General Monitors S104 User manual

The information and technical data disclosed
in this document may be used and
disseminated only for the purposes and to
the extent specifically authorized in writing
by General Monitors.
Instruction Manual 04/97
General Monitors reserves the right to
change published specifications and designs
without prior notice.
Part No. MANS104
Revision J/04-97
Model S104
Combustible Gas
Enhanced Smart Sensor
GENERAL MONITORS
Model S104

Warranty
General Monitors warrants the Model S104
to be free from defects in workmanship or
material under normal use and service within
two (2) years from the date of shipment. Gen-
eral Monitors will repair or replace without
charge any such defective equipment to be
found defective during the warranty period.
Full determination of the nature of, and re-
sponsibility for, defective or damaged equip-
ment will be made by General Monitors’
personnel. Defective or damaged equipment
must be shipped prepaid to General Monitors’
plant or representative from which shipment
was made. In all cases this warranty is lim-
ited to the cost of the equipment supplied by
General Monitors. The customer will assume
all liability for the misuse of this equipment
by its employees or other personnel.
All warranties are contingent upon proper use
in the application for which the product was
intended and do not cover products which
have been modified or repaired without Gen-
eral Monitors’ approval or which have been
subjected to neglect, accident, improper in-
stallation or application, or on which the
original identification marks have been re-
moved or altered. Except for the express war-
ranty stated above, General Monitors
disclaims all warranties with regard to the
products sold, including all implied warranties
of merchantability and fitness and the express
warranties stated herein are in lieu of all obli-
gations or liabilities on the part of General
Monitors for damages including, but not lim-
ited to, consequential damages arising out
of/or in connection with the use or perform-
ance of the product.
i
Warning
The Model S104 Combustible Gas Enhanced
Smart Sensor Assembly contains components
which can be damaged by static electricity.
Special care must be taken when wiring the
system to ensure that only the connection
points are touched.
GENERAL MONITORS
Model S104

Table Contents
Warranty
Warning - Electrostatic Damage
1.0 Introduction
1.1 General Description
1.2 Features and Benefits
1.3 Applications
2.0 Sensor Assembly
2.1 Sensor Signal Processing
2.2 Power Supply
2.3 Control Electronics
3.0 Installation
3.1 Receipt of Equipment
3.2 Sensor Location Considerations
3.3 Installation Instructions
3.4 Terminal Connections
3.5 Applying Power
3.6 Maintaining the X/P Integrity
4.0 Operation
4.1 Calibration
4.2 Digital Display Codes
4.3 Fault Codes & Their Remedies
5.0 Appendix
5.1 Specifications
5.1.1 System Specifications
5.1.2 Electrical Specifications
5.1.3 Mechanical Specifications
5.1.4 Environmental Specifications
5.2 Engineering Documentation
5.2.1 Termination & Outline Drawings
5.2.2 Termination & Outline Drawing - CE Marked Unit
5.3 Ordering Information
5.3.1 Configuration Codes
5.3.2 Spare Parts and Accessories
5.4 FMRC Approval
Page Number
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GENERAL MONITORS
Model S104

Table of Figures
Figure 1 Combustible Gas Sensor Diagram
Figure 2 Input Signal Circuit Flow Diagram
Figure 3 Power Supply Circuit Flow Diagram
Figure 4 Control Electronics Flow Diagram
Figure 5 Overall and Mounting Dimensions
Figure 6 Conduit, Drain Loop, and Seal Drawing
Figure 7 Terminal Connections
Figure 8 Terminal Block Operation Drawing
Figure 9 Wire Strip Length Diagram
Figure 10 0-20mA Output Signal Connections
Figure 11 Input Power Connections
Figure 12 GMI Logo and Display Window Drawing
Figure 13 Display Diagram, Automatic Calibration
Figure 14 Display Diagram, Calibration in Progress
Figure 15 Display Diagram, Calibration Complete
Figure 16 Display Diagram, Zero Indication
Figure 17 LED Flashing Sequences
Figure 18 Display Diagram, Test Gas Mode
Figure 19 Termination Drawing - Standard Unit
Figure 20 Outline & Dimensional Drawing
Figure 21 Termination Drawing - CE Marked Unit
Page Number
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iii
GENERAL MONITORS
Model S104

