PT2E-1943

2-Wire Gas Detector HeadGD-F88Ai
Operating Manual(PT2-194)

Contents
1. Outline of the Product ..................................................................................................................................... 1
1-1. Preface ................................................................................................................................................... 1
1-2. Purpose of use ....................................................................................................................................... 1
1-3. Definition of DANGER, WARNING, CAUTION and NOTE .................................................................... 1
2. Important Notices on Safety ........................................................................................................................... 2
2-1. Danger cases ......................................................................................................................................... 2
2-2. Warning cases ........................................................................................................................................ 2
2-3. Precautions ............................................................................................................................................ 3
2-4. Operating Precautions............................................................................................................................ 3
2-5. Important information about explosion-proof ......................................................................................... 4
3. Product Components ...................................................................................................................................... 6
3-1. Main unit and standard accessories....................................................................................................... 6
3-2. Names and functions for each part ........................................................................................................ 7
4. How to Use ..................................................................................................................................................... 8
4-1. Before using the detector head .............................................................................................................. 8
4-2. Precautions for installation sites............................................................................................................. 8
4-3. Precautions for system designing .......................................................................................................... 9
4-4. How to install ........................................................................................................................................ 10
4-5. Grounding ............................................................................................................................................. 11
4-6. Wiring ................................................................................................................................................... 12
4-7. Compatible cables and terminal plate specifications ........................................................................... 12
4-8. System connection example ................................................................................................................ 13
5. How to Operate............................................................................................................................................. 15
5-1. Preparation for start-up ........................................................................................................................ 15
5-2. Basic operating procedures ................................................................................................................. 15
5-3. How to start the detector head (power-on) .......................................................................................... 16
5-4. Modes ................................................................................................................................................... 17
5-5. Description of operation (detection mode) ........................................................................................... 18
5-6. Description of operation (maintenance) ............................................................................................... 20
5-7. How to exit ............................................................................................................................................ 23
6. Maintenance ................................................................................................................................................. 24
6-1. Maintenance intervals and items.......................................................................................................... 24
6-2. Replacement parts ............................................................................................................................... 25
7. Storage, Relocation and Disposal ................................................................................................................ 26
7-1. Procedures to store the detector head or leave it for a long time ........................................................26
7-2. Procedures to relocate the detector head or use it again .................................................................... 26
7-3. Disposal of products ............................................................................................................................. 26
8. Troubleshooting ............................................................................................................................................ 27
9. Product Specifications .................................................................................................................................. 28
9-1. List of specifications ............................................................................................................................. 28
9-2. Detection principle ................................................................................................................................ 30
10. Definition of Terms ...................................................................................................................................... 30

1. Outline of the Product1-1. Preface

1

Outline of the Product1-1. Preface
Thank you for choosing our 2-wire gas detector head GD-F88Ai.
Please check that the model number of the product you purchased is included in the specifications on thismanual.
This manual explains how to use the detector head and its specifications. It contains information required
for using the detector head properly. Not only the first-time users but also the users who have already used
the product must read and understand the operating manual to enhance the knowledge and experience
before using the detector head.
When the detector head is used in combination with an indicator/alarm unit, read also the operating
manual of the indicator/alarm unit.

1-2. Purpose of use
 This product is a fixed type gas detector head which detects oxygen concentration in the air.
 When the detector head detects oxygen, it outputs a current according to the gas concentration.
The indicator/alarm unit indicates the gas concentration and triggers an alarm if a preset concentrationlevel is exceeded.
 The detector head is a safety unit, not an analyzer or densitometer which performs
quantitative/qualitative analysis/measurement.
Please fully understand the features of the detector head before using it, so that it can be used properly.
 The detector head outputs oxygen concentration in 4 to 20 mA.

1-3. Definition of DANGER, WARNING, CAUTION andNOTE
DANGER

This message indicates that improper handling may cause serious damage on life,
health or assets.
This message indicates that improper handling may cause serious damage on

WARNING health or assets.
CAUTION

This message indicates that improper handling may cause minor damage on
health or assets.

NOTE

This message indicates advice on handling.

