Instructions 95-8400-01
PathWatch™ Open Path IR Beam Detector
PW9200A1 Series
Detector Electronics Corporation
6901 West 110th Street •Minneapolis, Minnesota 55438 USA
Tel: 952.941.5665 or 800.765.3473 •Fax: 952.829.8750
9/00 95-8400-01
Section I- General Information
General Description ..........................................1
Features ............................................................1
Specifications ....................................................2
Functional Description ......................................2
Transmitter ...................................................2
Receiver ......................................................2
Section II - Operation
Safety Information .............................................4
Explosion-Proof Integrity .............................4
Personnel Safety .........................................4
Front Panel Controls ..........................................4
Installation .........................................................6
Inspection ....................................................6
Site Requirements .......................................7
Mounting .....................................................7
Initial Setup ........................................................9
Optical Alignment/Signal Strength ..................10
Operation/Performance Check .......................11
Alignment ..................................................12
Signal Strength ..........................................12
Output Zero ...............................................12
Heavy Hydrocarbon Response Confidence
Test ............................................................12
Status Alarm Confidence Test ...................12
Instrument Output ...........................................12
Calibration .......................................................13
Calibration Equipment ...............................13
Procedure ..................................................13
Use of the Calibration Graph ....................14
Hydrocarbon Vapor Alarm Threshold
Adjustment ................................................15
Section III - Maintenance
General Precautions ........................................16
General Information .........................................16
Access to Internal Components ......................16
P.C. Board and Assembly Replacement .........17
Scheduled Maintenance .................................18
Cleaning of Optical Components ..............18
Replacement of Filterwheel Motor .............19
Replacement of Transmitter Lamp ............19
Troubleshooting ...............................................20
Device Repair and Return ...............................22
Ordering Information .......................................22
Recommended Spare Parts ......................22
Appendix
List of Illustrations
Figure 1 - Functional Block Diagram .................3
Figure 2 - Front Panel Controls ..........................5
Figure 3 - Location of Receiver Boards and
Assemblies ....................................7
Figure 4 - Pan-Tilt Mount ...................................8
Figure 5 - Detector Mounting ............................8
Figure 6 - System Interwiring Diagram ..............9
Figure 7 - Calibration Equipment ....................13
Figure 8 - Calibrator Hookup ...........................14
Table of Contents
i
Section 1
General Information
The installation, operation and maintenance instructions contained in this manual are for use by qualified
personnel only. All personnel assigned to this equipment should read the instructions provided before initiating any procedures. The manual should be maintained on file so that it is available to installation, operation and maintenance personnel. To avoid injury to
personnel or damage to the equipment, do not perform any procedures other than those described in
this manual unless instructed by the factory or qualified by training.
The information contained in this manual is proprietary to Detector Electronics Corporation and is
intended for the sole purpose of installing, operating
and maintaining the PathWatch™ Open Path IR Beam
Detector.
GENERAL DESCRIPTION
The PathWatch™ open path leak detector is an electro-optical instrument that monitors hydrocarbon
vapors along an open surveillance path. The instrument is designed to operate remotely and to enable
vapor detection in difficult locations. Vapor detection
is based on changes in infrared absorption in the
spectral region of 3 to 4 microns.
The system consists of a transmitter and a receiver,
which can be separated by a distance of 100 meters
or more and are optically aligned. The transmitter
projects an infrared beam through the area under
surveillance to the receiver. In the receiver, the
infrared beam alternately passes through two narrow
band interference filters, a hydrocarbon wavelength
and a reference wavelength. A ratio of the reference
signal to the hydrocarbon signal is computed to provide an output signal proportional to the total hydrocarbon content in the beam path. Because it is an
open path system, the instrument’s measurement is a
function of gas concentration (expressed in ppm)
times the length of the surveillance path (expressed in
meters). Thus, the instrument’s output indicates the
average vapor concentration over the entire path
length.
A hydrocarbon alarm relay is activated when the ratio
signal exceeds the adjustable threshold, which corresponds to a selected average vapor concentration in
the path. A separate instrument status alarm relay is
activated when the infrared signal transmission is weak
or blocked, or when an instrument malfunction occurs.
FEATURES
• Active system provides more sensitivity than other
beam detectors.
• Incorporates premium, fundamental-band IR
absorption filters.
• No inherent source of drift.
• Monitors areas from 20 meters to 100 meters long.
• Single pass, straight line approach ensures maxi-
mum beam integrity.
• Single sensor for both active and reference channels.
• Internal fault alarm.
• Dual sensitivity and dual vapor options for different
environments.
• Easy alignment with wide margin for error.
• Capable of “around-the-corner” monitoring.
• Rugged, easy to use pan-tilt mounting bracket.
• Calibrated with real gas.
• Eye safe beam.
• Rugged, explosion-proof construction.
• Cooled IR sensor and air purge port offers potential
for operation in high temperature environments.
• Modular design for easy service.
• Optical surfaces easily protected from the elements.
• CSA certified.
INSTRUCTIONS
PathWatch™ Open Path
IR Beam Detector
PW9200A1 Series
©Detector Electronics Corporation 2000 9/00 95-8400-01
DET -TR O NICS
®
SPECIFICATIONS
HOUSING SIZE—
Transmitter and receiver dimensions are identical:
12-1/4 inches (W) x 11-1/2 inches (H) x 9-1/2 inches
(D).
WEIGHT—
Transmitter: 38 lb (17.2 kg).
Receiver: 42 lb (19 kg).
MOUNTING—
3/8-16 bolts (4 per housing) to a pan-tilt mount. The
mount interfaces between the instrument housings
and the user supplied vertical mounting pipes (4.5
inch O.D.).
OPERATING VOLTAGE—
Standard: 105 to 125 VAC, 50/60 Hz.
The incoming power line is fused internally to protect
the instrument from damage. These fuses are accessible on the front panel. On the 4 to 20 ma Output
Board, the 4 to 20 ma module is also fused.
POWER CONSUMPTION—
Transmitter: 30 watts.
Receiver: 60 watts.
OPERATING TEMPERATURE—
In ambient air with instrument shaded from direct sunlight: –4°F to +110°F (–20°C to +43°C) at 60 Hz,
–4°F to +100°F (–20°C to +38°C) at 50 Hz.
OPERATING DISTANCE (transmitter to receiver)—
Maximum: 328 feet (100 meters).
Minimum: 66 feet (20 meters).
VOLUME MONITORED—
A cylinder with a diameter of approximately 8 cm and
a length determined by the separation distance of the
transmitter and receiver.
SENSITIVITY (using heavy HC filters)—
100 ppm-meters minimum for heavy hydrocarbons.
WARNING
If the instrument is furnished with heavy hydrocarbon filters, it will not respond to ethylene or
methane. Contact the factory for information on
sensitivity to these vapors.
RESPONSE TIME—
63% of final reading within 10 to 20 seconds after a
step change in hydrocarbon vapor concentration.
HYDROCARBON VAPOR ALARM OUTPUT—
SPST relay, rated at 7 amperes continuous, 120
vac/240 vac or 28 vdc. Also rated at 1/3 HP at 120
vac, 1/2 HP at 240 vac. Contacts are closed under
normal clean air conditions and open when vapors
are detected.
OBSTRUCTION/FAULT STATUS OUTPUT—
SPST relay, rated at 7 amperes continuous, 120
vac/240 vac or 28 vdc. Also rated at 1/3 HP AT 120
vac, 1/2 HP AT 240 vac. Contacts are closed under
normal conditions and open when the beam is interrupted or a malfunction occurs.
ANALOG OUTPUT—
A 0 to 10 vdc analog output is available from the
instrument with 0 vdc corresponding to clean air. The
analog output increases as the hydrocarbon vapor
increases with +10 vdc corresponding to full scale
hydrocarbon vapor concentration along the monitored
path. The concentration corresponding to full scale is
adjustable over a ±50% range.
HAZARDOUS ENVIRONMENT CERTIFICATION—
Canadian Standards Association certified for operation in Class I, Division 1, Groups C and D environments and CSA enclosures Type 3 and 4.
FUNCTIONAL DESCRIPTION
A functional description of the operation of the
PW9200 is detailed in the following paragraphs and is
illustrated in Figure 1.
TRANSMITTER
The transmitter projects a beam of light toward the
receiver along the path to be monitored. A tungsten
halogen lamp is mounted at the focal point of a
parabolic reflector in the transmitter housing.
RECEIVER
The receiver contains the optical, mechanical, and
electrical components for receiving the light emitted
by the transmitter and processing the signal to an output that is proportional to the average hydrocarbon
content present in the volume monitored.
Receiver Lens
Light enters the receiver through the infrared transmitting lens. The lens focuses the incoming light onto
the face of the infrared photodetector.
2
Filterwheel Motor
This motor is a small 115 vac shaded pole ball bearing motor. The filterwheel is attached to the motor
shaft.
Filterwheel
The filterwheel is located between the receiver lens
and the photodetector. It contains the DENOMINATOR (active) and NUMERATOR (reference) optical
interference filters. Rotating at a rapid rate, the filterwheel chops the incoming light beam and alternately
passes infrared light at the two distinct wavelengths
to the photodetector.
Sync Pickoff
The sync pickoff is a small U-shaped optical switch,
which is mounted on the rear panel printed circuit
board and straddles the filterwheel. It senses when
each filter is in front of the infrared photodetector and
generates the synchronization signal.