1.0 Introduction
1.1 General Description
The Model S104 Enhanced Smart Sensor as-
sembly is used to detect combustible gases.
The microprocessor based electronics, which
are contained within an explosion proof hous-
ing, process sensor input at the sensor site. An
optional digital display provides indications
and display codes that can be viewed through
a window in the cover. An analog output sig-
nal (4-20mA) provides remote and/or discrete
indications of the sensor’s operation. The
Model S104 Enhanced Smart Sensor Assem-
bly is rated explosion proof for use in Class I,
Division 1, Group B, C, and D hazardous ar-
eas.
1.2 Features and Benefits
Microprocessor Based Electronics: monitors
9 individual fault conditions, processing input
signals from the sensor and providing outputs
in the form of LED flashing sequences, dis-
play codes, and an analog output signal.
One Person Calibration: initiate the calibra-
tion sequence with a magnet, apply the gas,
and wait for the LED switch or optional dis-
play to indicate that the unit has completed the
calibration. No tools or adjustments are re-
quired.
2 Digit Display: (optional) indicates gas con-
centrations, fault codes, and calibration cues.
4 to 20 mA Output: transmits fault, calibra-
tion, and gas concentrations to a remote dis-
play, computer or other device.
1.3 Applications
This is a partial listing of applications.
lDrilling and Production Platforms
lFuel Loading Facilities
lCompressor Stations
lOil Well Logging
lLNG/LPG Processing and Storage
lWaste Water Treatment
lGas Turbines
lSolvent Vapors
lHydrogen Storage
1
GENERAL MONITORS
Model S104

2.0 Sensor Assembly
2.1 Sensor Signal Processing
General Monitors uses a low temperature
catalytic bead to detect the presence of com-
bustible gases. Combustible gases are found
in many gases and vapors. The catalytic bead
converts the combustible gas to heat. A
change in heat is converted to a change in re-
sistance.
By taking a matched pair of catalytic beads
and coating one so that it does not respond to
the presence of combustible gases, we can
compare the change in resistance between the
two beads. The bead that is coated is called
the reference bead and the other is called the
active bead (figure 1). Environmental factors
can also influence the temperature of the cata-
lytic beads. Because the beads are a matched
pair, they will respond to changes in ambient
temperature, humidity, and pressure equally.
figure 1
By connecting one end of each catalytic bead
together, a series circuit is formed. This cir-
cuit is supplied with a constant voltage. The
voltage drop across each of the beads will be
identical in the absence of combustible gases.
As combustible material is converted to heat,
the resistance of the active bead increases,
causing the voltage drop across each bead to
be different. This difference is proportional to
the amount of combustible gas that is present.
The voltage from the sensor is amplified and
fed to an Analog to Digital (A/D) converter
and then made available to the microprocessor
(figure 2).
figure 2
The baseline and the gain for the amplifier are
determined by digital potentiometers. They
are adjusted by the microprocessor during
calibration.
3
GENERAL MONITORS
Model S104

Sensor Assembly
2.2 Power Supply
The Model S104 operates from a +24 VDC
(nominal) input. This unregulated source is
fed to a converter board that produces volt-
ages (see figure 3). These signals are the
source for operating all of the circuitry on the
control and the display boards, and supplying
the sensor with power. Terminal connections
inside of the housing have been provided for
accepting the input power.
2.3 Control Electronics
The control electronics are centered around an
eight bit microprocessor (figure 4). The Sen-
sor Signal, the CAL Switch, the Non-Volatile
Memory (NOVRAM), and certain Fault con-
ditions are monitored as inputs. By process-
ing these inputs, the following outputs are
generated: 4-20mA Output Signal, Digital
Display Indications, and Calibration Values
(NOVRAM). As the microprocessor (MPU)
receives and processes the inputs, it deter-
mines what value is output to the display, and
the 4-20mA current generator. When the
CAL Switch is activated, the MPU allows the
user to choose between the Calibration or the
Test Gas Modes. While the unit is in one of
these modes, the MPU will fix the 0-20mA
output signal to 1.5mA (0mA signal is op-
tional for the calibration mode only).
Calibration Mode: When the unit is placed
in this mode, the MPU accepts a ZERO value
and waits for the signal from the sensor to in-
crease and then stabilize. It accepts this final
value as the SPAN value. These values are
stored in NOVRAM and are used to adjust
the digital potentiometers associated with the
Input Amplifier.
figure 3
Test Gas Mode: In this mode, the MPU will
output the gas concentration to the display
while fixing the analog output at 1.5mA.
When the gas concentration drops below 10%
LEL, the unit will return to normal operation.
The purpose of this mode is to check the re-
sponse of the unit to a known level of gas and
determine if calibration is necessary.
figure 4
4GENERAL MONITORS
Model S104

