Sierra Monitor Corporation 5000 User Manual
MODEL 5000
S E N T R Y
GAS MONITORING SYSTEM
Version 6
Sensors Service
APPLICABILITY & EFFECTIVITY
Effective for all Sentry systems manufactured after September 1, 1995.
Instruction Manual Part Number T12001-A1
Sierra Monitor Corporation
1991 Tarob Court, Milpitas, CA 95035
(408) 262-6611
Applicability & Effectivity
SMC sierra monitor corporation Sentry Instruction Manual - Version 6
7.5 COMBUSTIBLE GAS SENSOR MODULE
(5100-02)
7.5.1 DESCRIPTION
The Combustible Gas Module includes the sensor
and electronic assembly installed in an explosion
proof housing. The sensor screws into one hub of
the enclosure and plugs into the bottom
electronics card via a six pin connector. Cabling
to the controller connects to a three pin spring
loaded terminal strip.
7.5.2 TROUBLE ANALYSIS
Electrical adjustment, or replacement of the
sensor will be necessary under the following
conditions:
• Controller displays the following error
messages:
CHK BRIDGE VOLT
SENSOR FAILURE
LOW SENSITIVITY
• False readings or alarms are received
due to sensor inaccuracy.
Warning: : During sensor adjustments the
concentration reading on the controller will be
inaccurate and alarm level concentrations may be
displayed. If false activation of the alarm relays
will cause a problem disconnect the relay wiring
prior to adjustment or turn the module off using the
CHANGE MODULE mode.
NOTE
Although all the necessary data can be collected with a
voltmeter at the sensor module, some helpful information
can be displayed or printed. See diagnostic codes 0004
and 0008 in Appendix C.
7.5.3 ADJUSTMENT PROCEDURE
Prior to reading voltages and making adjustments perform
a visual inspection to confirm that there are no physical
problems such as water in the electronics enclosure,
wiring damage or corrosion.
Use Figure 7-6 to locate test points during the following
procedures:
Caution: The area must be free of flammable vapors or
gases during any adjustments or maintenance procedures.
7.5.3.1 BRIDGE VOLTAGE ADJUSTMENT
Confirm that no combustible gas is present and remove
sensor module cover.
Figure 7-6
Cover Plate - Combustible Gas Module
Comparing to the "GND" (ground) test point measure
"BRIDGE VOL" (bridge voltage) and adjust to 2.00 VDC
using "BRIDGE ADJ" potentiometer. Turn counterclockwise to increase.
7.5.3.2 ZERO ADJUSTMENT
Comparing to ground measure SIGNAL OUT and adjust to
0.18 VDC by turning
ZERO ADJ potentiometer. Turn
counter clock-wise to increase.
7.5.3.3 SPAN ADJUSTMENT
1. Determine the concentration of the calibration
gas (CG) in % LEL.
2. Use the following formula to determine the
response to the calibration gas at
SIGNAL OUT.
Voltage (Signal Out) = (CG+12)/60
For Example:
If CG = 50% L.E.L
Signal Out = (50+12)/60
= 1.03 volts
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SMC sierra monitor corporation Sentry Instruction Manual - Version 6
3. Using a Sierra Monitor Model 1200-26 Gas
Calibrator with a Sierra Monitor Model 535800 calibration adapter, or Model 5360 Gas
Delivery Fitting. Apply the calibration gas at a
flow rate of 100 cc/min. until the signal out
voltage stops changing (approx. 2 minutes).
Then adjust span adj. potentiometer to the
calculated value.
4. Remove the calibration gas and wait for the
voltage to drop. If the voltage is below 0.30
VDC the procedure is complete. If the voltage
is above 0.30 VDC repeat the zero and span
adjustments.
5. Calibrate the sensor using the instruction
manual procedure.
LOW SENSITIVITY message during
• A
calibration indicates one of the two
conditions for a combustible sensor:
• The zero gas voltage must be less than
.3 volts.
• The new span change (span voltage less
zero voltage) must exceed 30% of the
calculated span change.