-1-2. Important Notices on Safety

2-1. Danger cases

2

Important Notices on
Safety2-1. Danger cases
DANGER
This detector head employs the intrinsically safe explosion-proof structure (safety maintaining device
used separately); however, never attempt to detect a gas over the lower explosive limit (LEL).

2-2. Warning cases
WARNINGPower supply
Before turning on the detector head, always check that the voltage is properly applied.

Need of grounding circuit
Do not cut the grounding circuit inside or outside the detector head or disconnect the wire fromthe grounding terminal.
In both of the cases, the detector head will be in danger.

Defects in protective functions
When seeming defects are found in the protective functions, such as protective grounding, do notstart the detector head.
Before starting the detector head, check the protective functions for defects.

Grounding Zener Barrier
Never fail to perform A type grounding for Zener Barrier.



Operation in a gas
The detector head employs the intrinsically safe explosion-proof structure (safety maintaining
device used separately).
It can be used in a location where a combustible or explosive gas, or steam is present; however,it should be done carefully.
Consult RIKEN KEIKI before operating the detector head in such a location.

External connection
Before connecting the detector head to the external control circuit, securely connect it to aprotective grounding circuit.

-2-2. Important Notices on Safety

2-3. Precautions

WARNING

Handling of sensor
Do not disassemble the sensor unit because it contains electrolyte. If contact occurs, rinse thearea immediately with a large quantity of water.

Calibration
When performing calibration for the detector head, be careful of loose tubes, etc. to prevent
personnel from contacting gases.

Response to gas detection
When a gas is detected, it indicates a potentially dangerous situation. Take proper actions basedon your judgment.

2-3. Precautions
CAUTION

Do not use a transceiver near the detector head.
Radio wave from a transceiver etc. near the detector head or its cables may disturb indication
reading. If a transceiver or other radio wave transmitting device is used, it must be used in a place
where it disturbs nothing.



To restart the the detector head, wait for five seconds or more before doing it.
Restarting the detector head within five seconds may cause errors.



Careful consideration should be given to instrumentation to maintain safety even when a trouble
like disconnection of power/signal cable or unexpected malfunction or failure occurs.

This is an electrical appliance. Be careful that it may be affected, in rare cases, by power supply
noises, static electricity, and electromagnetic noises. Before using the detector head in anenvironment with such noises, provide for protective measures against them.

2-4. Operating Precautions
This product is a gas detector that detects oxygen in the air and outputs gas concentration signals.
The detector head is a safety unit, not an analyzer or densitometer which performs quantitative/qualitative
analysis/measurement for gases.
Please fully understand the following points before using it, so that it can be used properly.

1.

The readings of the detector head fluctuate slightly in response to changes in the air pressure.
In particular, be careful of alarm activation when a low air pressure is brought in by typhoon. In addition, it
may be fluctuated by environmental (temperature, humidity etc.) changes in the installation site.

2.

This is a safety unit, not a control unit.
Use the analog signal output of the detector head for an indicator or external recorder.
If these outputs are used to control other units, we shall not be responsible for any malfunctions.

3.

For maintenance of the detector head, it must go through a regular maintenance, including replacement
and adjustment of the regular replacement parts as specified in the operating manual. In addition, because
this is a safety unit, it is recommended that regular maintenance and span adjustment be performed every
six months.

-3-2. Important Notices on Safety

2-5. Important information about explosion-proof

Important information about explosion-proof (continued) Power supply
Never fail to use the following safety maintaining device (barrier) to maintain explosion-proof
performance.
Ratings to maintain safety
Intrinsically safe circuit maximum voltage (Uo)Intrinsically safe circuit maximum current (Io)Intrinsically safe circuit maximum power (Po): 28 V: 93 mA: 0. 65 W

