AST ELECTRO REV-J JULY 15 2004.pub
Critical Environment Technologies
AST SERIES ANALOG TRANSMITTERS with
ELECTROCHEMICAL Carbon Monoxide SENSOR
General
Purpose
PVC
Water
/
Dust
Tight, Corrosion
R e s i s t a n t
Polycarbonate
INSTALLATION & INSTRUCTION MANUAL
For the “REV-J” transmitter board only - JULY 15, 2004
Unit 145, 7391 Vantage Way
Delta, BC Canada V4G 1M3
Phone: 604-940-8741 Fax: 604-940-8745 www.critical-environment.com
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2
TABLE OF CONTENTS
SECTION
DESCRIPTION
PAGE
1.0
General Description...............................................................4
1.1
Transmitter Specifications .....................................................4 - 5
1.2
Sensor Specifications ............................................................5
2.0
General Purpose PVC Enclosure Dimensions ......................6
2.1
General Purpose PVC Enclosure Interior Layout ..................7
2.2
Water / Dust Tight Enclosure Dimensions.............................8
2.3
Water / Dust Tight Enclosure Interior Layout ........................9
3.0
Installation Instructions ..........................................................10
4.0
Wiring Hook-Up Instructions..................................................10
4.1
Wiring Hook-Up Photo...........................................................11
5.0
Details of Operation...............................................................12
6.0
Maintenance Instructions ......................................................12
6.1
Calibration Procedure............................................................13 - 14
6.2
Local Digital Display Option ..................................................14
6.3
Calibration Set-Up Drawing / Photo ......................................15
6.3
Potentiometer & test point locations ......................................15
6.4
Sensor Replacement Instructions .........................................16
7.0
Parts Listing...........................................................................16
8.0
Accessories ...........................................................................16 - 18
9.0
Warranty ................................................................................18
Note-1: Due to ongoing development and testing, the manufacturer reserves the right to
change specifications and instructions without prior notice. Information contained in this
manual is considered accurate based on testing data available at the time of publication.
No warranty is expressed or implied regarding the accuracy of this data. The manufacturer
does not accept liability for damages resulting from the use of this product. This product is
only to be used for purposes stated herein.
Note-2: Read and understand this operation manual prior to using this gas detector. This
equipment should be inspected and maintained by a qualified and trained technician.
Regular calibration maintenance (6 month frequency) is required to maintain best accuracy
and reliability of the sensor / transmitter and to provide indication of an expired
electrochemical sensor element.
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1.0 GENERAL DESCRIPTION
The AST-MCO Rev-J are remote mount analog transmitting gas detectors with integral,
electrochemical Carbon Monoxide sensor and either general purpose pvc or water /
dust tight, corrosion resistant polycarbonate enclosures with hinged, secured doors and
Lexan labels. This series of transmitters has been designed for commercial and light
industrial applications such as underground vehicle parking, pools, arenas,
maintenance shops, water and sewage treatment plants, etc. For use only in
environments that are not classified as explosive.
The AST-MCO Rev-J transmitters provide continuous monitoring with continuous
analog signal output, representing the quantitative presence of gases / vapours. The
industry standard 4 - 20 mA or 0 - 10 VDC signal is linear and can be “fed” directly into
a building management system, PLC, or any generic controller that will accept an
analog signal. The controlling device can then utilize the continuous analog signal to
provide a measured control output for exhaust fans, alarms, etc.
1.1 TRANSMITTER SPECIFICATIONS
Size:
General Purpose: 4.50”H x 6.13”W x 2.56” TH (114 mm x 156 mm x 65 mm).
Water/Dust Tight: 4.92”H x 4.92”W x 2.56” TH (125 mm x 125 mm x 65 mm).
Weight:
9 ounces (148 grams) both enclosures
Construction:
General Purpose: Very rugged, heavy wall pvc with hinged, secured door and Lexan
door label with viewing window for optional local LED digital display.