3.0 Installation
3.1 Receipt of Equipment
All equipment shipped by General Monitors is
packed in shock absorbing containers which
provide considerable protection against physi-
cal damage. The contents should be carefully
removed and checked against the packing
slip. If any damage has occurred or if there is
any discrepancy in the order, notify General
Monitors as soon as possible. All subsequent
correspondence with General Monitors must
specify the equipment part and serial num-
bers.
Each Model S104 is completely checked by
the factory. However, a complete check-out
is necessary upon initial installation and start
up to ensure system integrity.
3.2 Sensor Location Considerations
There are no standard rules for sensor place-
ment since the optimum sensor location is dif-
ferent for each application. The customer
must evaluate conditions at the facility to
make this determination. Generally, the
Model S104 Enhanced Smart Sensor should
be easily accessible for calibration checks.
The sensor assembly should be mounted
pointing down to prevent water build-up on
the sensor head. The sensor assembly should
not be placed where it may be coated by con-
taminating substances. Although the Model
S104 is RFI resistant, it should not be
mounted in close proximity to radio transmit-
ters or similar equipment.
lLocate the Model S104 where prevailing
air currents contain the maximum
concentration of gas.
lLocate the Model S104 near possible
sources of gas leaks.
lObserve the Model S104’s temperature
specification and locate the unit away
from concentrated sources of heat.
lSensor Assemblies should be mounted in
an area that is as free from wind, dust,
water, shock, and vibration as possible.
See Appendix, section 5.1.4 for the
environmental specifications of the unit.
Sensors may be adversely affected by pro-
longed exposure to certain materials. Loss of
sensitivity or corrosion may be gradual if such
materials are present in low concentrations, or
it may be rapid at high concentrations. The
more important materials adversely affecting
sensors are:
lProlonged presence of Hydrogen Sulfide
(H2S) gas
lSilicones (often contained in greases and
aerosols). Silicones do not chemically
attack the sensor, they coat it and reduce
or inhibit its response to the presence of
combustible gas.
lHalides . . . compounds containing
Fluorine, Chlorine, Bromine, and Iodine
lHeavy metals, (e.g. Tetraethyl Lead)
The presence of poisons and contaminants in
an area does not necessarily preclude the use
of a Model S104 Enhanced Smart Sensor. The
feasibility of using a sensor in such areas must
be determined by an analysis of the specific
factors in each application and General Moni-
tors should be consulted before attempting
any such installation.
5
GENERAL MONITORS
Model S104

Installation
Sensor Location Considerations (continued)
Sensors used in these areas usually require
more frequent calibration checks than normal,
and typically have a shorter life. In many
such applications the normal two year war-
ranty would not apply.
CAUTION:
General Monitors discourages the painting
of sensor assemblies. If the sensor head is
painted over, the gas will not be able to dif-
fuse into the sensor. If the assembly cover
is painted over, the digital display cannot
be read.
Remoting the Sensor from the Electronics:
If it is necessary to remotely mount the sensor
from the electronics and the housing, the
maximum distance can be no greater than 100
feet, using 14 AWG wire. Sensors that are re-
motely placed must be contained in a sensor
housing (GMI P/N 10252) and the cable run
must be contained in a conduit running from
the sensor housing to the electronics. See Ap-
pendix, section 5.4.
3.3 Installation Instructions
The overall and mounting dimensions for the
Model S104 (figures 5 & 20) should be used
when making installation determinations. A
complete list of the mechanical specifications
can be found in the Appendix (section 5.1.3).
To prevent possible corrosion due to moisture
or condensation, it is recommended that the
conduit connected to the Model S104 housing
be sealed or contain a drain loop (figure 6).
Each conduit run from a hazardous location to
a non-hazardous location should be sealed so
that gases, vapors, and/or flames can not pass
beyond the seal. The purpose of seals in a
Class I hazardous location is to prevent the
passage of gases, vapors, or flames from one
electrical installation to another through the
conduit system. However, it is not required to
add a seal to the Model S104 housing to
maintain its explosion proof integrity. Spe-
cific information on Class I location seals and
drainage can be found in the National Electric
Code handbook, Article 501-5.
6
figure 5
GENERAL MONITORS
Model S104