Performance classification and group
Performance classification:iaGroup:
IIC
Relations between the intrinsically safe circuit allowable inductance (Lo) and intrinsically safe circuit
external wire inductance (Lc) and between the intrinsically safe circuit allowable capacitance (Co) andintrinsically safe circuit external wire capacitance (Cc)
Intrinsically safe circuit allowable inductance (Lo)= (Lc) or more
Intrinsically safe circuit allowable capacitance (Co) = 586 pF + (Cc) or more
 Wiring
Determine the cable type to use and laying distance in consideration of the above parameters tomaintain explosion-proof performance.
Perform wiring so that a current or voltage that disturbs intrinsically safe explosion-proof performanceof the intrinsically safe circuit is not induced to the circuit due to electromagnetic or electrostaticinduction.
 Battery
The detector head contains a battery for sensor backup. Observe the followings to maintainexplosion-proof performance.
<Usable battery>Type:
AAA alkaline dry battery
Model:
LR03
Nominal voltage: 1. 5 V<Battery Replacement>
Turn off the power of the detector head before replacing the battery.
Never fail to use the dedicated battery storage case.
 Grounding
Never fail to ground the detector head (D type grounding).
 Others
Confirm that no combustible gas is present around before opening the door of the unit.
Never disassemble or modify the unit.
Manufacturer: RIKEN KEIKI Co., Ltd.
2-7-6 Azusawa, Itabashi-ku, Tokyo, 174-8744 Japan
www.rikenkeiki.co.jp*1: The temperature range to maintain explosion-proof performance
The temperature range to maintain gas detection performance is 0 to +40°C. (See
Specifications)-5-4. How to Use

4-1. Before using the detector head4

How to Use
4-1. Before using the detector headNot only the first-time users but also the users who have already used the detector head never fail to follow
the operating precautions.
Ignoring the precautions may damage the detector head, resulting in inaccurate gas detection.

4-2. Precautions for installation sites
CAUTION This is a precision device. Because the detector head may not provide the specified performancein some places (environments), check the environment in the installation point, and then takeappropriate actions if necessary.
 Because the detector head plays an important role for safety and disaster prevention, as many
units of the detector head as needed must be installed in appropriate points.
Because points where gases leak and remain easily are different depending on the types ofgases and the working areas, please decide carefully on installation points and the number ofunits to be installed.
Do not install the detector in a place with vibrations or shocks.
The detector head consists of sensitive electronic parts. The detector must be installed in a stable place
without vibrations or shocks and it cannot drop.
Do not install the detector head in a place exposed to direct sunlight or sudden changes in the temperature.
When selecting installation points, avoid a place where it is exposed to direct sunlight or radiant heat
(infrared rays emitted from a high-temperature object), and where the temperature changes suddenly.
Condensation may be formed inside the detector head, or the detector head cannot adjust to suddenchanges in the temperature.
Keep the detector head (and its cables) away from noise source devices.
When selecting installation points, avoid a place where high-frequency/high-voltage devices exist.
 Do not place the detector head next to a noise source device.
 Do not run cables in parallel or close to each other.
Do not install the detector head in a place where maintenance of the detector cannot be performed or wherehandling the detector involves dangers.
Regular maintenance of the detector head must be performed.
Do not install the detector head in a place where the machinery must be stopped when maintenance isperformed in its inside, where parts of the machinery must be removed to perform maintenance, or where
the detector head cannot be removed because tubes or racks, etc. prevent access to it.
Do not install the detector head in a place where maintenance involves dangers, for example, near a highvoltage cable.

-8-4. How to Use

4-3. Precautions for system designing

Do not install the detector head in machinery which is not properly grounded.
Before installing the detector head in machinery, the machinery must be grounded properly.
Do not install the detector head in a place where interference gases exist around it.
The detector head must not be installed in a place where interference gases exist around it.

4-3. Precautions for system designing
CAUTION
An unstable power supply and noise may cause malfunctions or false alarms.
The descriptions in this section must be reflected on the designing of a system using the detector
head.
Using a stable power supply
The external output and alarm contact of the detector head may be activated when the power is turned on,when momentary blackout occurs, or while the system is being stabilized. In such cases, use a UPS(uninterruptible power system), or take appropriate actions on the receiving side.
The detector head must be provided with the following power supply.
Power supply
voltage

15 - 27 VDC (terminal voltage of the main unit)

Allowed time of
momentary blackout

Approx. 1 msec. (To recover from themomentary blackout for 1 msec. or
more, restart the detector head.)