Photodetector
The infrared photodetector is mounted at the focal
point of the receiver lens. The photodetector converts
the intensity of the incoming infrared light to a proportional electrical signal. It alternately senses the light
intensity at both wavelengths during each revolution
of the filterwheel. The photodetector is thermo-electrically cooled to increase the sensitivity to infrared light.
Amplifiers
The signal at the photodetector is amplified by the
preamplifier circuitry. The gain of the preamplifier
can be adjusted with a potentiometer to optimize the
signal strength for long or short operating distances.
The amplified signal is fed to the AGC amplifier,
which maintains the signal within the proper operating
range.
Signal Processing Electronics
The signal from the AGC Amplifier is separated into
two outputs: active (DENOMINATOR) and reference
(NUMERATOR).
Ratiometer
The ratiometer circuit generates an analog output by
calculating the ratio of the NUMERATOR (reference)
signal to the DENOMINATOR (active) signal.
Optional 4 To 20 Milliampere Converter
This option converts the 0 to 10 vdc voltage (RATIO
output) into a 4 to 20 ma current. A load resistor is
connected between the RATIO output and the analog
ground and can be any value between 0 and 500
ohms.
3 95-8400
Figure 1—Functional Block Diagram
SIGNAL
PROCESSING
ELECTRONICS
RATIOMETER
OPTIONAL
4 TO 20 MA
CONVERTER
THRESHOLD
DETECTOR
THRESHOLD
DETECTOR
STATUS
ALARM
RELAY
ALARM
RELAY
OPTIONAL
ANALOG
OUTPUT
ANALOG
OUTPUT
AMPLIFIER
MOTOR
INFRARED
PHOTO
DETECTOR
THERMOELECTRIC
COOLER
CONTROL
TRANSMITTER
LAMP
VAPOR CLOUD
BEING DETECTED
RECEIVER OPTICS
SYNC PICKOFF
MANUAL
GAIN
CONTROL
DENOM.
NUM.
MODE
SELECT
RATIO
OPTICAL
FILTERS
FILTER
WHEEL
TRANSMITTER
OPTICS
REGULATED
DC
POWER
SUPPLY
ADJUST
A1393
Threshold Detector:
Hydrocarbon Vapor Alarm Relay
The threshold detector activates when the RATIO voltage increases above a preset value. Activation of the
threshold detector causes the vapor alarm relay to
energize. The threshold level at which the hydrocarbon vapor alarm relay is energized can be adjusted
and tested on the front panel.
Threshold Detector:
Obstruction/Instrument Status Alarm Relay
The threshold detector activates when the NUMERATOR (reference) voltage approaches zero. When the
threshold detector activates, the obstruction/instrument status alarm relay to de-energizes. Because the
relay is energized in normal operation and is de-energized when the beam is blocked or when an instrument malfunction occurs, the alarm is fail-safe.
Section 2
Operation
SAFETY INFORMATION
EXPLOSION-PROOF INTEGRITY
WARNING
The PW9200 housings or associated junction
boxes must never be opened when circuits are
alive and hazardous vapor conditions may exist.
Ensure that no hazardous vapor conditions exist
in procedures where the cover, window assembly or junction box is to be opened when circuits
are alive.
CAUTION
If power is to be disconnected for an extended
period, e.g. over one week, the instrument
should be removed to a protected environment.
Special precautions must be taken with the PW9200
to ensure the integrity of the explosion-proof housings. When the instrument is in operation, the window
assemblies must be securely tightened. The cover
bolts must be torqued to 20 foot pounds.
Scratches may affect the strength of the instrument
windows, so care must be taken to avoid scratching
them during installation, operation and servicing.
Similarly, the mating surfaces of the cover and the
housing flange should not be scratched and these
surfaces should be protected during servicing.
The light beam projected by the PW9200 transmitter
could cause combustible materials within its path to
ignite or raise the temperature of an object within its
path above the self-ignition temperature of some
gases. Check the temperature code for the transmitter wattage used (see instrument nameplate) and do
not install the instrument at any location where this
dangerous condition could occur.
PERSONNEL SAFETY
The American Conference of Governmental Industrial
Hygienists (ACGIH) has established threshold limit
values (TLVs) or maximum allowable exposures to
bright light sources during an eight hour workday.
According to ACGIH, “these values are to be used as
guides to the control of exposure to light and should
not be regarded as the fine line between safe and
dangerous levels”.
WARNING
It is possible to exceed the ACGIH limit values by
viewing the instrument’s light source directly from
the center of the light beam at distances less
than approximately ten feet from the source. DO
NOT stare directly into the light source at close
range.
As with the sun, which greatly exceeds the Threshold
Limit Values established by the ACGIH, the eye’s selfprotection mechanism (blinking) activates and automatically prevents overexposure. However, close
range viewing of the transmitter beam must be avoided.
FRONT PANEL CONTROLS
Front panel controls are described in the following
paragraphs and are illustrated in Figure 2. Access to
the front panel controls is gained by removing the
receiver window assembly.
OUTPUT ZERO POTENTIOMETER
The ZERO adjustment potentiometer is used to set the
analog output (RATIO) to zero volts when the instrument views hydrocarbon-free air.
MODE SWITCH
The MODE selector switch permits adjustment of the
instrument’s response time and testing of the alarm
circuits.
4
5 95-8400
Align
A shorter response time (approximately 2 seconds) is
used only during the alignment and testing process.
Operate
A longer response time (approximately 20 seconds) is
used during normal operation to compensate for short
term signal variations and to prevent the hydrocarbon
alarm from activating on short duration vapor clouds.
Test
Test mode activates the hydrocarbon alarm circuits.
CALIBRATION ADJUSTMENT POTENTIOMETER
The CALIBRATION ADJUSTMENT potentiometer is
used to scale the RATIO output voltage for the
desired span. During factory calibration, the RATIO
output voltage is set to correspond to the desired
ppm reading at full scale.
SENSITIVITY SWITCH
The SENSITIVITY selector permits adjustment of the
range or span of the instrument’s sensitivity. It is recommended that the selector be set for Hi. Mid and Lo
are used for specialized applications.
ZERO
OUTPUT
OPERATE
ALIGN
TEST
O
V
mA
LO
MID
HI
CALIBRATION
ADJUSTMENT
SET-
POINT
RATIO DENOM NUM
MODE
SENSITIVITY
VAPOR ALARM
OUTPUT
SIG GND OUT OPT
OUTPUT
SELECT
A1395
SPARE
FUSE
1 A
FUSE 1 A
ADJUST
Figure 2—Front Panel Controls
Hi
This position sets the instrument for the highest sensitivity available. PW9200 instruments are factory set
and calibrated at HI sensitivity.
Mid
This position decreases the sensitivity of the instrument by a factor of 3.
Lo
This position decreases the sensitivity of the instrument by a factor of 10.
HC ALARM
Adjust
The HC ALARM Adjustment potentiometer is used to
set the threshold at which the RATIO voltage energizes the hydrocarbon alarm relay. The HC ALARM is
adjustable from 10% full scale to 100% full scale.
Setpoint (grey)
The HC ALARM Set Point test jack is used to access
the HC alarm threshold setting.
OUTPUT
The OUTPUT test jacks permit access to the NUMERATOR, DENOMINATOR and RATIO outputs:
Ratio (brown)
RATIO output (ratio of the two IR beams): 0 to 10
volts.
Denom (red)
DENOMINATOR output (intensity of the HC beam): 0
to 600 mv.
Num (green)
NUMERATOR output (intensity of the reference
beam): 0 to 600 mv.
SIG GND (green)
The SIG GND test jack permits access to signal
ground.
OUT OPT (violet)
The OUT OPT test jack permits access to the optional
RATIO output (used only with the options P.C. board).
FUSE
The power line fuse has been located on the front
panel for accessibility.
OUTPUT SELECT SWITCH
This switch is used to select the type of RATIO output
that is available at the junction box:
O - Optional output mode
This position is available for optional processing data
output.
V - Voltage output mode
This position sets the RATIO output for 0 to 10 vdc.
MA - Milliamp output mode
This position sets the RATIO output for 4 to 20 ma, if
this option has been installed.
INSTALLATION
INSPECTION
Since the instrument could be subjected to shock or
vibration during shipping, an inspection of the connections and filterwheel is recommended.
Prior to the initial setup of the instrument, open the
housing (see “Access to Internal Components” procedure) and check that the printed circuit board(s) are
securely held in the connector(s). If a board has
become dislodged, return it to the proper connector.
The synchronous demodulator board is on the right of
the filterwheel and the options board is on the left
(See Figure 3). Observe the location of the keys and
do not attempt to insert the printed circuit board(s)
backwards. Be certain that the board is firmly seated
in the connector and that both the top and bottom are
held by the card guides. Check that the ribbon connectors on the AGC/TE cooler board and on the rear
panel board are fully engaged and that the latches
are locked. Rotate the filterwheel to check that it
spins freely. Check that the two receiver connectors
are securely engaged.
6
SITE REQUIREMENTS
If the instrument is located where it is exposed to
direct sunlight, a sunshield should be installed to
keep the instrument housing temperature within the
specified operating limit.
If the instrument is installed in a high temperature,
high humidity or corrosive atmosphere, instrument air
or dry nitrogen purge is recommended.