Installation
Installation Instructions (continued)
NOTE:Acetic acid will cause damage to
metal components, metal hardware, ce-
ramic IC’s, etc. If damage results from the
use of a sealant that outgases acetic acid
(RTV silicone), the warranty will be void.
Once correctly installed, the Model S104 re-
quires little or no maintenance other than peri-
odic calibration checks to ensure system
integrity. General Monitors recommends that
a schedule be established and followed.
NOTE:The system’s full two year war-
ranty will be voided if customer personnel
or third parties damage the system during
repair attempts.
Sensor heads exposed to the elements may re-
quire the accessory mounting threads to be lu-
bricated. Grease must not be used. As an
alternate, PTFE (teflon) tape may be used on
threads that do not contact the sensor hous-
ing.
The removal of particulate matter from sensor
accessories may be done through the use of an
appropriate halogen-free solvent. Water or
ethanol are examples of suitable solvents. The
accessories should be thoroughly dried, with
compressed air if necessary, before refitting to
the sensor body.
General Monitors recommends that the com-
plete system, including all alarm circuitry, be
tested at least annually. Some typical items to
check during maintenance examinations are:
lThe sensor mounting, to see it is secure.
lThe sensor screen, to see it is clear of
water, oil, dust or paint which might clog
it.
lThe cable connections for tightness and
possible damage.
lAll sensor placements, to see that they are
up to date with the layout of the plant
(e.g. modifications to the plant).
lThe complete system, to see it has a back
up supply for the full prescribed time.
3.4 Terminal Connections
The terminal blocks (TB) are located inside of
the housing and can by accessed by removing
the cover (figure 7, CE Mark units see figure
21). TB2 contains the three sensor connec-
tions, White (W), Black (B), and Red (R).
figure 7
figure 6
GENERAL MONITORS
Model S104
7

Installation
Terminal Connections (continued)
TB1 contains the connections for Power, Re-
mote Functions, and Output Signal (see figure
7, CE Mark units see figure 21).
TB1 position Function
1 4-20mA Output
2 Calibration Switch
3 Calibration Switch
4 LED
5 LED
6 Common (Ground)
7 +24VDC Power
NOTE:Contact with PCB components
should be avoided to prevent damage by
static electricity. All wire connections are
made to the Terminal Blocks.
It is recommended that three wire (red, black,
white) shielded cable be used for making
power and output signal connections on the
Model S104. The terminal block accepts 16
AWG to 22 AWG stranded or solid wire.
Each wire should be stripped before wiring
the Model S104 Combustible Gas Enhanced
Smart Sensor. To connect wiring to the ter-
minal block, insert a screw driver into the or-
ange tab and press down (figure 8), opening
the terminal.
figure 8
Insert the wire into the terminal and release
the orange tab, clamping the wire in the termi-
nal. Check the connection by GENTLY tug-
ging the wire to ensure it is locked in.
figure 9
NOTE:14 AWG wire can be used if it is
carefully stripped (figure 9).
A 4 to 20mA output signal is provided by the
Model S104 Combustible Gas Enhanced
Smart Sensor and can be sent up to 9000 feet
(2740 meters) to a General Monitors read-
out/relay display module, industrial analog to
digital converter, computer based monitor,
PLC, DCS, etc. The 4 to 20mA signal pro-
vides for control room or other locations re-
mote to the Model S104 to display indications
of operation and alarm conditions.
To connect the 4 to 20mA output signal with
another unit, connect the white wire into TB1,
position 1 (CE Mark units - TB3, position 1),
labeled 4-20 mA OUT. For making output
signal connections to display devices, refer to
the specific manual for that device (figure 10).
figure 10
GENERAL MONITORS
Model S104
8

Installation
Terminal Connections (continued)
If a device other than a General Monitors
readout/relay display module is being used,
the commons, COM, of both systems must be
connected together. See Appendix, section
5.4.
The Model S104 Enhanced Smart Sensor op-
erates on a nominal power of +24 VDC. Pri-
mary DC power must be provided by the
customer unless one of the following General
Monitors Modules is being used with the
Model S104:
lDC110 Readout/Relay Display Module
with Power Supply & Relay Module
lDC130 Readout/Relay Display Module
lTA102A Trip Amplifier Module with a
PS002
The following General Monitors Modules
provide power connections for the Model
S104, but need a customer supplied DC
source:
lDC110 Readout/Relay Display Module
without Power Supply & Relay Module
lDC120 Dual Channel Display Module
lTA102A Trip Amplifier Module without
a PS002
Since the Model S104 is designed to operate
continuously, a power switch is not included
in order to prevent accidental system shut-
down.
NOTE: Power must remain disconnected
until all other wiring connections have been
made.
The maximum distance between the Model
S104 and the power supply is 4500 feet (1372
meters). See the Appendix (section 5.1.2) for
cable length specifications. The cable run
should be as short as possible.
figure 11
To connect +24VDC to the Model S104, con-
nect the red wire to TB1, position 7 (CE Mark
units - TB3, position 3), labeled +24VDC.
Connect the black wire to TB1, position 6
(CE Mark units - TB3, position 2), labeled
COM (figure 11).
3.5 Applying Power
Before applying power to the system for the
first time, all wiring connections should be
checked for correctness and the housing cover
replaced. Upon first power-up the sensor may
take up to fifteen minutes to stabilize.
At the initial application of power, or after a
fault condition, the unit will enter a fifty sec-
ond Start-Up mode. During this period the
display will indicate an SU.
GENERAL MONITORS
Model S104
9