OthersDo not use it with a power supply oflarge power load or high-frequency
noise.

Example of actions
To ensure continuous operation andactivation, install a UPS, etc. outside
the detector head.
Example of actions
Use a line filter, etc. to avoid the noise
source if necessary.

Heat radiation designing
When the alarm system is installed in a closed instrumentation panel or the like, attach ventilation fansabove and below the panel.
Introducing protective measures against lightning
If cables are installed outside the factory/plant, or if internal cables are installed in the same duct as thecables coming from outside the factory/plant, "lightning" will cause problems. Because lightning acts as alarge emission source while cables act as a receiving antenna, devices connected to the cables may bedamaged.
Lightning cannot be prevented. Cables installed in a metal conduit or under the ground cannot becompletely protected from inductive lightning surge caused by lightning. Although complete elimination ofdisasters caused by lightning is impossible, the following protective measures can be taken.

Protection against
lightning

Grounding

Take appropriate measures in accordance with the importance of the facilities andthe environment.
 Provide protection by a lightning arrester (cable arrester).
(Although inductive lightning surge can be transmitted through the cable, itis prevented by installing a lightning arrester before the field devices andcentral processing equipment. For information on how to use a lightning
arrester, please contact the manufacturer.)
In addition to lightning, there are more sources of surge noise. To protect units
from these noise sources, the units must be grounded.

* The lightning arrester has a circuit to remove a surge voltage which damages field devices, so thatsignals may be attenuated.
Before installing a lightning arrester, verify that it works properly.

-9-4. How to Use

4-6. Wiring

4-6. Wiring
CAUTION Be careful not to damage the internal electronic circuit when wiring.
 The connected cables must not be installed together with the motor power cables, etc.
 When stranded wires are used, prevent wires from contacting each other.

4-7. Compatible cables and terminal plate
specifications<Recommended Cables>
Use CVVS 1. 25 sq 2-core single or stranded wire.
<Specifications of Terminal Plate> Rated voltage: 250 VAC
 Rated current: 20 A

Groundingterminal+-

Power supply and output signal
4 - 20 mA<Supply Voltage>
The supply voltage is normally 24 VDC.
However, the voltage at the terminal plate of the detector head becomes lower than the source voltage,
depending on the connected safety maintaining device (barrier), type and length of the cable used.
It may also vary with the signal current value (4 to 20 mA).
When wiring the detector head, check the following to make sure that the voltage at the terminal plate isappropriate.
The detector head provides stable operation within the power voltage range of 15 to 27 VDC.
< Withstand voltage performance>
The detector has a withstand voltage performance of 500V AC for 1 minute between the power supply andoutput signal terminals and the earth (between containers).

- 12 -

5. How to Operate

5-1. Preparation for start-up

5

How to Operate
5-1. Preparation for start-up
Before connecting a power supply, read and understand the following precautions. Ignoring theseprecautions may cause an electric shock or damage the unit.






Check that the detector head is installed properly.
Check that the detector head is grounded.
Check that the external wiring is done properly.
Check that the power supply voltage meets the specification and rating.
The external output may be fluctuated during adjustment. Take an appropriate measure to avoid theinfluence on the gas monitoring system.
 Make sure to use a fuse with the specified ratings to prevent fire.

5-2. Basic operating procedures
Normally, the detection mode is used for normal operations. (The detection mode is activated after the
power is turned on.)Preparation for start-up

Power On

Initial clear (approx. 25 seconds)

Detection mode

MODE switch (hold down for approx. 3 seconds)

Maintenance mode
 Fresh air adjustment mode Regular maintenance mode

- 15 -

5. How to Operate

5-4. Modes

5-4. Modes
Details on each mode are provided as follows.

CAUTION Do not change the settings if not necessary. Changing the settings without understanding thespecifications may cause malfunctions.

Mode
Detection Mode

Maintenancemode(User)

Item-

LED
displayGas
concentration

Details
Normal state

ROM/SUM display

1-0

Zero adjustment
Setting display
Regular maintenancemode switching

1-1
1-2

Display the program version and others.
This is not typically used by the user.
Perform zero adjustment.
Display various setting values.