Water/Dust Tight: Very rugged, Polycarbonate (NEMA-4X - IP66 rated) with 3/32” thick
walls and hinged, secured door. Lexan door label with viewing window for optional local
LED digital display.
Power Requirements:
16 to 24 VAC or 20 to 30 VDC (unregulated or regulated)
Approximate current draw: 30 to 50 mA (maximum)
Output Signal:
Linear, analog 4 - 20 mA or 0 -10 VDC
Operating Temperature:
Range: -20 deg. C. to +50 deg. C.
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1.1 TRANSMITTER SPECIFICATIONS, CONT’D.....
Humidity:
10 to 95% (non-condensing)
Current Loop Resistance:
Maximum 1000 Ohms
Options:
a) Local display, LED, 3 1/2 digits (3/8” digits)
b) Local dry contact relay 2 amps @ 28 VDC S.P.D.T.
C) water/dust tight, corrosion resistant enclosure
D) Splash guard (for water tight enclosure option, only)
1.2 SENSOR SPECIFICATION
Carbon Monoxide: (Commercial HVAC) Model: AST-MCO
* Range: 0 - 200 ppm (HVAC CO) (other ranges available)
* Response Time: <30 seconds to 90% of signal response
* Operating Temp. Range: -20 deg. C. to +50 deg. C.
* Long Term Drift: <2% signal loss/ year typically
* Repeatability: 2% of signal
* Life Span: 5 years “plus” in air (under normal conditions)
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2.0 GENERAL PURPOSE PVC ENCLOSURE DIMENSIONS
6.4” (165 mm)
4.44” (113 mm)
DIGITAL PHOTO #1
OPTIONAL LED
DIGITAL DISPLAY
LEXAN LABEL
INTEGRAL CO
SENSOR
DOOR SECURING
SCREW
RUGGED, MOLDED
PVC ENCLOSURE
WITH MOLDED IN
HINGES
DIGITAL PHOTO #2
2.54” (65 mm)
SIDE ACCESS
CONDUIT ENTRY
PORTS
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2.1 GENERAL PURPOSE PVC ENCLOSURE INTERIO LAYOUT
CONDUIT ENTRY POINTS
DIGITAL PHOTO #3
ENCLOSURE DOOR SNAPS OFF SO
INSTALLER HANDLES ONLY EMPTY
BASE FOR INSTALLATION.
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2.2 WATER / DUST TIGHT ENCLOSURE DIMENSIONS
4.92” (125 mm)
4.92” (125 mm)
DIGITAL PHOTO #4
RUGGED, POLYCARBONATE WATER /
DUST TIGHT, CORROSION RESISTANT
ENCLOSURE WITH POLYCARBONATE
HINGES AND DOOR SCREWS
2.92” (75 mm)
DIGITAL PHOTO #5
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2.3 WATER / DUST TIGHT ENCLOSURE INTERIOR LAYOUT
MOUNTING HOLES INDICATED
MUST BE USED TO MAINTAIN
WATER TIGHT RATING OF
ENCLOSURE
DAMAGE TO CIRCUIT OR SENSOR
ARISING FROM IMPROPER
INSTALLATION OF THIS
ENCLOSIRE IS NOT COVERED
UNDER WARRANTY
THESE MOUNTING HOLES MUST
BE USED BECAUSE THEY ARE
OUTSIDE OF THE DOOR GASKET.
DIGITAL PHOTO #6
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3.0 INSTALLATION INSTRUCTIONS
General Purpose: Four 3/16” diameter mounting holes are located on the inside
of the enclosure.
Water/Dust Tight Four 3/16” diameter mounting holes are located on the inside edge of
the transmitter enclosure. They are accessed through the holes for the lid securing screws.
(See section 2.0 drawing). One conduit entry port can be found on the top edge of the
transmitter enclosure. If this enclosure is to be utilized in an atmosphere that truly
requires a water tight enclosure, be sure to use the appropriate liquid tight conduit
connector.