Installation
3.6 Maintaining the X/P Integrity
The Model S104 is rated explosion proof for
Class I, Division 1, Group B, C & D hazard-
ous locations. Some of the factors that influ-
ence the explosion proof integrity of the
Model S104 Housing:
lStrength of the enclosure material
lThickness of the enclosure walls
lFlame path between the housing and
cover
lFlame path of threaded joints
The acceptable limits for explosion proof
housings that are used in Class I hazardous lo-
cations are defined in CSA Standard C22.2
No.30-M1986.
Anytime the cover of the smart sensor hous-
ing is removed or the cover bolts are loos-
ened, the flame path between the lid and the
housing is effected. If power is left on before
loosening the cover bolts on the Model S104,
it will be necessary to de-classify the area.
When replacing the cover, the gap between
the lid and the housing should be less than
.0015 inch (.038 mm). This can be verified
by tightening the cover bolts to a torque set-
ting of 50 inch-pounds or by using a feeler
gauge to ensure the gap between the cover
and the housing is less than .0015 inch (.038
mm).
There are four entry holes in the Model S104
housing. These holes are dedicated for the
sensor, the calibration switch and conduit.
Each hole is tapped for 3/4 NPT threads. If a
particular entry hole is not used it must be
plugged during operation in the field. The
factory installs plugs for two of the entry
holes.
A plastic red cap plug is placed into the re-
maining hole and must be removed before
conduit can be attached to the housing.
An S104 without a display will have the fol-
lowing items placed in the remaining three
entry holes:
lA sensor, if present (if not, a plastic
red cap-plug)
lA calibration switch
lAn aluminum housing plug
An S104 with a display will have the follow-
ing items placed in the remaining three entry
holes:
lA sensor, if present (if not, a plastic
red cap-plug)
lTwo aluminum housing plugs
The sensor, calibration switch and aluminum
housing plugs have seven threads. Each of
these components is screwed into the housing
using five to seven turns. If it becomes neces-
sary to replace one of these components, the
user must use five to seven turns to ensure the
explosion proof integrity of the housing.
10 GENERAL MONITORS
Model S104

4.0 Operation
4.1 Calibration
Activating the Calibration Switch will auto-
matically disable the alarm circuits by sending
a 1.5mA (0mA optional) output signal. This
will prevent activation of the relay contacts
when using a General Monitors Readout/Re-
lay Display Module with the Model S104.
General Monitors recommends that the Model
S104 Combustible Gas Enhanced Smart Sen-
sor be calibrated one hour after start-up, and
that calibration be checked at least every
ninety (90) days to ensure system integrity.
General Monitors is not implying that the cus-
tomer should expect problems with sensor life
or stability but “frequent” calibration checks
merely ensure the integrity of the life protect-
ing equipment.
The above statement is not intended to dis-
courage the customer from checking calibra-
tion more frequently. Frequent calibration
checks are recommended for environments
that have problems such as mud collecting on
the sensor head, sensors accidentally being
painted over, etc.
NOTE:A calibration check consists of ap-
plying a known concentration of gas to the
sensor and observing the reading on the
Model S104, the Readout/Relay Module, or
other computer data collecting systems.
General Monitors recommends that a calibra-
tion schedule be established and followed. A
log book should also be kept showing calibra-
tion dates and dates of sensor replacement.
Procedure with digital display:
lIf it is suspected that combustible gas is
present, it will be necessary to purge the
sensor environment with Zero Air. If
Zero Air is not available, cover the sensor
for about thirty seconds before applying
the calibration gas. Zero Air is air that is
hydrocarbon free.
figure 12
lPlace the magnet over the GMI Logo on
the cover (figure 12) of the unit and hold it
there until “AC” (figure 13) appears on
the display (about ten seconds). Allow
about five seconds for the unit to acquire
the zero reading before applying the
calibration gas. If the GMI Portable Purge
Calibrator (P/N 1400150) is not used
when calibrating the Model S104 with
Methane (CH4), the SPAN gas flow rate
needs to be 440cc/min to 460cc/min. See
Appendix, section 5.4.
11
figure 13
GENERAL MONITORS
Model S104