Do not install the instrument so that the receiver
directly faces an intense heat source.
CAUTION
If power is to be disconnected for an extended
period, (e.g., over one week) the instrument
should be removed to a protected environment.
MOUNTING
The PW9200 is installed so that the transmitter and
receiver face each other. If a mirror is used with the
PW9200, see APPENDIX for special mount assembly
and alignment procedures.
The transmitter and receiver are bolted to the pan-tilt
mount, illustrated in Figures 4 and 5. This mount per-
mits height, horizontal pan and vertical tilt adjustments to optically align the instrument for maximum
signal strength. The pan-tilt mount attaches to a user
supplied 4 inch I.D. (4.5 inch O.D.) vertical pipe,
which must be securely stabilized to assure retention
of alignment over time and temperature fluctuations.
The vertical pipe should also be isolated against
external vibration.
1. Loosen the bolt holding the alignment target to
the back of the front plate and rotate the target
180°. Add the two other 1/4-20 x 3/4 inch screws,
nuts and lockwashers provided and secure the
target.
2. Slide the alignment scope (packed between the
plates of the mount) marked “R” onto the grooved
bracket of the mount marked “R”. Roughly center
the alignment scope on the bracket and firmly
tighten the scope mount clamp screws. Repeat
for the scope and mount marked “T”. Be sure to
match the serial number of the scope to the serial
number of the mount.
NOTE
Do not discard the protective end caps for the
scopes. They should be replaced when optical
alignment has been completed.
7 95-8400
DC POWER SUPPLIES
OPTICAL FILTER
THERMOELECTRICALLY
COOLED PHOTODETECTOR
FILTERWHEEL MOTOR
STATUS RELAY
REAR PANEL PC BOARD
CONNECTOR/RELAY PC BOARD
OPTIONS PC BOARD
SIGNAL CONNECTOR
POWER CONNECTOR
IR LENS
IR WINDOW
FILTERWHEEL
REAR PANEL PC BOARD
PREAMP GAIN CONTROL
AGC/TE COOLER PC BOARD
PREAMPLIFIER
PC BOARD
SYNC PICKOFF
A1396
DUAL RATIO PC BOARD
Figure 3—Location of Receiver Boards and Assemblies
8
CROSSHAIR ADJUSTMENTS (2)
A1397
SCOPE LAMP SCREWS (2)
12"
14"
4 3/8"
ALIGNMENT TARGET
ALIGNMENT SCOPE
SCOPE RECEIVER BRACKET
14 1/4"
TILT
ADJUSTMENT KNOB
ASSEMBLY
PAN
ADJUSTMENT KNOB
ASSEMBLY
LOCKING KNOB
ASSEMBLY
U-BOLTS (2)
USER-SUPPLIED
MOUNTING PIPE, 4 1/2 O.D.
PROTECTIVE CAPS (2)
FOOT BASE
FRONT VIEW SIDE VIEW
FOOT BASE
Figure 4—Pan Tilt Mount
18 MAX.
22 MAX.
17 MAX.
FRONT VIEWSIDE VIEW
A1398
ZERO
OUTPUT
OPERATE
ALIGN
TEST
O
V
mA
LO
MID
HI
CALIBRATION
ADJUSTMENT
SET-
POINT
RATIO DENOM NUM
MODE
SENSITIVITY
VAPOR ALARM
OUTPUT
SIG GND OUT OPT
OUTPUT
SELECT
SPARE
FUSE
1 A
FUSE 1 A
ADJUST
U-BOLTS AROUND POST
4.5
15 MAX.
SINGLE PURGE
HOLE LOCATED
ON CENTERLINE
AND 4.5" FROM
BACK OF INST.
(1/2 - 14 NPT)
USER SUPPLIED POST
4.6 MAX O.D.
3.5 MIN O.D.
CENTERLINE
+/– 5 DEGREES
TO THE VERTICAL
ALIGN
TO
OPPOSITE
HOUSING
JUNCTION BOX
ALL ELECTRICAL CONNECTIONS
ARE MADE WITHIN THIS BOX.
CUT-AWAY VIEW
OF TERMINAL BLOCK SHOWN
3/4 NPT
FOR 115 VAC
60 HZ
WIRING TO INST.
3/4-14 NPT
FOR LOW VOLTAGE
WIRING TO INSTRUMENT
Figure 5—Detector Mounting
INITIAL SETUP
When the inspection procedures and special precautions detailed above have been carefully observed,
the initial setup of the PW9200 is accomplished by following Steps 1 through 9 below:
NOTE
Signal ground of the electronics is not tied to the
housing case and therefore, is not tied to earth
ground. Optimum immunity to 60 cycle noise
could require tying signal ground to earth ground
external to the instrument.
CAUTION
Do not remove protective window covers until
Step 7. Do not mount the instrument until power
is available. In order to minimize the possibility
of condensation forming inside the instrument,
once mounted, the instrument should not be left
without power for extended periods of time.
1. Attach the pan-tilt mounts to a user supplied 4.5
inch O.D. mounting pipe with the two U-bolts supplied. Tighten the U-bolts securely at the desired
height.
2. Attach the transmitter and the receiver to the pantilt mounting plates using the 3/8-16 x 1-1/2 inch
stainless steel bolts, nuts and washers provided
with the instrument, as shown in Figure 5. Be sure
to attach the receiver to the mount marked “R” and
to attach the transmitter to the mount marked “T”,
and to match the serial number of the instrument
with the serial number of the mount. The mounting
surface should be vertical with the transmitter and
receiver roughly facing each other.
3. Connect external wiring as shown in Figure 6. Strip
the insulation back 1/4 inch. Insert the stripped
wire into the terminal under the appropriate number. Tighten the screw above the number by turning it clockwise using a screwdriver with a 1/8 inch
blade. All terminals in the junction box are numbered. Low voltage signal lines and high voltage
power lines from the junction box should be in separate cables, if possible. If the signal and power
lines are not in separate cables, the high voltage
power wires (115 vac line and power ground) must
be shielded from the signal lines for safety reasons. Any conduit installed must be of a flexible,
explosion-proof type, which will allow panning and
tilting of the housings for optimum alignment.
RATIO, NUMERATOR AND SIGNAL GROUND
wiring from the junction box should be connected
to external readout devices of at least 5,000 ohms
impedence. If 4 to 20 ma output is installed,
external readout devices must have less than 500
ohms impedence.
9 95-8400
Figure 6—System Interwiring Diagram
WARNING
If both conduit entrances to the junction box are
not used, the unused entrance must be fitted
with an explosion-proof pipe plug with at least
five full threads engaged.
4. Connect HYDROCARBON ALARM relay and STATUS ALARM relay signal terminals (4, 5, 6 and 7)
to external readout devices (e.g., indicator lamps,
alarm buzzers, motors, computer interface, etc.).
The hydrocarbon alarm relay contacts open when
a preset concentration of hydrocarbon vapor is
exceeded. The status alarm relay contacts open
when an obstruction or instrument failure is
detected.
5. Connect transmitter and receiver to the power
source. DO NOT apply power.
6. Be sure that the cover bolts are tight. Check
tightness of junction boxes and window assemblies.
7. Remove protective window covers from both the
transmitter and the receiver. Do not discard.
8. As power is first applied to the instrument, the
transmitter lamp should light and a faint rotation
noise may be heard within the receiver housing.
9. Allow at least one hour warmup time with the
instrument operating continuously before proceding to alignment.
NOTE
The instrument is designed for continuous operation. Excessive application and disconnection of
power to the transmitter will shorten the life of the
lamp.
OPTICAL ALIGNMENT/
SIGNAL STRENGTH
NOTE
The cross hairs of the alignment scopes have
been factory set for alignment of the transmitter
and receiver. If a mirror is used with the
PW9200, a special alignment procedure is provided in the APPENDIX.
IMPORTANT
Optimum alignment must be maintained to
ensure reliable operation of the instrument. If the
instrument is misaligned, the RATIO output will
be noisy and erratic.
After the instrument has been operating continuously
for at least one hour, alignment of the transmitter and
receiver is best accomplished as follows:
1. Adjust the locking knob assembly on the back
plate of each mount so that the end of the shaft is
at least 1-1/2 inch from the front plate. (See
Figure 4 for illustration of the pan-tilt mount.)
2. With the transmitter and receiver roughly facing
each other, view the alignment target attached to
the receiver mount through the alignment scope
attached to the transmitter mount. Adjust the pan
and tilt of the transmitter housing until the cross
hairs of the transmitter alignment scope are centered on the target attached to the receiver
mount.
3. Adjust the pan and tilt of the receiver housing until
the cross hairs of the receiver alignment scope
are centered on the target attached to the transmitter mount.
4. Remove the receiver window assembly by rotating counterclockwise. Avoid touching the window
with bare hands. Move the window assembly to a
safe place, being careful not to scratch the window.
5. Set the MODE selector switch on the front panel
to the ALIGN position.
6. Using the test jacks on the front panel, connect a
digital voltmeter (with a resolution of at least 1
MVDC) between the NUMERATOR (blue) and
SIGNAL GROUND (green).
NOTE
All voltage readings must be taken with a dc
voltmeter with a 10 megohm input impedence. Use of other devices will give inaccurate readings.
