the zero readings for all the target gasses and
have set up the calibration kit as described in the procedure above. If you
are going to calibrate all the target gasses, start with O2followed by H2S,
CO, and HC.
2. Make sure the Model GX-2001 is off.
3. Press and hold the AIR button, then press and hold the MODE/POWER
button. Release both buttons when you hear a “beep.” The LCD displays
“CAL,” the battery level, and the time.
4. Pressing the MODE/POWER button allows you to toggle through each target
gas once so you can calibrate that gas. In the upper left corner of the
LCD, “CAL” and the name of the target gas being calibrated, such as “O2,”
are displayed alternately in rapid succession.
5. Attach the regulator to the gas cylinder. The fixed-flow regulator
automatically begins introducing the calibration sample to the sensors.
6. Let the gas flow for two minutes before adjusting the span.
7. Use the AIR button to in increase the reading and the DISP button to
decrease the reading until you have matched the concentration of the
calibration sample.
NOTE: If you cannot adjust the display reading to match the calibration
sample, you may need to replace the sensor you are calibrating, as
described in “Replacing a Sensor.”

8. After you have set the span for the sensor, press the MODE/POWER button
to display the next sensor. In the upper left corner of the LCD, “CAL” and
the name of the target gas being calibrated, such as “H2S” are displayed
alternately in rapid succession.
9. Repeat steps 7 and 8 above to set the span for the remaining target
gasses.
10. When you are finished setting the span for the target gasses, remove the
regulator from the cylinder, remove the adapter plate from the unit, then
store the contents of the calibration kit in a safe place for future use.
11. Use the MODE/POWER button to place the Model GX-2001 in Measuring
Mode or to turn the unit off.
Auto Calibration
This section tells you how to calibrate the Model GX-2001 using the auto
calibration (AUTO CAL) menu.
Preparation
Before you calibrate the Model GX-2001, you must set the zero readings as
described in “Setting the Zero Readings for All Target Gasses.” You will also
need the supplies listed below. Calibration kits from RIKEN KEIKI CO., LTD.. are
available for this purpose (see “Parts List”).
• Either a 3-gas or 4-gas calibration cylinder with the following recommended
concentrations:
• 50% LEL methane (CH4)
• 12 % oxygen
• 50 ppm CO
• 10 ppm H2S (4-gas cylinder only)
• Balance of nitrogen
• To carry out the calibration, you will need a fixed-flow regulator with a flow
rate of 0.5 LPM and non-absorbent tubing.