Operation
Calibration (continued)
lApply a 50% LEL gas concentration to the
sensor. The display will change from
“AC” to “CP” (figure 14) indicating that
the sensor is responding to the calibration
gas.
lAfter one or two minutes the display will
change from “CP” to “CC” (figure 15)
indicating that the calibration is complete.
lRemove the gas and wait for the unit to
return to normal operation. The display
will indicate less than 5% LEL and then
drop to “0” (figure 16).
lThe unit is now calibrated and the new
ZERO and SPAN values have been stored
in the non-volatile memory.
The Model S104 can be returned to normal
operation if the magnet is re-applied ninety
seconds after initiating the calibration se-
quence. If the Model S104 is placed in the
Calibration Mode and no gas is applied for six
minutes, the unit will revert to a Fault condi-
tion. Re-applying the magnet over the GMI
Logo will return the unit to the Calibration
Mode.
Procedure without digital display:
See figure 17 for LED flashing sequences.
lIf it is suspected that hydrocarbons are
present, it will be necessary to purge the
sensor environment with Zero Air. If
Zero Air is not available, cover the sensor
for about thirty seconds before applying
the calibration gas. Zero Air is air that is
hydrocarbon free.
lPlace the magnet next to the end of the
LED switch and hold it there until the
LED comes on steady.
lApply the calibration gas (50% LEL) and
wait for the LED to blink slowly (about
one or two minutes).
lRemove the calibration gas and allow the
unit to see clean air.
lThe unit is now calibrated.
figure 14
figure 15
figure 16
figure 17
12 GENERAL MONITORS
Model S104

Operation
Calibration (continued)
Test Gas Mode (available with display only):
If it is desired to check the sensor for its re-
sponse without sending a gas concentration
signal to a remote display device, this can be
accomplished by placing the Model S104 into
the “Test Gas Mode”. Procedure for checking
the calibration:
lPlace the magnet over the GMI Logo on
the cover of the Model S104. Remove the
magnet when a flashing pair of bars, “-
-”, (see figure 18) appears on the display
(about three seconds).
figure 18
lApply the test gas to the sensor and the
value of the gas concentration will be
indicated by the flashing display in about
one to two minutes.
lWhen the reading has stabilized and the
test is complete, remove the gas and the
unit will return to normal operation when
the concentration drops below 5% LEL.
The “test” gas concentration must be at least
10% LEL before the unit will complete the
test sequence. If the Model S104 is placed in
the Test Gas Mode and no gas is applied for
six minutes, the unit will revert to a Fault con-
dition. Re-applying the magnet over the GMI
Logo will return the unit to normal operation.
Calibration Equipment:
The Portable Purge Calibrator is a compact,
accurate and safe system containing no explo-
sive gas. The lecture bottle is filled with a
standard 50% LEL mixture of gas/air. Using a
known gas/air mixture reduces the likelihood
of error in field calibration. The hose and cup
adapter permits calibration without having to
remove the sensor. The following pre-mixed
calibration gases at approximately 50% LEL
are available, in a lecture bottle, at 1200 psia,
8.3 MPa maximum pressure.
lButadiene
lButane
lEthane
lHydrogen
lMethane
lPropane
Methane and Hydrogen lecture bottles may be
returned to General Monitors for refilling. It
will be necessary to specify the gas. Spare
bottles containing these gases may be ordered.
The Portable Calibration Chamber is a 3 li-
ter (3000 cc) sample chamber with a spring
driven mixing fan. A porthole allows the
chamber to be placed on the sensor for calibra-
tion. A syringe is included for accurate meas-
urement of volatile test liquids. Sensors
should be calibrated to a specific vapor for
greatest accuracy. A hydrocarbon sensor cali-
brated for 50% LEL Acetone, for example,
will detect all hydrocarbons and most combus-
tible solvent vapors. It will accurately read
ONLY the % LEL of Acetone. The indicated
measures of volatile liquids in the next column
produces 50% LEL vapor mixtures at 75°
Fahrenheit (25° Celsius) temperature and
standard pressure when used with the Portable
Calibration Chamber. See Appendix, section
5.4.
13
GENERAL MONITORS
Model S104