Sensor Mounting Height and Locations
Carbon Monoxide: CO is slightly lighter than air and so the transmitter should be installed
approximately 4’ to 6’ from the floor (Breathing Zone).
Note-1: Never install sensors in the direct path of moving air, such as exhaust
fans, make-up air fans, ducts (without duct aspirator attachment), etc. Sensors
should be installed in areas where air movement is poor and gases may have a
tendency to build and present danger to people.
4.0 WIRING HOOK-UP INSTRUCTIONS
For VAC powered installations, utilize 18 - 22 gauge, 4-conductor shielded cable. Connect
the two VAC power wires to the “24V” input terminals (top two terminal strip locations).
Connect the remaining two wires, designated negative and positive, to the “SIG -” and “SIG
+“ input terminals (terminal strips 3 & 4 from the top). Be sure to observe polarity labeling
when connecting these wires.
For VDC powered installations, utilize 18 - 22 gauge, 3-conductor shielded cable. Connect
the positive and negative wires to “24V” and “SIG-” input terminals (terminal strips 2 & 3
from the top). Connect the third wire to the “SIG.+” input terminal (terminal 4 from the top).
Be sure to observe polarity labeling when connecting these wires.
Note-1: For either VAC or VDC powered installations, be sure to observe
minimum and maximum voltage operation limitations, as indicated in section 1.1
“Transmitter Specifications”, under “Power Requirements” and section 4.0
“Wiring Hook-up Instructions”. Note: Maximum current loop resistance = 1000
ohms.
Note-2: For connecting the 0-10 VDC output signal versions, it is best to use
four wires. Two for VAC power to the transmitter and two for your voltage
output signal. Wire runs must be kept quite short to avoid line loss and
interference which will result in inaccurate signals.
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4.1 WIRING HOOK-UP DRAWING
TERMINAL
PLUGGED IN
24V
24VAC
24V
24VAC OR 24VDC
SIG-
SIGNAL NEGATIVE
SIG+
SIGNAL POSITIVE
N/O
RELAY– N/O
COM
RELAY– COM
N/C
RELAY– N/C
DIGITAL PHOTOS #7 AND #8
TERMINAL
UNPLUGGED
The wiring terminal unplugs for easier attachment of wires.
The photos above indicate the standard wiring sequence. The photo on the left indicates
the wiring terminal attached or plugged in. The photo on the right indicates the wiring
terminal removed or unplugged.
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5.0 DETAILS OF OPERATION
When power has been applied to the transmitter, the electrochemical CO sensor output
signal to circuit will rise, possibly indicating gas alarm conditions on the building
management system or whatever controller the output signal is connected to. This condition
may last for several minutes to 20 minutes while the sensor stabilizes in the new
environment.
Once the sensor stabilizes, the transmitter output signal will automatically settle down to
normal operating state (non-gas alarm condition = 4.00 mA or 0 vdc), if no background gas
is present. The signal will represent the concentration of gas present in the environment, if
any. A green LED, visible through the door label window, will illuminate continuously, to
indicate that power has been properly connected. The transmitter circuit is protected by an
“automatic resetting” thermal fuse. In the event that the green LED does not illuminate,
check to ensure that the wiring is properly connected and measure the supply voltage input
to ensure there is indeed power applied to the transmitter circuit. If an improper
connection has caused the fuse to blow, it will reset itself. To achieve this,
disconnect the supply voltage wires for approximately 3 minutes (allowing the fuse
time to cool down and reset), then reconnect supply voltage wires correctly.
A red LED located on the middle bottom area of the circuit board, acts as a signal loop
“open loop” indicator. If it is illuminated, the 4-20 mA signal loop has not been connected
properly. If a proper connection has been made, the red LED will not illuminate.
Note: The open loop indicator works only with current output transmitter, not voltage
output transmitters.