1-3

Switch to the regular maintenance mode.

Test mode

2-0

Zero adjustment
Span (fresh air)adjustment----------

2-1

Perform various tests.
2-0-0 Gas Test
2-0-1 Alarm Test
2-0-2 Fault Test
2-0-3 LCD Test
2-0-4 ---------Perform zero adjustment.

2-2

Perform span (fresh air) adjustment.

2-3

Environmental setting

2-4

Display

2-5---------Used for various environmental settings.
2-4-0---------2-4-1 INHIBIT Setting
2-4-2 Alarm Setpoint Setting
2-4-3 Alarm Delay Time Setting
2-4-4 Alarm Pattern Setting
2-4-5 Zero Suppression Type Setting
2-4-6 Zero Suppression Value Setting
2-4-7 ---------2-4-8 ---------2-4-9 ---------2-4-A Maintenance Mode External Output Setting
2-4-B External Output Adjustment
2-4-C Alarm Test External Output Setting
2-4-D Sensor Operation Start Setting
2-4-E ---------2-4-F ---------2-4-G Alarm Limiter Setting
2-4-J Sensitivity Correction Setting
2-4-K Date/Time Setting
2-4-M Air Pressure Correction
2-4-N Fault External Output Setting
Display various electrical settings.
This is not typically used by the user.

Maintenancemode(Regularmaintenance)

Switch to factorymode
Switch to user mode

2-6

Not used.

2-7

Return to the user mode.

- 17 -

5. How to Operate

5-7. How to exit

5-7. How to exit
To turn off the detector head, turn off the power switch located on the left side of the power terminal plate.
Then, turn off the power supply (24 VDC) to the detector head.

WARNING
Decide whether the power can be turned off by checking the operation of the devices connected tothe external output of the detector head head before turning it off.

- 23 -

6. Maintenance

6-1. Maintenance intervals and items

6

MaintenanceThe detector head is an important instrument for the purpose of safety.
To maintain the performance of the detector head and improve the reliability of safety, perform a regular
maintenance.
Continuing to use the detector head without performing maintenance will compromise the sensitivity of the gas
sensor, thus resulting in inaccurate detection.

6-1. Maintenance intervals and items
 Daily maintenance: Perform maintenance before beginning to work.
 Monthly maintenance: Perform maintenance on the alarm circuit (alarm test) once a month.
 Regular maintenance: Perform maintenance once or more for every six months to maintain theperformance as a safety unit.
Maintenance item

Maintenance content

Status display check

Check that the status indicates normal
measurement state.
Check that a gas to be detected is not present
around the detector head and that the reading
indicates a normal value.
Inspects the alarm circuit by using the alarm test
function.
Perform the span adjustment by using thecalibration gas.
Check the gas alarm by using the calibrationgas.

Gas concentration
display
Alarm test*
Span adjustment
Gas alarm check

Daily
Monthly
Regularmaintenance maintenance maintenance
○

○

○

○

○

○

－

○

○

－

-

○

－

-

○

* Check and adjustment are performed at the indicator/alarm unit side. See the operating manual of theindicator/alarm unit for details.
<About Maintenance Services> We provide services on regular maintenance including span adjustment, other adjustments andmaintenance.
To make the calibration gas, dedicated tools, such as a gas cylinder of the specified concentration andgas sampling bag must be used.
Our qualified service engineers have expertise, knowledge and other information on the dedicated tools
used for services, along with other products. To maintain the safety operation of the detector head,please use our maintenance service.
 Typical maintenance services are listed as follows. Please contact RIKEN KEIKI for more information.

- 24 -

6. Maintenance

6-2. Replacement parts

Main services
Power supply check::

Checks the power supply voltage.
Checks that the status indicates normal measurement state.

Concentration display
check*
Alarm test*:

Verifies that the concentration display value is zero by using the zero gas.
Performs zero adjustment if the display is incorrect.