Operation
Volatile liquids are not supplied by General Monitors.
Below is a list of volatile liquids and the volume required
(in microliters) to produce 50% LEL in the 3 liter chamber.
Acetaldehyde 137
Acetic Acid 140
Acetone 113
Acetonitrile 96
Acrylonitrile 121
Amyl Acetate 100
Amylamine 156
Benzene 71
Butyl Acetate 137
Butyl Acylate 132
Butyl Alcohol 79
sec-Butyl Alcohol 95
tert-Butyl Alcohol 139
Butyl Cellosolve 88
Butyraldhyde 103
Cyclohexane 86
Decane 96
Diethyl Ketone 104
Diisobutyl Ketone 82
Dimethylformamide 104
p-Dioxane 105
Dodecane 84
Ether, Ethyl 120
Ethanol (Ethyl Alcohol) 119
Ethyl Acetate 120
Ethyl Amine 140
Ethyl Benzene 75
Ethylene Oxide 91
Gasoline 100 Octane 107
Heptane, Normal 94
Hexane, Normal 87
Isopentane 100
Isoprene 92
Isopropyl Alcohol 94
Isopropyl Ether 121
JP-4 Jet Fuel 183
Laktane 76
Methanol 149
Methyl Ethyl Ketone (MEK) 77
Methyl Metacrylate 112
Naptha (Petroleum Ether) 94
Octane 100
Pentane, Normal 106
Propanol 115
2-Propanol 93
Propyl Acetate 108
Propylamine 101
Propylbenzene 68
Propylene Oxide 99
Styrene 63
Tetradecane 80
Tetrahydrofuran 100
Tetrahydrofurfuryl Alcohol 89
Toluene 71
1,1,1-Trichlorethane 459
Trichloroethylene 440
Triethylamine 103
Vinyl Acetate 147
Vinyl Ethyl Ether 100
o-Xylene 67
p-Xylene 82
Xylenes 83
4.2 Digital Display Codes
The following codes will appear on the dis-
play when the unit is placed in a mode other
than the normal operating mode.
SU Start-Up
- - (steady) Magnetic Switch Activated
- - (flashing) Test Gas Mode
AC Automatic Calibration
CP Calibration in Progress
CC Calibration is Complete
F1 Failed to Zero during calibration
F2 Failed to complete the calibration
F3 Failed to Span during calibration
F4 Sensor Reference Bead Error
F5 Sensor Active Bead Error
F6 Low Supply Voltage
F7 EEPROM Verification Failure
F8 Negative Zero Drift
F9 Calibration check period exceeded
When the unit is in the normal operating
mode, the display will indicate the presence of
combustible gas in percent of the Lower Ex-
plosive Level (% LEL). The range of detec-
tion is from 0 to 99% LEL.
99 (flashing) Over-Range, a gas concentration
exceeding 100% LEL is present.
SU This is displayed for about fifty seconds
during start-up and after a Fault condition
has been corrected.
- - Appears on the display when the magnet
has been properly positioned over the
GMI Logo and when the Test Gas
Mode can be or has been entered.
14 GENERAL MONITORS
Model S104

Operation
Digital Display Codes (continued)
AC These codes appear on the display
CP during the calibration process. For
CC more information about these codes,
refer to Section 4.1 Calibration.
F1,F2,F3, These codes will appear on the
F4,F5,F6, display if a Fault condition occurs.
F7,F8,F9 For more information about these
codes, refer to Section 4.3 Fault
Codes & Their Remedies.
4.3 Fault Codes & Their Remedies
The Model S104 has self-diagnostics incorpo-
rated into the microprocessor’s program. If a
Fault is detected, the output signal will drop to
0mA and a Fault code will be displayed. The
output signal will inform a remote display
module that the Model S104 is in the Fault
Mode. The display will indicate a Fault code
that can be viewed at the sensor site. There
are nine Fault conditions that are monitored by
the microprocessor.
When a Calibration Fault (F1, F2, F3) has oc-
curred and has been corrected, the unit will
automatically revert to the calibration process
and the unit must be re-calibrated. If a Fault
other than a Calibration Fault occurs, after it is
corrected, the unit will return to the Start-Up
Mode (SU).
F1 = Failed to Zero during Calibration
Faulty Sensor - If both Catalytic Beads are
not closely matched. This may happen as a
sensor approaches the end of its useful life or
if the Beads have become corroded. AC-
TION - Replace the sensor.
Gas Present - If the magnet was applied with
a high level of gas present, the Model S104
will not be able to obtain a valid ZERO. AC-
TION - Ensure the sensor is in clean air.
F2 = Failed to complete the Calibration
This Fault will occur if the unit is placed in the
calibration mode and no gas has been applied
within six minutes.
F3 = Failed to Span during Calibration
Low Gas - If the gas concentration applied to
the unit does not give sufficient response for a
valid SPAN parameter. ACTION - Use the
correct gas concentration, i.e. 50% LEL.
Bad Sensor - If the sensor response has gone
below an acceptable level. ACTION - Re-
place the sensor.
NOTE:If the unit fails to calibrate and an F1
or an F3 code is displayed, the calibration
gas must be removed from the sensor and
the sensor must see clean air for at least five
minutes before a second calibration is initi-
ated.
15
GENERAL MONITORS
Model S104