If the NUMERATOR signal is greater than 100 mV,
proceed with fine alignment as described in Step
10.
7. If the NUMERATOR signal is less than 100 millivolts, gross alignment may be obtained by two
people working together. Replace the window
assembly. One person should remain at the
receiver to adjust the pan and tilt of the housing.
The second person should stand at a distance of
about six feet from and facing the receiver and
sight the reflection of the transmitter lamp in the
receiver window. (Be careful to stand slightly to
one side of the beam path, so that the beam is
unobstructed.) The first person should adjust the
pan and/or tilt of the receiver until the reflection of
the transmitter lamp is visible on the receiver window. The second person should gradually back
away from the receiver, keeping the reflection
centered through pan and tilt adjustments until
10
the reflection is visible in the receiver window
when standing at the transmitter.
8. Remove the window assembly and check the signal at the NUMERATOR test jack (blue) on the
digital voltmeter. If the signal is greater than 100
millivolts, proceed with fine alignment as
described in Step 10.
9. If the NUMERATOR signal is still less than 100
millivolts, gross alignment can be obtained by
scanning the receiver. Set the pan adjustment of
the receiver to one side as far as it will go by turning the pan knob fully clockwise. Beginning with
the tilt adjustment set as far up as it will go (tilt
knob fully clockwise). Slowly move the tilt of the
receiver down as far as it will go by turning the tilt
knob counterclockwise. Watch for a sharp
increase in the signal strength (greater than 50
mV on the digital voltmeter). Change the pan of
the receiver by moving the pan knob a quarter
turn clockwise. Slowly move the tilt from bottom
to top. Repeat this scanning procedure until the
digital voltmeter indicates a NUMERATOR signal
greater than 100 millivolts.
10. Make small adjustments in the receiver pan and
tilt to maximize the amplitude of the NUMERATOR
voltage.
11. Make small adjustments in the transmitter pan
and tilt to maximize the amplitude of the NUMERATOR voltage at the receiver.
12. Move the high lead of the voltmeter to the RATIO
test jack (brown) on the front panel and read the
output voltage. The RATIO voltage should be 0.1
± 0.1 vdc. If the output is not within this range,
adjust the OUTPUT ZERO potentiometer on the
front panel to bring the voltage within the desired
range. Clockwise turns will increase and counterclockwise turns will decrease the RATIO output
voltage.
13. Replace the receiver window assembly and read
the NUMERATOR voltage at terminal 3 in the
junction box. The NUMERATOR output obtained
should be between 0.3 vdc and 0.5 vdc. If the
NUMERATOR output is within this range, proceed
to Step 15. If the NUMERATOR output obtained
exceeds 0.5 volts or is less than 0.3 volts after following all steps of the Optical Alignment/Signal
Strength procedure, the preamplifier gain must be
adjusted as described in Step 14.
14. To adjust the preamplifier gain, follow the Access
to Internal Components procedure (see
“Maintenance” section) and locate the preamplifi-
er P.C. board within the heat sink fins. The
preamplifier gain adjustment potentiometer is
located on the preamplifier P.C. board and can
be reached by inserting a screwdriver between
the fins from the bottom of the heat sink (as
viewed when the housing cover is open, but
attached to the housing by its hinges).
If the NUMERATOR output voltage is less than 0.3
vdc, turn the preamplifier gain potentiometer
clockwise. If the NUMERATOR output voltage is
greater than 0.5 vdc, turn the preamplifier gain
potentiometer counterclockwise.
15. Once optimum alignment has been obtained,
carefully adjust the locking knob assembly on the
back of each mount so that the end of the shaft
just makes contact with the back of the front
plate. DO NOT over tighten the locking knob
assembly.
16. View the target attached to the transmitter mount
through the receiver alignment scope to verify
that the cross hairs are centered on the target. If
the cross hairs are not centered and optimum
alignment is verified, adjust the cross hairs to
center on the target using the adjustment knobs
provided on the scope. Replace the protective
end caps on the alignment scope.
17. Repeat Step 16 for the transmitter alignment
scope.
NOTE
Optimum alignment must be accurately maintained to ensure proper operation of the instrument. Careful adjustment of the alignment scope
cross hairs will enable verification of alignment
accuracy.
18. Recheck that the NUMERATOR output has not
been affected by steps 15 through 17.
19. Remove the receiver window assembly and return
the MODE selector switch on the front panel to
the OPERATE position. Replace the window
assembly.
OPERATION/PERFORMANCE CHECK
NOTE
All voltage readings must be taken with a dc voltmeter with a 10 megohm input impedence. Use
of other devices will give inaccurate readings.
Proper operation should be verified periodically by
performing the checks and tests described below:
11 95-8400
ALIGNMENT
View the transmitter through the receiver alignment
scope to verify that the cross hairs of the scope are
centered on the target attached to the transmitter
mount. If the cross hairs are not centered on the target, alignment has changed. Adjust the pan and/or
tilt of the receiver until the cross hairs of the alignment
scope are centered on the target. Check the transmitter alignment scope to verify that the cross hairs are
centered on the target attached to the receiver mount.
If not centered, adjust as with the receiver.
NOTE
Accurate alignment must be maintained for reliable operation of the instrument. If alignment is
changing, the vertical mounting pipe may not be
sufficiently stable, or it is being moved during
operation. This problem must be corrected to
ensure that alignment is maintained.
SIGNAL STRENGTH
The NUMERATOR output read from terminal 3 in the
junction box should be between 0.3 vdc and 0.5 vdc.
If the NUMERATOR voltage is less than 0.3 volts,
realign the instrument as described in the “Optical
Alignment/Signal Strength” procedure. If the NUMERATOR output obtained exceeds 0.5 volts, the preamplifier gain must be adjusted as described in Step 14
of the “Optical Alignment/Signal Strength” procedure.
OUTPUT ZERO
The OUTPUT ZERO (RATIO) is factory set for hydrocarbon-free air. The OUTPUT ZERO should be
checked periodically and the ZERO potentiometer
should be adjusted when necessary.
1. With the instrument viewing hydrocarbon-free air
and both transmitter and receiver windows in
place, record the RATIO voltage at the junction
box. If the RATIO voltage is not 0.1 ± 0.1 vdc, the
OUTPUT ZERO potentiometer should be adjusted
as described in the following steps.
2. Remove the receiver window and locate the OUTPUT ZERO potentiometer on the front panel.
3. If the RATIO voltage recorded in step 1 was higher than 0.1 ± 0.1 vdc, rotate the ZERO potentiometer counterclockwise until the RATIO voltage
is within the desired range.
4. If the RATIO voltage recorded in Step 1 was lower
than 0.1 ± 0.1 vdc, rotate the ZERO potentiometer
clockwise until the RATIO output is within the
desired range.
HEAVY HYDROCARBON RESPONSE
CONFIDENCE TEST
To verify that the instrument is responding to the presence of heavy hydrocarbon vapor in the path:
1. With power applied to the instrument, connect a
digital voltmeter between the RATIO (brown) and
SIGNAL GROUND (green) test jacks on the front
panel.
2. Hold a piece of clear plastic (roughly 8 mils thick)
in the path of the light beam. Be careful not to
block the beam with anything other than the plastic film.
3. The RATIO voltage should increase sharply. If
the RATIO voltage does not increase, contact the
factory for assistance.
4. Repeat Steps 1 and 2 and check the resistance
between terminals 6 and 7 in the receiver junction
box. The resistance should increase from zero to
infinity.
STATUS ALARM CONFIDENCE TEST
To verify that the instrument status alarm circuit is
working properly:
1. With power applied to the instrument, block the
beam with an opaque object.
2. The Status Alarm should activate within 120 seconds. The resistance between terminals 4 and 5
in the receiver junction box should increase from
zero to infinity. If the status alarm does not activate, contact the factory for assistance.
INSTRUMENT OUTPUT
The 0 to 10 vdc RATIO output is available on all
PW9200 instruments at the RATIO test jack (brown)
on the front panel and at the receiver junction box
when the OUTPUT SELECT switch is set to position V.
An optional 4 to 20 ma output can be ordered with the
instrument or can be field installed at any time after
purchase. The 4 to 20 ma output option converts the
standard 0 to 10 vdc RATIO output to a 4 to 20 ma
output. If installed, the 4 to 20 ma output will be available at the receiver junction box when the OUTPUT
SELECT switch on the front panel is set to the MA
position. The 4 to 20 ma current may be tested by
opening the user installed RATIO wire in the junction
box (terminal 1) and connecting a current meter
between the RATIO wire and terminal 1. The 4 to 20
ma output will drive a user supplied load of 0 to 500
12
ohms. The 4 to 20 ma output is surge protected.
The RATIO output in this manual is indicated in 0 to
10 vdc. For instruments using the 4 to 20 ma output,
the standard 0 to 10 vdc output can be read at the
RATIO test jack (brown) on the front panel or at the
receiver junction box when the OUTPUT SELECT
switch is set to the V position. In addition, a voltage
to current transfer curve is provided. See Figure A2.
CALIBRATION
The PathWatch system involves “line” rather than
“point” detection, monitoring the path between the
transmitter and the receiver. The instrument’s measurement is a function of the gas concentration
(expressed in ppm) times the length of the path or
cloud (expressed in meters). Thus, the instrument’s
calibration is in units of PPM-Meters (PPM-M).