:

Span adjustment
Cleaning and repair of
the unit(visual diagnosis)
Unit operation check
Replacement ofconsumable parts::

Inspects the alarm circuit by using the alarm test function.
 Checks the alarm lamps. (Checks the activation.) Checks the external alarm. (Checks the activation of the external alarm,such as a buzzer.)
Performs the span adjustment by using the calibration gas.
Checks dust or damage on the surface, cover or internal parts of the unit, andcleans or repairs such parts as needed.
Replaces parts which are cracked or damaged.
Uses the keys to check the operation of functions, parameters, etc.
Replaces consumable parts, such as a sensor and filter.

Status display check::* Check and adjustment are performed at the indicator/alarm unit side.

6-2. Replacement parts<Replacement of Gas Sensor>
Our service engineers need to replace and adjust the sensor. Please contact RIKEN KEIKI.

NOTE
 If adjustment to the standard gas concentration value fails even with the maximum sensitivity, it
indicates that the gas sensor has come to the end of its life. The gas sensor needs to be replaced.
 After replacing the gas sensor, electrical adjustment and calibration using the standard gas arenecessary.

- 25 -

7. Storage, Relocation and Disposal

7-1. Procedures to store the detector head or leave it for a long time7

Storage, Relocation and
Disposal
7-1. Procedures to store the detector head or leave it
for a long time
The detector head must be stored under the following environmental conditions.
 In a dark place under the normal temperature and humidity away from direct sunlight In a place where gases, solvents or vapors are not present

7-2. Procedures to relocate the detector head or use it
again
When the detector head is relocated, select a new place in accordance with "4-2. Precautions for
installation sites" and "4-4. How to install".
For information on wiring work, see "4-6. Wiring" and "4-7. Compatible cables and terminal plate
specifications". The unpowered time must be minimized when the detector head is relocated.

CAUTION
When using a relocated or stopped/stored detector head again, never fail to perform a calibration.
For information on readjustment including a calibration,please contact RIKEN KEIKI.

7-3. Disposal of products
When the detector head is disposed of, it must be treated properly as an industrial waste in accordancewith the local regulations.

WARNING
Do not disassemble the sensor because it contains electrolyte.
Electrolyte may cause severe skin burns if it contacts skin, while it may cause blindness if it contacts
eyes.
If electrolyte is adhered on your clothes, that part on your clothes is discolored or its material isdecomposed.
If contact occurs, rinse the area immediately with a large quantity of water.

- 26 -

8. Troubleshooting

8

Troubleshooting
The Troubleshooting does not explain the causes of all the malfunctions which occur on the unit. This
simply helps to find the causes of malfunctions which frequently occur. If the detector head shows asymptom which is not explained in this manual, or still has malfunctions even though remedial actions aretaken, please contact RIKEN KEIKI.
(1) Nothing is displayed on LCD (power cannot be turned on).
<Causes and Actions> Check that the power voltage indicated at the terminal is appropriate.
If it is lower than the source voltage significantly, there may be a problem in the connected safety
maintaining device, cable or cable connection.
(2) Abnormal operations<Causes and Actions> A sudden surge noise can be the cause. To recover, turn OFF the detector head power and thenturn it ON again to restart.
 If such a symptom is observed frequently, take appropriate measures to eliminate the noise.
(3) Span adjustment impossible<Causes and Actions> Check that the calibration gas concentration is appropriate.
Use the proper calibration gas.
 The sensor sensitivity may be deteriorated.
The sensor needs to be replaced.
(4) Fault indication appears.
1. System abnormality "E-00"<Causes and Actions> An abnormality occurs in the internal part of the detector.
Contact RIKEN KEIKI.
2. Sensor connection abnormality "E-01"<Causes and Actions> The sensor has not been connected, or poor connection of the connector occurs.
 Check that the sensor is attached and that the sensor is attached securely to the connector. If thesituation does not improve, contact RIKEN KEIKI.

