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

[phone]

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
					Figure 7-6
	concentration reading on the controller will be				Cover Plate - Combustible Gas Module
	inaccurate and alarm level concentrations may be
	displayed. If false activation of the alarm relays
	will cause a problem disconnect the relay wiring				Comparing to the "GND" (ground) test point measure
	prior to adjustment or turn the module off using the
					"BRIDGE VOL" (bridge voltage) and adjust to 2.00 VDC
	CHANGE MODULE mode.
					using "BRIDGE ADJ" potentiometer. Turn counter-
		NOTE			clockwise to increase.
		Although all the necessary data can be collected with a
		voltmeter at the sensor module, some helpful information			7.5.3.2 ZERO ADJUSTMENT
		can be displayed or printed. See diagnostic codes 0004
		and 0008 in Appendix C.			Comparing to ground measure SIGNAL OUT and adjust to
	7.5.3 ADJUSTMENT PROCEDURE				0.18 VDC by turning ZERO ADJ potentiometer. Turn
					counter clock-wise to increase.
	Prior to reading voltages and making adjustments perform
	a visual inspection to confirm that there are no physical				7.5.3.3 SPAN ADJUSTMENT
	problems such as water in the electronics enclosure,
					1. Determine the concentration of the calibration
	wiring damage or corrosion.
	Use Figure 7-6 to locate test points during the following				gas (CG) in % LEL.
					2. Use the following formula to determine the
	procedures:
	Caution: The area must be free of flammable vapors or				response to the calibration gas at SIGNAL OUT.
					Voltage (Signal Out) = (CG+12)/60
	gases during any adjustments or maintenance procedures.
					For Example:

7.5.3.1 BRIDGE VOLTAGE ADJUSTMENT

Confirm that no combustible gas is present and remove sensor module cover.

If CG = 50% L.E.L Signal Out = (50+12)/60

= 1.03 volts

SERVICE

Page: 69

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.

•A LOW SENSITIVITY message during 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.

The LOW SENSITIVITY calculation is made to insure that 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.

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.

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 the following actions 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.

SERVICE

Page: 70

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:

	GAS			METHANE			PROPANE
				FACTOR			FACTOR
	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

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.)

SERVICE

Page: 71

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				Figure 7-7
displayed. If false activation of the alarm relays				Cover Plate - Oxygen Module
will cause a problem disconnect the relay wiring
prior to adjustment or turn the module off using

the "Change Module" mode.

				7.6.4 SENSOR REPLACEMENT
		NOTE		The oxygen sensor should be replaced when it can no
		Although all the necessary data can be collected with a
		voltmeter at the sensor module, some helpful information		longer be calibrated correctly or when the signal output
		can be displayed on the controller or printed. See		drops to zero. Generally this is every twelve to eighteen
		diagnostic codes 0004 and 0008 in Appendix C.		months. The Sentry clock keeps track of the age of the
	7.6.3 ADJUSTMENT PROCEDURE			sensor if it is correctly initialized in the "change module"
				mode.
	Prior to reading voltages and making adjustments perform
				When a new sensor is installed use the CHANGE MODULE
	a visual inspection to confirm that there are no physical
				menu selection to	answer yes	to	the "new	sensor?"
	problems such as water in the electronics enclosure,
				question. After	nine months	the	CHANGE	SENSOR
	wiring damage or corrosion.
				message will be displayed to warn that a new sensor
	Use Figure 7-7 to locate test points during the following
				should be installed.
	procedures.			The SENSOR FAILURE message for Oxygen sensors does
	7.6.3.1 SIGNAL ADJUSTMENT			not indicate a specific failure of the sensor but indicates
				that the sensor is not correctly connected to the
	It is unlikely that any electrical adjustment will be			electronics. If this message appears check that the sensor
	required except when a new sensor is installed.			harness is correctly installed to the connector on the
	To make the electrical adjustment connect a voltmeter to			bottom electronics board.
				When sensor replacement is required, open the cover of
	SIGNAL OUT (pos) and GND (ground) and use
	SENSITIVITY ADJ potentiometer to set the voltage equal to			the sensor module, remove the transmitter and disconnect
	1/10 of the actual oxygen concentration. In clean air the			the sensor wiring harness from the back of the transmitter.
	concentration is 20.9% so the voltage should be set at
	2.09 VDC.
			SERVICE
			Page:	72