Because it is an open path system, the instrument’s
output reflects the average concentration over the
entire path length.
Simulated gas clouds and controlled gas concentrations are used to factory calibrate the PW9200. The
response of a typical instrument is plotted on calibration graphs, which are included in the APPENDIX. A
calibration tube and a specified concentration of gas
can be used to check the instrument’s calibration
against the graph. The calibration graph is used to
determine the average ppm concentration in the
operational path length.
CALIBRATION EQUIPMENT
The optional calibration equipment for the PW9200 is
illustrated in Figure 7.
(1) Calibration Adapter
(1) Calibration Tube with flowmeter and hoses
If calibration equipment is not purchased, contact the
factory for calibration equipment or service.
PROCEDURE
The calibration of the instrument should be routinely
checked at least every twelve months, when there has
been a change in the type of hydrocarbon being
monitored, or when the operating path is changed
significantly. The instrument should be installed,
aligned and operating for at least one hour before
checking the calibration. This procedure is best performed by two people.
NOTE
In order to ensure accurate calibration, this procedure should be accomplished when the path is
known to be free of hydrocarbon vapors.
13 95-8400
TRANSMITTER
MOUNTING SCREWS (4)
FLOWMETER INLET HOSE (5 1/2 FT)
FLOWMETER OUTLET HOSE
CALIBRATION ADAPTER
VENT HOSE (5 1/2 FT)
INFRARED TRANSMITTING WINDOW
CALIBRATION TUBE
FLOWMETER
REGULAT OR V AL VE
CALIBRATION GAS CYLINDER
Figure 7—Calibration Equipment
1. Attach the Flowmeter Outlet Hose to the appropriate hose fitting on the Calibration Tube as shown
in Figure 8.
2. Remove the two protective caps from the
Calibration Tube. To make certain that it is completely free of any residual hydrocarbon vapors,
purge the Calibration Tube with oil-free compressed air at no more than 5 psi and 10 SCFH
for 2 minutes. Do not block the vent. Do not
pressurize or evacuate the calibration tube while
purging.
3. Remove the receiver window assembly. Set the
MODE switch on the front panel to the OPERATE
position. If 4 to 20 ma output option is used, set
the OUTPUT SELECT switch on the front panel to
V and break the connection at the junction box
between the RATIO output (terminal 1) and its
field wire to remove the current load.
4. Install the Calibration Adapter on the transmitter
window mounting ring with the four 10-32 x 3/4
inch screws provided with the adapter.
5. Insert the calibration tube into the adapter, so that
the flowmeter is vertical on the right side of the
tube. Make sure that the tube is seated squarely
and securely in the adapter.
6. Attach the vent hose and flowmeter inlet hose to
the calibration tube as shown in Figure 8. For
heavier than air gases, the flowmeter outlet hose
is connected to the hose fitting on the bottom of
the calibration tube and the vent hose is connected to the hose fitting on the top. For lighter than
air gases, these two connections are reversed.
7. Adjust the OUTPUT ZERO potentiometer on the
receiver until the RATIO voltage is 0.1 ± 0.1 vdc.
8. Attach the calibration gas cylinder to the flowmeter inlet hose, making sure that the regulator is
shut. At the junction box, attach a digital voltmeter with a resolution of at least 1 millivolt dc
between the RATIO output (terminal 1) and SIGNAL GROUND (terminal 2).
WARNING
DO NOT pressurize or evacuate the calibration
tube. Make sure vent hose is not blocked or
crimped.
9. With the gas cylinder regulator set at no more
than 2 psi, open and adjust the regulator and flow
meter valves so that the flow indicator on the calibration tube reads 5 SCFH.
10. Wait at least five minutes and observe the RATIO
output voltage. The reading should be within the
range indicated on the calibration graph. If the
RATIO output is not within the calibration range,
use the CALIBRATION ADJUSTMENT potentiometer on the front panel of the receiver to bring
the RATIO output within the desired range.
11. Close the gas regulator. Remove the flowmeter
inlet hose from the gas cylinder regulator.
12. Remove the calibration tube from the calibration
adapter and replace the protective end caps.
Remove the calibration adapter from the window
mounting ring.
13. With clean air present in the path, re-adjust the
OUTPUT ZERO potentiometer on the receiver so
that the RATIO voltage is 0.1 ± 0.1 vdc.
14. If the 4 to 20 ma output option is used, return the
OUTPUT SELECT switch on the front panel to the
MA position. Reconnect the RATIO field wire in
the junction box.
USE OF THE CALIBRATION GRAPH
The instrument output is related to the presence of
hydrocarbon vapor in the path in terms of a unit
called PPM-Meters (PPM-M). Because it is an open
path system, the instrument’s measurement is a function of the gas concentration (expressed in PPM)
times the length of the vapor cloud (expressed in
meters).
In interpreting the instrument’s output, two possible
conditions exist:
A. The hydrocarbon vapor cloud is larger than the
path length.
14
HOOK-UP FOR
LIGHTER-THAN-AIR GASES
HOOK-UP FOR
HEAVIER-THAN-AIR GASES
A
A
B
B
C
C
HOSE IDENTIFICATION
A. FLOWMETER INLET
B. FLOWMETER OUTLET
C. VENT
REAR VIEW OF CALIBRATION TUBE
(INSTRUMENT SIDE)
A1493
Figure 8—Calibration Hookup
B. The hydrocarbon vapor cloud is smaller than the
path length.
NOTE
If the cloud length cannot be approximated from
the installation parameters, it must be assumed
that the cloud length is equal to the path length.
The calibration graphs provided in the APPENDIX
correlate the RATIO output voltage to the PPM-M
product. To determine the average vapor concentration in the cloud or path, divide the PPM-M product by
the cloud or path length in meters.
For Example:
Condition A - Cloud larger than path, or cloud length
unknown. (Gas is propane, PathWatch
has Heavy HC filters. See Figure A6.)
Assume: - RATIO output of 2 vdc
- Path length of 50 meters
- (cloud is equal to path)
Read: Calibration Graph indicates
that 2 vdc output corresponds
to approximately 1000 PPM-M
Then: 1000 PPM-M ÷ 50 M
Result: 20 PPM average vapor con-
centration over the 50 meter
path.
Condition B - Cloud smaller than path
Assume: – RATIO output of 2 vdc
– Cloud length of 10 meters
Read: Calibration graph indicates
that 2 vdc output corresponds
to approximately 1000 PPM-M
Then: 1000 PPM-M ÷ 10M
Result: 100 PPM average vapor con-
centration over the 10 meter
cloud.
All factory calibrations are performed with the SENSITIVITY switch set in the HI position (maximum sensitivity).
HYDROCARBON VAPOR
ALARM THRESHOLD ADJUSTMENT
In critical applications, it is recommended that the
calibration be checked before setting the alarm
threshold. Based on the specific application of the
instrument, select the concentration in ppm at which
the Hydrocarbon Vapor Alarm will activate. It is
important to remember that the open path detector
measures the average gas concentration over a continuous series of points along a path. Because the
gas concentration over a 100 to 300 foot path could
vary from only a few ppm to explosive levels and
because the user must know when the gas concentration at any location along the path is approaching
an explosive level, the threshold must be set at a
much lower level than a point detector. Typically, the
open path detector is set to alarm for an average concentration in the 0.05% to 0.10% LFL range for heavy
hydrocarbons.
To determine the equivalent RATIO output (volts) for
the selected concentration (ppm), refer to the calibration graph provided in the APPENDIX.
1. Multiply the path length (M) by the selected vapor
concentration (PPM) to arrive at PPM-M.
NOTE
If the cloud length can be approximated from the
installation conditions, a more accurate result is
obtained by multiplying the CLOUD length (M) by
the selected vapor concentration (PPM) to arrive
at PPM-M.
2. From the calibration graph, read the equivalent
RATIO output voltage for the PPM-M product
determined in Step 1.
To set the hydrocarbon vapor alarm threshold:
3. Attach a digital voltmeter between the HC ALARM
SETPOINT jack (grey) and SIG GND (green) on
the front panel of the receiver.
4. Adjust the HC ALARM ADJUST potentiometer on
the front panel so that the Hydrocarbon Alarm set
point voltage matches the RATIO output determined from the calibration graph in Step 2,
above.
15 95-8400
Section 3
Maintenance
GENERAL PRECAUTIONS
As with all precision electro-optical equipment, care
must be taken to avoid sharp blows to the instrument.
Do not drop it or allow heavy objects to strike it. Do
not touch the windows, lenses, lamps, filters or other
optical surfaces with bare hands. Customary precautions for the use of explosion-proof instrumentation in
hazardous environments should be observed. Ensure
that no hazardous vapor conditions exist in procedures where either the cover, window assembly or
junction box are to be opened when circuits are alive.
WARNING
Live line voltage is exposed at several points
within the PW9200. This is potentially dangerous and contact by maintenance personnel must
be avoided.
The threads of the housing cover and window assembly are lubricated to eliminate the possibility of seizing. The threads should be checked periodically and
lubrication should be added when necessary. When
adding lubrication to the threads, care must be taken
to ensure that the lubrication does not touch the window surface.
GENERAL INFORMATION
The receiver electronics are comprised of six printed
circuit boards and electrical wiring and components
located on the receiver baseplate and the motorbox.