- 27 -

9. Product Specifications

9

Product Specifications
9-1. List of specifications＜Oxygen Deficiency Alarm) SPECIFICATION＞
Model
Detection principle
Gas to be detected
Concentration display
Detection range
Detection method
Alarm preset point
Indicate accuracy

GD-F88Ai
Galvanic cell method
O27-segment LCD (4 digits)
0～25vol%
Diffusion type18vol%(1st<L>)【Standard】
18vol%(2nd<LL>)【Standard】
Within ±0.7vol%(under an identical condition)

Response time

Within 30sec(T90)(under an identical condition)

Alarm-delay time
(under an identical condition)

Gas alarm typeGas alarm indication
Gas alarm action
Trouble alarm･Self diagnosis
Trouble alarm indication
Trouble alarm action
Transmission method
Transmission specifications
Communication schemePower supply
Power consumption
Transmission cable
Transmission distance
Safety maintaining device
Operating temperature
Operating humidity
Structure
Explosion-proof structure
Explosion-proof class
External dimensions
WeightBy anoxia alarm(Alarm setpoint value:18vol%), Within
5sec(when introducing 10～11vol% gas)
Two-step alarm (L-LL)
Alarm message(AL1/AL2)
Latching or non latching
System failure/Sensor failure
Content display
Non latching
2-wire analog transmission + digital transmission (HART
Communication)
4-20mADC (load resistance: 300Ω or less)
HART 7
24VDC±10%
Approx. 0.6W
Shielded cable of CVVS, etc. (1.25mm2) - 2-core
Up to 1km with CVVS 1.25 mm2 (up to 600m between the detector
head and Zener Barrier)
Zener Barrier (MTL7728ac/MTL7728+/MTL7728-) or
insulating barrier (MTL5541/RN221N-J1/KFD2-STC4-Ex1)-10 - +40℃ (non-rapidly-vary)Less than 95%RH (non-condensing)
Wall mounted type
Intrinsically safe explosion-proof structure, with safety
maintaining device (barrier) used
Ex ia ⅡC T4 Ga
Approx. 100(W)x241(H)x48(D)mm (projection portions excluded)
Approx. 1.0kg- 28 -

9. Product Specifications
Material
Paint
Outer color

9-1. List of specifications
SECC or SS304
Bake-coated with melamine
Munsell 2.5Y9/2＜Gas minitoring SPECIFICATION＞
Model
Detection principle
Gas to be detected
Concentration display
Detection range
Detection method
Alarm preset point
Indicate accuracy(under an identical condition)

Response time

GD-F88Ai
Galvanic cell method
O27-segment LCD (4 digits)
0～5vol%/0～10vol%/0～25vol%
Diffusion type
Depend on measuring range
Within ±0.7vol%(below 25vol% range)
Within ±3vol%(above 25vol% range)
Within 30sec(T90)(under an identical condition)

Gas alarm typeGas alarm indication
Gas alarm action
Trouble alarm･Self diagnosis
Trouble alarm indication
Trouble alarm action
Transmission method
Transmission specifications
Communication schemePower supply
Power consumption
Transmission cable
Transmission distance
Safety maintaining device
Operating temperature
Operating humidity
Structure
Explosion-proof structure
Explosion-proof class
External dimensions
WeightMaterial
Paint
Outer color

Two-step alarm (H-HH, L-H, and L-LL)
Alarm message(AL1/AL2)
Latching or non latching
System failure/Sensor failure
Content display
Non latching
2-wire analog transmission + digital transmission (HART
Communication)
4-20mADC (load resistance: 300Ω or less)
HART 7
24VDC±10%
Approx. 0.6W
Shielded cable of CVVS, etc. (1.25mm2) - 2-core
Up to 1km with CVVS 1.25 mm2 (up to 600m between the detector
head and Zener Barrier)
Zener Barrier (MTL7728ac/MTL7728+/MTL7728-) or
insulating barrier (MTL5541/RN221N-J1/KFD2-STC4-Ex1)-10 - 40℃ (non-rapidly-vary)Less than 95%RH (non-condensing)
Wall mounted type
Intrinsically safe explosion-proof structure, with safety
maintaining device (barrier) used
Ex ia ⅡC T4 Ga
Approx. 100(W)x241(H)x48(D)mm (projection portions excluded)
Approx. 1.0kg
SECC or SS304
Bake-coated with melamine
Munsell 2.5Y9/2- 29 -