For Example:
Zero gas voltage = .20 VDC
Span voltage = .43 VDC
Span change is .43-.2 = .23 VDC
As the calculated span value (from
step 5 above) is 1.03, the calculated
span change is: 1.03-.2 = .87
By calculation: 30% of .87 = .26
The new span change (.23) is less than
30% of the calculated span change so a
LOW SENSITIVITY message will be
displayed.
LOW SENSITIVITY calculation is made to insure that
The
the calibration does not adjust the electronics so that the
"gain" is large enough to cause false alarms due to minor
drift or due to minimal electronic noise.
PIN FUNCTION WIRE COLOR
1 DETECTOR WHITE
2 COMPENSATOR BROWN
3 CALIB. SW. RED
4 DETECTOR BLACK
5 DRAIN BARE
6 CALIB. SW. GREEN
Table 7-5
Combustible Gas Sensor
Wiring Pin Out
1. Detector element resistance should be between 1.5 to
2 ohms.
2. Compensator element resistance should be between
1.5 to 2 ohms.
3. Calibration switch should be open in normal
operation and should close when the calibration
magnet is applied.
If the sensor fails any of these tests it should be replaced.
If the sensor passes these tests the electronics are suspect
and BOTH the sensor and electronics should be replaced.
(The electronics and sensor which are removed should be
returned to the factory for evaluation).
When a new sensor is installed th e follo wing action s must
be taken:
• Make the bridge voltage adjustment
immediately to avoid over-voltage damage to
the sensor.
• Use diagnostic code 0020 to establish nominal
value calibration.
• Allow 24 hours for full stabilization of the
sensor, recheck the zero and span adjustments
and calibrate the sensor module.
7.5.4 SENSOR REPLACEMENT
If any of the above adjustments cannot be completed
successfully the sensor and/or electronics will require
replacement. To check the sensor unplug it from the
electronics and remove from the housing so that
continuity and resistance tests can be made. Table 7-4
provides the pin out for the sensor assembly.
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SMC sierra monitor corporation Sentry Instruction Manual - Version 6
7.5.5 COMBUSTIBLE GAS SCALING FACTORS
For combustible gas monitoring, a calibration standard of Methane or Propane my be used in conjunction with scaling
factors to cause Sentry concentration display and alarm function in %LEL scale of another gas as follows:
GAS METHANE PROPANE
FACTOR FACTOR
Acetaldehyde 60 109
Acetic Acid 54 98
Acetic Anhydride 46 83
Acetone 52 94
Acetylene 57 103
Alkyl Alcohol 51 92
Ammonia 126 229
n-Amyl Alcohol 33 59
Aniline 39 71
Benzene 41 74
Biphenyl 25 45
1,3-Butadiene 56 101
n-Butane 58 106
iso-Butane 52 94
Butene-1 45 82
cis-Butene-2 48 88
trans-Butene-2 51 92
n-Butyl Alcohol 34 62
iso-Butyl Alcohol 53 96
tert-Butyl-Alcohol 74 134
n-Butyl Benzene 31 57
iso-Butyl Benzene 32 58
n-Butyric Acid 38 69
Carbon Disulfide 18 32
Carbon Monoxide 75 137
Carbon Oxysulphide 93 169
Chlorobenzene 34 62
Cyanogen 89 162
Cyclohexane 41 74
Cyclopropane 62 113
n-Decane 33 59
Diethylamine 49 88
Dimethylamine 58 105
2,3-Dimethylpentane 40 72
2,3-Dimethylpropane 40 72
Dimethylsulphide 43 79
1,4-Dioxane 45 81
Epichlorohydrin 45 82
Ethane 68 123
Ethyl Acetate 51 93
Ethyl Alcohol 73 132
Ethylamine 53 95
Ethyl Benzene 36 65
Ethyl Bromide 91 165
Ethyl Chloride 57 103
Ethylcyclopentane 40 72
Ethylene 71 128
Ethylenedichloride 66 120
Ethyleneoxide 52 94
NOTES:
Diethyl Ether 46 84
Dimethoxyethane 42 75
Dimethyl Ether 63 113
Dimethylformamide 46 83
Ethyl Formate 44 80
Ethylmercaptan 56 102
n-Heptane 39 70
n-Hexane 37 67
Hydrazine 45 82
Hydrogencyanide 48 86
Hydrogen 77 139
Hydrogen Sulfide 41 74
Methane 100 181
Methyl Actetate 50 90
Methyl Alcohol 86 156
Methylamine 77 140
Methyl Bromide 90 162
Methyl Chloride 102 186
Methylcyclohexane 44 80
Methylenedichloride 93 168
Methylethylether 44 80
Methylethylketone 41 75
Methyl Formate 67 121
Methylmercaptan 61 110
Methylpropionate 51 93
Methyl n-propylketone 40 73
Napthalene 34 62
Nitromethane 34 62
n-Nonane 31 57
n-Octane 37 68
n-Pentane 46 83
i-Pentane 46 84
Propane 55 100
n-Propyl Alcohol 47 85
n-Propylamine 48 88
n-Propylchloride 50 90
Propylene 52 93
Propyleneoxide 46 83
iso-Propylether 44 79
Propyne 42 75
Toluene 40 73
Triethylamine 40 72
Trimethylamine 48 88
Vinylethylether 42 76
o-Xylene 36 65
m-Xylene 39 71
p-Xylene 39 71
JP-4 (Jet Fuel) 41 73
GAS METHANE PROPANE
FACTOR FACTOR
1. Scaling factors are not FMRC approved.
2. Base data source: EEV sensor specification catalog. (EEV claims some data is the result of specific tests, other
data is empirically derived.)
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SMC sierra monitor corporation Sentry Instruction Manual - Version 6
7.6 OXYGEN MODULE (5100-03)
7.6.1 DESCRIPTION
The Oxygen Module includes the electronic
assembly installed in an explosion proof housing
and the electrochemical sensor connected to one
hub of the enclosure. Cabling from the controller
connects to a three pin spring loaded terminal
strip.
7.6.2 TROUBLE ANALYSIS
Electrical adjustment, or replacement of the
sensor will be necessary under the following
conditions:
• Controller displays the following error
messages:
CHANGE SENSOR
SENSOR FAILURE
REPLACE SENSOR
• False readings or alarms are received due to
sensor inaccuracy.
Warning: During sensor adjustments the
concentration reading on the controller will be
inaccurate and alarm level concentrations may be
displayed. If false activation of the alarm relays
will cause a problem disconnect the relay wiring
prior to adjustment or turn the module off using
the "Change Module" mode.
NOTE
Although all the necessary data can be collected with a
voltmeter at the sensor module, some helpful information
can be displayed on the controller or printed. See
diagnostic codes 0004 and 0008 in Appendix C.
7.6.3 ADJUSTMENT PROCEDURE
Prior to reading voltages and making adjustments perform
a visual inspection to confirm that there are no physical
problems such as water in the electronics enclosure,
wiring damage or corrosion.
Use Figure 7-7 to locate test points during the following
procedures.
7.6.3.1 SIGNAL ADJUSTMENT
It is unlikely that any electrical adjustment will be
required except when a new sensor is installed.
To make the electrical adjustment connect a voltmeter to
SIGNAL OUT (pos) and GND (ground) and use
SENSITIVITY ADJ potentiometer to set the voltage equal to
1/10 of the actual oxygen concentration. In clean air the
concentration is 20.9% so the voltage should be set at
2.09 VDC.
Figure 7-7
Cover Plate - Oxygen Module
7.6.4 SENSOR REPLACEMENT
The oxygen sensor should be replaced when it can no
longer be calibrated correctly or when the signal output
drops to zero. Generally this is every twelve to eighteen
months. The Sentry clock keeps track of the age of the
sensor if it is correctly initialized in the "change module"
mode.
When a new sensor is installed use the
CHANGE MODULE
menu selection to answer yes to the "new sensor?"
question. After nine months the
CHANGE SENSOR
message will be displayed to warn that a new sensor
should be installed.
SENSOR FAILURE message for Oxygen sensors does
The
not indicate a specific failure of the sensor but indicates
that the sensor is not correctly connected to the
electronics. If this message appears check that the sensor
harness is correctly installed to the connector on the
bottom electronics board.
When sensor replacement is required, open the cover of
the sensor module, remove the transmitter and disconnect
the sensor wiring harness from the back of the transmitter.
SERVICE
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