Two of the printed circuit boards are permanently
mounted and the other four are easily removed and
replaced as indicated below:
P.C. BOARD PERMANENT/REMOVABLE
Preamplifier permanent
AGC/TE cooler removable
Synchronous demodulator removable
Rear panel removable
Options removable
Connector/Relay permanent
The receiver functions described in Section 1 and
Figure 1 of this manual are located on a printed circuit
board or assembly as shown below:
RECEIVER FUNCTION LOCATION
Infrared Photodetector Detector/Preamp
assembly
Sync Circuitry Rear panel p.c. board
and sync demod p.c.
board
Amplifier Preamp p.c. board
and sync demod p.c.
board
Signal Processing Electronics AGC/TE cooler and
sync demod p.c.
board
Ratiometer Rear panel p.c. board
Threshold Detector Rear panel p.c. board
OR Gate Function Connector/relay p.c.
board
Obstruction/Status Alarm Relay Connector/Relay p.c.
board
Adjustable Threshold Detector Rear panel p.c. board
HC Alarm Set Rear panel p.c. board
(accessed from front
panel)
HC Vapor Alarm Relay Connector/Relay p.c.
board
4 to 20 mA Converter 4 to 20 ma output p.c.
board
Assemblies and printed circuit boards are available
as spare parts. To facilitate troubleshooting and corrective maintenance of the PW9200, users are
advised to stock LEVEL ONE and LEVEL TWO from
the “Recommended Spare Parts List.”
ACCESS TO INTERNAL
COMPONENTS
All internal components of the transmitter and receiver
are mounted to the cover of the housing (see Figure
3). Access to these components is obtained either by
swinging open the cover on its hinges or by removing
the cover and associated components from the housing.
1. Disconnect all power to the instrument.
2. Remove the 20 bolts that hold the cover to the
housing.
3. Swing open the cover to permit access to the
connector(s). DO NOT OPEN the receiver cover
more than three inches to prevent undue stress
on the connector(s). The transmitter cover will
open more than three inches.
16
4. Disconnect the connector plug(s) from the receptacle(s). The transmitter has one connector and
the receiver has two connectors. The instrument
can be inspected or serviced on-site while the
cover is opened and attached by its hinges. If
service is to be performed off-site, the cover and
attached components can be removed from the
housing as described in Step 5.
5. With the cover swung open, lift up to disengage
the hinges. Care must be taken to avoid scratching the flanges or damaging the internal components.
Each time the instrument housing is opened for maintenance, the desiccant pack should be checked.
When the desiccant pack is expanded only slightly,
no change is necessary. If the desiccant is expanded to twice or more of its original size, the desiccant
should be replaced. Extra desiccant packets are
available from Detector Electronics (see
“Recommended Spare Parts List.” DO NOT replace
the desiccant until all other maintenance procedures
have been completed. Remove the old desiccant by
cutting the strings that attach it to the power supply
wiring. Remove the plastic bag on the replacement
packet and tie it to the power supply wiring. Be sure
that the desiccant packet is securely attached to the
power supply wiring so that it cannot come loose
inside the housing. Close the cover immediately after
replacing the desiccant.
To reattach the cover to the instrument housing:
1. Holding the cover completely open, slide the
cover pins onto the housing hinges. Do not tighten the hinge screws.
2. If necessary, replace the desiccant pack.
3. Reconnect the plug(s) and receptacle(s) in the
housing and close the cover. Guide the cable to
ensure that it is not pinched.
P.C. BOARD AND ASSEMBLY
REPLACEMENT
(See Figure 3 for locations)
SYNCHRONOUS DEMODULATOR AND OPTIONS
P.C. BOARDS
The sync demod board is located to the right and the
options board is located to the left of the filterwheel
motor inside the motorbox. Remove either board by
pulling it out of its connector on the rear panel p.c.
board and sliding it through the card guides out of the
motorbox. To replace the sync demod or options
board, make sure that the notch on the board matches the key in the connector and slide the board along
the card guides into the motorbox. Make sure that
the board is seated firmly in the connector.
REAR PANEL P.C. BOARD
The rear panel p.c. board is attached to the side of
the motorbox next to the connector/relay p.c. board.
The sync demod and options boards must be
removed before the rear panel board can be
removed.
To remove:
1. On the connector/relay p.c. board, remove the
STATUS ALARM and HC ALARM relays from their
sockets.
2. Release the ribbon connector that connects the
rear panel board to the connector/relay board.
3. Remove the six sockethead screws that hold the
rear panel board to the motorbox tabs.
4. Pull the top of the rear panel board away from the
motorbox to release the two connectors at the top
of the board.
5. Being careful not to touch the sync pickoff with
the filterwheel, remove the board.
To replace:
1. Being careful not to touch the sync pickoff with
the filterwheel, slide the board into place.
2. Firmly press the connectors at the top of the
board into the mating connectors on the motorbox.
3. Attach and lock the ribbon connector to the connector/relay p.c. board.
4. Replace the six socket head screws that hold the
rear panel board to the motorbox tabs.
5. Replace the STATUS ALARM and HC ALARM
relays in their sockets on the connector/relay p.c.
board.
AGC/TE COOLER P.C. BOARD
The AGC/TE cooler board is mounted in the detector/preamp assembly within the fins of the heat sink.
17 95-8400
To remove:
1. Release the ribbon connector that connects the
AGC/TE cooler board to the preamplifier board,
which is permanently attached to the bottom of
the heat sink.
2. Holding the ribbon connector to the side, pull the
AGC/TE cooler board so that the connector to the
motorbox disengages. Slide the board out of the
heat sink fins.
To replace:
1. Position the board so that the two parts of the
connector to the motorbox are lined up.
2. Holding the ribbon connector to the side, slide the
board into the fins of the heat sink as far as it will
go so that the connector to the motorbox
engages.
3. Attach and lock the ribbon connector from the
preamplifier board.
DETECTOR/PREAMP ASSEMBLY
The detector/preamp assembly is comprised of the
infrared photodetector mounted inside a baffle, an
optical filter, the heat sink and the permanently
mounted preamplifier p.c. board. The detector/
preamp assembly is located on the top of the motorbox beside the power supplies.
NOTE
Exposure to direct light (particularly fluorescent
light) can cause permanent damage to the
infrared photodetector. Care should be taken to
avoid exposing the photodetector to light when
the detector/preamp assembly is removed from
the instrument.
To remove:
1. Remove the four 6-32 sockethead screws that
hold the assembly to the motorbox.
2. Lift the assembly up until the baffle clears the
motorbox.
To replace:
1. Position the assembly over the motorbox so that
the connector and hole for the baffle are aligned.
2. Slide the assembly into place.
3. Replace the four 6-32 sockethead screws that
hold the assembly to the motorbox.
SYNC PICKOFF
The sync pickoff is mounted in a socket, which is
located in the center of the rear panel p.c. board.
The sync pickoff is removed by pulling if from the
socket. To replace the sync pickoff, install with the
red dot up (toward the motorbox connectors).
SCHEDULED MAINTENANCE
It is recommended that the following maintenance
procedures be performed periodically as described:
Maintenance Procedure Interval
12 mo. 24 mo.
Clean exterior optical components X
Clean interior optical components X
Replace filterwheel motor X
Replace 15 watt lamp X
Calibration check X
Replace desiccant X
CLEANING OF OPTICAL COMPONENTS
Exterior (12 month interval)
Due to the gradual accumulation of dust, chemical
deposits or other foreign matter, the exterior optical
surfaces must be cleaned every twelve months. In
some applications, cleaning of the windows may be
required more frequently. The need for cleaning can
usually be detected by a gradual decrease in the
NUMERATOR and DENOMINATOR output signals
and/or by visual inspection of the optical surfaces.
1. Disconnect all power to the instrument.
NOTE
If possible, direct a flow of clean, oil-free compressed air onto the optical surfaces before and
after cleaning.
2. Clean the outer surfaces of the transmitter and
receiver windows with clean cotton swabs and
alcohol. Finish with clean optical tissue. DO NOT
TOUCH the windows or other optical surfaces
with bare hands.
3. Reconnect the instrument and re-apply power.
Interior (24 month interval)
Interior optical components (inside surface of window,
lens, filters and sync pickoff) should be cleaned every
two years. Although it is possible to perform all these
procedures on-site, a lab environment is preferable
as it is cleaner and easier to work in. (See “Access to
Internal Components.”)
18
WINDOWS
Interior windows are reached by removal of the transmitter and receiver window assemblies. Clean as
described in “Exterior optical cleaning” procedure
above.
LENS, SYNC PICKOFF AND OPTICAL FILTERS
1. Remove the motor and filterwheel following
“Replacement of Filterwheel Motor” procedure.
2. The lens is located in the center of the receiver
baseplate. Using clean cotton swabs and alcohol, clean both sides of the lens. Finish with clean
optical tissue.
3. The sync pickoff is located at the center of the
rear panel p.c. board on the inside of the motorbox. The optical surfaces are located on the
inside of the U-shaped device. Using clean cotton swabs and alcohol, clean both optical surfaces of the sync pickoff. Remove any excess
alcohol and completely dry the surfaces with
clean, dry cotton swabs.
4. The optical filters are located in the filterwheel,
which is attached to the motor shaft. Clean both
sides of each filter using clean cotton swabs and
alcohol. Finish with clean optical tissue.