Operation
Fault Codes & Their Remedies (continued)
F4 = Sensor Reference Bead Error
This fault may occur as a result of one of the
following:
lexcessive negative drift
lan open sensor reference bead
lthe sensor BLACK wire is disconnected
ACTION - Attempt to recalibrate the unit. If
this is unsuccessful make sure that the
BLACK sensor wire is connected to the termi-
nal block. If both of these actions do not cure
the fault condition, then replace sensor.
F5 = Sensor Active Bead Error
This fault occurs if the sensor active bead be-
comes open circuited or, if the sensor WHITE
or the sensor RED lead becomes disconnected.
ACTION - Check the WHITE and RED wires
or replace the sensor as appropriate.
F6 = Low Supply Voltage
This fault occurs if the supply voltage drops
below +17VDC approximately. ACTION -
Ensure that the supply voltage is at least
+20VDC at the Model S104.
Correcting this Fault will initiate the Start-Up
Mode.
NOTE:With long supply leads, a consider-
able voltage drop may occur due to the elec-
trical resistance of the leads.
The maximum cable resistance which the
Model S104 can tolerate is dependent on the
supply voltage. A maximum of 20 ohms per
conductor (40 ohms loop) at +24VDC mini-
mum, or a maximum of 10 ohms per conduc-
tor (20 ohms loop) at +20VDC minimum.
F7 = EEPROM Verification Failure
This fault occurs during calibration when an
attempt to verify the calibration parameters
just written to the non-volatile memory fails.
The usual cause of this is electrical interfer-
ence corrupting the data (although on rare oc-
casions it may indicate a problem within the
electronics module). ACTION - Place the
magnet over the GMI Logo and the unit will
attempt another EEPROM write and verify.
F8 = Negative Zero Drift
If the zero baseline of the sensor drifts 10% of
full scale below zero for more than 20 seconds
this fault will occur. ACTION - A routine re-
calibration will be required.
F9 = Calibration Check Period Exceeded
If the Model S104 is left in the Test Gas Mode
for more than six minutes without a Test Gas
being applied, this fault will occur. ACTION
- Place the magnet over the General Monitors
Logo to return the unit to normal operation.
NOTE: Anytime a sensor is replaced, the unit
should be disconnected from all alarms, as the
unit may go upscale upon power-up.
NOTE:Model S104 without display has
limited fault diagnostic capabilities. It can
sense calibration, sensor and low voltage
faults. See figure 17 for LED sequences.
16 GENERAL MONITORS
Model S104

5.0 Appendix
5.1 Specifications
5.1.1 System Specifications
Sensor Type:
Diffusion, low temp. catalytic bead
Standard industrial types: Combustible
Gas; Solvent Special; Standard and High
TemperatureVersions (See section 5.4)
Typical Life: 3 years in normal service
Warranty:
Two Years
Readout/Relay Modules (See section 5.4):
DC100 Single Channel Display
DC110 Eight Channel Display
DC120 X/P Dual Channel Display
DC130 Dual Channel Display
TA102A Single Channel, 02 Series
Fault Conditions Monitored:
Low DC Supply, Sensor Bead Open,
Calib. Out of Range, EEPROM Failure
Accuracy:
+3% LEL at ambient
Zero Drift:
Less than 5% per year
Response Time:
With 100% LEL Methane Applied,
T50 < 10 sec. & T90 < 30 sec.
Approvals:
FM approved
CSA certified to C22.2 No.152
Cenelec certified (display only with
SST flame arrestor sensors)
CE Mark approval against EMC Directive
and Product Safety
5.1.2 Electrical Specifications
Input Power:
24 VDC @ 250mA nom., 1A during SU
20 to 30 VDC range
Output Current: (0-22mA @ 300 Ohms max. load)
Fault: 0.0mA
Calibration: 1.5 mA (0.0mA optional)
0-100%LEL: 4 to 20mA
Over-range: 20 to 22mA
Electrical Classification:
Class I, Division 1, Groups B, C & D
NEMA 4x rated
Recommend Three Wire Shielded Cable:
Maximum distance between the Model
S104 and the power source.
AWG Feet Meters
22 750 228
20 1100 335
18 1600 488
16 2250 685
14 4500 1372
For interfacing with 250 ohm input
impedance devices, the following
maximum cable lengths apply, with
respect to the Analog Signal, with the
total loop resistance less than 300 ohms.
AWG Feet Meters
22 1600 488
20 2400 730
18 3800 1160
16 5200 1585
14 9000 2740
NOTE: Good design practices dictate cable
lengths conservatively shorter than the maxi-
mum given values.
17
GENERAL MONITORS
Model S104