REPLACEMENT OF FILTERWHEEL MOTOR
(12 Month Interval)
It is recommended that this procedure be performed
in a lab environment. (See ACCESS TO INTERNAL
COMPONENTS.) Cleaning of interior optical components should be done after the filterwheel motor is
removed.
1. The receiver housing cover and internal components should be placed so that the open side of
the motorbox faces the technician. The assembly
should be securely propped during this procedure to avoid damage to the internal components.
2. Disconnect motor connectors.
3. While holding the motor still, remove the four 6-32
sockethead screws on the front panel that attach
the motor and standoffs to the front panel.
4. Avoiding contact with the sync pickoff on the rear
panel p.c. board, carefully slide the motor and
attached filterwheel out of the motorbox. Viewing
ports have been provided on each side of the
motorbox to permit visual inspection of the position of the filterwheel relative to the sync pickoff.
5. Remove the nut that holds the hub to the filterwheel and detach the filterwheel from the hub.
DO NOT TOUCH filters with bare hands.
6. Remove the nut from the replacement motor hub
and slide the filterwheel onto the replacement
motor shaft. Make sure that the side of the filterwheel with the filter retaining rings/fan blades is
facing toward the body of the motor. Replace the
nut, using low strength thread locking compound
on the threads of the hub. Make sure the compound is thoroughly dried before rotating the filterwheel.
7. Replace the motor/filterwheel assembly ensuring
that the filterwheel edge is straddled by the sync
pickoff. Check that the filterwheel does not come
into contact with the sync pickoff during rotation.
8. Replace the four sockethead screws that hold the
motor to the back of the instrument front panel.
Reconnect motor connectors.
REPLACEMENT OF TRANSMITTER LAMP
(Variable Interval)
The 15 watt lamp used in the PW9200 should be
replaced at a 24 month interval.
WARNING
Do not inspect the transmitter while the lamp is
operating. To avoid possible eye damage, disconnect instrument power before checking.
To replace the transmitter lamp, use the following procedure:
1. Disconnect all power to the instrument.
2. As an additional precaution, disconnect power
wires at the junction box.
3. Remove the window assembly from the transmitter housing by rotating counterclockwise (CCW).
DO NOT TOUCH the window with bare hands.
4. Move the window assembly to a safe place, being
careful not to scratch the window.
5. Remove the old lamp by pulling it out of the lampholder. DO NOT TOUCH the transmitter reflector with bare hands.
6. Insert the new lamp by pushing it into the lampholder, aligning the pins and holes in the lamp
socket and gently wiggling until it is held firmly by
the two clamps. Replacement lamps are available from the factory. (See “Recommended
Spare Parts List”.)
19 95-8400
NOTE
DO NOT TOUCH the lamp envelope with bare
fingers. Use the lamp wrapper provided with the
new lamp, clean white gloves, or clean optical
tissue when inserting a new lamp. Also, be careful to avoid touching the inner surface of the
reflector.
7. Be sure that the lamp is centered in the reflector
and does not touch the edge of the reflector
opening. If the lamp is touching the reflector,
gently apply sideways pressure to bend the
lamp/socket assembly until it is no longer touching the reflector opening and is centered. Use
clean gloves, tissue, etc., and do not touch the
reflector surface or lamp envelope with bare
hands, since acid from the fingertips will etch the
lamp envelope and reduce the life of the lamp.
8. Replace the window assembly and tighten down
securely until at least five full threads are
engaged.
9. Check tightness of cover bolts and window
assemblies on both housings.
10. Reconnect power wires in the junction box.
11. Close and recheck tightness of junction box
cover.
12. Re-apply power.
13. Repeat “Optical Alignment” procedure.
TROUBLESHOOTING
For assistance in rectifying setup problems and simple malfunctions, consult the Troubleshooting Table
below.
SYMPTOM: Transmitter lamp does not light.
POSSIBLE CAUSE: No power to transmitter.
CHECK: Voltage into transmitter. Should be
nameplate voltage rating (±10%).
REMEDIAL ACTION: If wrong voltage, check
external fusing or defective power wiring
to transmitter.
POSSIBLE CAUSE: Fuse blown in transmitter.
CHECK: Fuse.
REMEDIAL ACTION: Replace fuse.
POSSIBLE CAUSE: Defective lamp.
CHECK: Voltage into transmitter before con-
cluding that lamp is defective.
REMEDIAL ACTION: See Replacement of
Transmitter Lamp procedure.
SYMPTOM: Transmitter lamp consistently burns
out before 6 months.
POSSIBLE CAUSE: Constant high line voltage.
CHECK: Voltage into transmitter. Should be
nameplate voltage rating (±10%).
REMEDIAL ACTION: Reduce power line volt-
age.
POSSIBLE CAUSE: Excessive vibration or shock
at the transmitter.
CHECK: Environment at transmitter.
REMEDIAL ACTION: Alter mechanical envi-
ronment at transmitter location with vibration isolators, etc.
POSSIBLE CAUSE: Repeated application and
removal of power to transmitter.
CHECK: History since installation.
REMEDIAL ACTION: Maintain power to the
instrument at all times.
SYMPTOM: Transmitter lamp lights, but no output
voltage on NUMERATOR (blue) relative to
GROUND (green) test jack.
POSSIBLE CAUSE: No power to receiver.
CHECK: Voltage into receiver. Should be
nameplate voltage rating (±10%).
REMEDIAL ACTION: If wrong voltage, check
external fusing and power wiring to
receiver.
POSSIBLE CAUSE: Fuse blown in receiver.
CHECK: Listen for faint sound of filterwheel
motor in receiver.
REMEDIAL ACTION: If filterwheel is not turn-
ing, replace fuse.
POSSIBLE CAUSE: Filterwheel motor failure.
CHECK: Is filterwheel rotating?
REMEDIAL ACTION: If filterwheel does not
rotate after replacing fuse, see
“Replacement of Filterwheel Motor” procedure.
POSSIBLE CAUSE: Transmitter and receiver not
properly aligned.
CHECK: Voltage on NUMERATOR (blue) test
jack when a flashlight or 60 watt light bulb
is held in front of receiver window.
Voltage should increase from zero.
REMEDIAL ACTION: Repeat Alignment pro-
cedure.
20
SYMPTOM: Voltage at NUMERATOR (blue) test
jack relative to GROUND (green) is not within
0.3 to 0.5 vdc after proper alignment and output zero adjustment.
POSSIBLE CAUSE: Improper preamplifier gain
setting for path length.
REMEDIAL ACTION: See Step 14 of “Optical
Alignment/Signal Strength” procedure.
SYMPTOM: RATIO is noisy or erratic.
POSSIBLE CAUSE: Instrument not optically
aligned.
CHECK: Voltage at NUMERATOR test jack.
Voltage should be 0.3 to 0.5 vdc.
REMEDIAL ACTION: If NUMERATOR voltage
is low, realign as described in “Optical
Alignment” procedure.
SYMPTOM: RATIO voltage is negative or 4 to 20
ma output is below 4 ma.
POSSIBLE CAUSE: The ZERO adjustment poten-
tiometer located on the front panel is not set
properly.
CHECK: Setting of ZERO potentiometer.
REMEDIAL ACTION: Adjust ZERO poten-
tiometer until RATIO output is 0.1 ± 0.1
vdc.
POSSIBLE CAUSE: Instrument malfunction.
CHECK: NUMERATOR and DENOMINATOR
voltages when a bare flashlight bulb or
bare 60 watt light bulb is held in front of
receiver window.
REMEDIAL ACTION: Replace each printed
circuit board (one at a time) and recheck
voltages. Contact factory if fault cannot
be located.
SYMPTOM: RATIO voltage is steady and does not
appear to be responding to heavy hydrocarbons within the monitored path.
POSSIBLE CAUSE: Malfunction of signal pro-
cessing circuitry.
CHECK: Response of RATIO when a piece of
plastic film (roughly 8 mils thick) is placed
in front of the receiver window. The
RATIO voltage should increase to at least
+2 vdc.
REMEDIAL ACTION: Substitute spare boards
and assemblies until defective part is
located and RATIO responds properly to
plastic film. Defective part can be
returned to factory for analysis and repair.
POSSIBLE CAUSE: Object in beam.
REMEDIAL ACTION: Remove obstruction.
SYMPTOM: HC Alarm does not activate when
hydrocarbon vapors are present in monitored
path, or HC Alarm activates too often.
POSSIBLE CAUSE: Improper HC Alarm threshold
setting.
CHECK: Voltage at HC ALARM SETPOINT
jack relative to GROUND. Refer to
Calibration graph in APPENDIX for concentration indicated by alarm threshold
setting.
REMEDIAL ACTION: Adjust setpoint if
required. See “Hydrocarbon Vapor Alarm
Threshold Adjust-ment” procedure.
POSSIBLE CAUSE: Malfunction of HC Alarm cir-
cuitry.
CHECK: RATIO voltage relative to voltage on
HC ALARM SETPOINT jack. If RATIO
voltage exceeds alarm setpoint and alarm
does not activate, a malfunction of alarm
circuitry exists.
REMEDIAL ACTION: Replace rear panel p.c.
board and HC alarm relay on
connector/relay board.
SYMPTOM: RATIO output obtained during calibra-
tion check is not within the range indicated by
the calibration graph.
POSSIBLE CAUSE: Excessive hydrocarbon
background at installation site.
CHECK: Hydrocarbon background along
instrument path length with an independent hydrocarbon vapor analyzer.
REMEDIAL ACTION: Wait until hydrocarbon
background along path length of instrument is low, then recheck calibration.
POSSIBLE CAUSE: Calibration shift after factory
calibration due to some parameter within the
instrument, or to some change in the installation parameters.
CHECK: Calibration to be sure that calibra-
tion check was performed properly and
calibration point obtained is repeatable.
REMEDIAL ACTION: If calibration check is
repeatable and not within calibration
range, adjust CALIBRATION ADJUSTMENT potentiometer on front panel with
calibration tube filled and installed.
21 95-8400
If malfunctions cannot be corrected by carefully following the procedures described in this manual, contact the factory for assistance. In many cases, sufficient information to correct the malfunction can be
provided over the telephone. If it is necessary to contact the factory by telephone, it is helpful to have the
operation and maintenance manual accessible and to
obtain the following readings for the service technician:
Instrument S/N ________________
Options purchased ______________________________
Measure and record the channel voltages under two
conditions:
1. Normal operating conditions
2. With the receiver window blocked with opaque
material (e.g. cardboard disk).
NORMAL BLOCKED
RATIO __________ vdc RATIO __________ vdc
DENOM __________ vdc DENOM __________ vdc
NUM __________ vdc NUM __________ vdc
HC alarm Setpoint __________ vdc
Path length __________ feet or __________ meters
Both field and factory service are available from
Detector Electronics. If it becomes necessary to
return an instrument to the factory, extreme care must
be taken in packing the instrument for shipment. The
monitor should be enclosed in a plastic bag, surrounded with at least two inches of foam or shipping
pellets on all sides and shipped in a heavy duty carton. Lack of sufficient cushioning can cause extensive damage to internal components. It is not usually
necessary to return the transmitter and, if carefully
packed, just the receiver housing cover and attached
components can be shipped.
DEVICE REPAIR AND RETURN
Prior to returning devices or components, contact the
nearest local Detector Electronics office so that a
Service Order number can be assigned. A written
statement describing the malfunction must accompany the returned device or component to expedite finding the cause of the failure.
Pack the unit or component properly. Use sufficient
packing material in addition to an anti-static bag or
aluminum-backed cardboard as protection from electrostatic discharge.
Return all equipment transportation prepaid to the
factory in Minneapolis.
ORDERING INFORMATION
RECOMMENDED SPARE PARTS
Description Qty Part Number
Level One (highly recommended)
Transmitter lamp (15 watt) 1 102642-001
Filterwheel motor (115 vac) 1 005618-001
One ampere fuse 5 107407-002
Alarm relay, 115 vac 2 102590-001
Desiccant pack 1 102669-001
Test power cable 1
Level Two (Recommended)
Sync demod p.c. board
Single channel 1 005586-001
Dual channel 1 005586-002
AGC/TE cooler p.c. board 1 005583-001
Rear panel p.c. board
Single channel 1 005595-001
Dual channel (standard) 1 005595-002
Dual channel (fast) 1 005595-003
Detector/preamp assembly 1 005580-001
4 to 20 ma p.c. board
Single channel 1 005592-001
Dual channel 1 005592-002
2 inch diameter lens 1 005616-001
For assistance in ordering a system to meet the
needs of a specific application, please contact:
Detector Electronics Corporation
6901 West 110th Street
Minneapolis, Minnesota 55438 USA
Operator: (952) 941-5665 or (800) 765-FIRE
Customer Service: (952) 946-6491
Fax: (952) 829-8750
Web site: www.detronics.com
E-mail: detronics@detronics.com
22
Appendix
This APPENDIX contains:
Optical Alignment Procedure for Installations Using a
Mirror
Receiver Interconnections
Voltage to Current Transfer Curve
Calibration Graphs of a Typical Instrument.
OPTICAL ALIGNMENT PROCEDURE
FOR INSTALLATIONS USING A MIRROR
After the Initial Setup procedures have been followed
and the instrument has been operating continuously
for at least one hour, alignment of the transmitter,
receiver, and mirror is best accomplished by two people using the following procedure:
1. Attach the mirror pan-tilt mount with U-bolts to the
user supplied 4.5 inch O.D. mounting pipe at the
desired height. Roughly set the mirror for the
appropriate angle, and securely tighten the Ubolt.
NOTE
The cross hairs of the alignment scopes have
been factory set for alignment of the transmitter
and receiver WITHOUT MIRRORS at the operating distance indicated in the Test Record. If this
separation distance is not the same as the actual
installation because mirrors are used, the cross
hairs of the alignment scopes will need to be
reset after the instrument is properly aligned.
IMPORTANT
Optimum alignment must be maintained to
ensure reliable operation of the instrument.
2. With the transmitter roughly facing the mirror, view
the mirror through the alignment scope attached
to the transmitter mount. Adjust the pan and tilt of
the transmitter housing until the cross hairs of the
transmitter alignment scope are centered on the
mirror.
3. Adjust the pan and tilt of the receiver housing until
the cross hairs of the receiver alignment scope
are centered on the mirror.
4. One person should remain at the mirror to adjust
the pan and tilt. The second person should stand
about six feet from the mirror and find the reflection of the transmitter lamp in the mirror. The first
person should adjust the pan and tilt of the mirror
so that the second person is moved into the direct
line between the mirror and the receiver, keeping
the reflection of the transmitter lamp in sight.
Once on the direct line, the second person should
back away from the mirror toward the receiver,
keeping the reflection sighted. The first person
should adjust the pan and tilt of the mirror so that
the second person keeps the reflection in sight as
he gradually backs up to the center of the receiver.
5. Remove the receiver window assembly by rotating it counterclockwise. Avoid touching the window with bare hands. Move the window assembly to a safe place, being careful not to scratch
the window.
6. Set the MODE selector switch on the front panel
to the “align” position.
7. Using the test jacks on the front panel, connect a
digital voltmeter (with a resolution of at least 1 millivolt dc) between the NUMERATOR and Signal
Ground (SIG GND) and note the signal strength.
8. Make small adjustments in the receiver pan and
tilt to maximize the amplitude of the voltage at the
receiver.
9. Make small adjustments in the transmitter pan
and tilt to maximize the amplitude of the voltage
at the receiver.
10. Make small adjustments in the mirror pan and tilt
to maximize the voltage at the receiver.
11. Replace the receiver window assembly and read
the output at the junction box. The output
obtained should be between 0.3 and 0.5 vdc.
NOTE
For any given path length, the signal strength will
decrease as the angle formed by the transmitter/mirror/receiver configuration increases. If the
output obtained is not within the specified limits
after following all steps of the “Optical
Alignment/Signal Strength” procedure. The
preamplifier gain must be adjusted as described
in Step 12. If the output is correct, proceed to
Step 13.
12. To adjust the preamplifier gain, follow the
“Accessing Internal Components” procedure (see
“Maintenance” Section) and locate the preamplifier p.c. board within the heat sink fins. The
preamplifier gain adjustment potentiometer is
located on the preamplifier p.c. board and can be
reached by inserting a screwdriver between the
23 95-8400
fins from the bottom of the heat sink (as viewed
when the cover is open, but attached to housing
by its hinges).
If the output voltage is less than the specified
minimum, turn the preamplifier gain potentiometer
clockwise. If the output voltage is greater than
0.5 vdc, turn the preamplifier gain potentiometer
counterclockwise.
13. Once optimum alignment has been obtained,
carefully adjust the locking knob assembly on the
back of all three mounts so that the swivel foot on
the end of the shaft just makes contact with the
back of the front plate. DO NOT overtighten the
locking knob assembly.
14. View the mirror through the receiver alignment
scope to verify that the cross hairs are centered
on the mirror. If the cross hairs are not centered,
and optimum alignment is verified, adjust the
cross hairs to center on the mirror using the
adjustment knobs provided on the scope.
Replace the protective end caps on the alignment
scope.
15. Repeat Step 14 for the transmitter alignment
scope.
NOTE
Optimum alignment must be accurately maintained to ensure proper operation of the instrument. Careful adjustment of the alignment scope
cross hairs will enable verification of alignment
accuracy.
16. Recheck that the output has not been affected by
Steps 13 through 15.
17. Remove the receiver window assembly and return
the MODE selector switch on the front panel to
the “operate” position. Replace the window
assembly.
24
115 VA C – LINE
115 VA C – NEUTRAL
POWER GROUND
CHANNEL 1 OUTPUT
SIGNAL GROUND
CHANNEL 3 OUTPUT
STATUS ALARM – COMMON
STATUS ALARM – N.C.
HC ALARM – N.C.
HC ALARM – COMMON
L
N
1
2
3
4
5
6
7
Figure A1—Terminal Block Wiring
25 95-8400
10
8
6
4
2
0
02468101214161820
OUTPUT CURRENT (MILLIAMPERES DC)
INPUT
VOLTAGE
(VDC)
A1394
Figure A2—Voltage - Current Transfer Curve of the 4 to 20 Milliampere Converter
26
Figure A3
Figure A4
27 95-8400
Figure A5
Figure A6
28
Figure A7
Figure A8
29 95-8400
Figure A9
Figure A10
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