A powered up transmitter in normal operating state (non gas environment) will have a linear
analog signal output of approximately “4.00 mA” or “0” VDC, which = “0” ppm gas. Once
gas has been detected, the transmitter signal will rise through the sensor detection range of
4-20 mA or 0-10 VDC. Eg. electrochemical CO sensor (standard range: 0 - 200 ppm): a
concentration of 25 ppm = 6.0 mA or 1.25 VDC. All signal output readings for
electrochemical sensors are accurate to the specifications listed on preceding pages.
Note: Some gases, vapours and other compounds may interfere with the sensors
causing gas alarm conditions because of cross-sensitivity. This potential problem
should be minimal (application dependent), because of the specificity of the sensors.
It is highly recommended that sensor / transmitters installed in new construction
areas be sealed with plastic bags immediately after installation to prevent
contamination or damage from construction materials and liquids.
Direct exposure to strong solvent vapours may contribute to deterioration of the
electrochemical sensor element.
6.0 MAINTENANCE INSTRUCTIONS
All transmitters should be inspected on-site after installation to ensure that they have been
installed and connected properly. All transmitters have been factory calibrated twice, prior to
shipping, but on-site gas tests serve to confirm accuracy of zero (null) and span settings, in
the event that they may have been tampered with. Regular maintenance is minimal and
consists of one to two times per year on-site gas calibration (application dependent). A
digital multi-meter will confirm the transmitter output signal response and will help to
indicate when a sensor element is ready to be replaced.
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6.1 CALIBRATION PROCEDURE
Important: Ensure that the transmitter has been powered up for at least 2 -4 hours prior to
calibration to ensure that the sensor has completely stabilized.
Equipment Required:
a) Precision digital multi-meter capable of displaying a VDC scale of “0.000”.
b) Small blade screwdriver (to adjust potentiometer)
c) Calibration kit with the proper cylinders of calibration gas
Note: Transmitter must be connected to system signal loop to see voltage readings at test
points.
Calibration Equations:
CALIBRATION GAS PPM
X 16 + 4 = mA SIGNAL EXPECTED
SENSOR SPAN RANGE PPM
CALIBRATION GAS PPM
X 10 = VDC SIGNAL EXPECTED
SENSOR SPAN RANGE PPM
Procedure:
Step-One: Connect leads from digital multi-meter (observe polarity) to test points “TP6+”
and “TP7-”. Set meter to VDC scale “.000”. Attach cylinder of “zero emissions air” to
regulator (flow rate 0.2 to 0.5 LPM). Moisten o”ring of adapter plug and gently push into
sensor shroud on enclosure door. Turn regulator fully on. Flow zero air for approximately
two minutes to allow sensor to stabilize. Observe meter reading. Signal displayed should
read approximately “.000”. If it does not, then carefully adjust “NULL” pot. to obtain this
reading. Reference photo on page 13.
Alternative for Step-1: If zero air is not available, install both zeroing plug caps for
calibration adapter and allow sensor to stabilize for approximately three to five minutes
before adjusting the “NULL” pot. Be sure to remove both zeroing plug caps before flowing
gas.
Note-1: If transmitter is fitted with local digital display, it will automatically zero along with
the transmitter circuit.
Step-Two: With zero emissions air still flowing, move meter leads to test points “TP-1+”
and “TP-2-”. These are the signal output test leads. Adjust the 4 mA potentiometer to
achieve “0.400” VDC.
Step-Three: Using one of the formulas indicated above, calculate what signal is to be
expected from the concentration of calibration gas being utilized. Attach cylinder of
calibration (span) gas and turn regulator fully on. Flow calibration gas for approximately two
to three minutes.
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6.1 CALIBRATION PROCEDURE, CONT’D.....
Observe meter reading. Note: 4-20 mA signal at test points “TP1” and “TP2” is across a
100 ohm resistor which coverts it to a voltage signal (4 - 20 mA = 0.400 to 2.00 VDC). The
expected mA reading calculated from the formula on the previous page should be divided
by ten, to arrive at the correct, expected voltage signal. Eg: an expected reading of “7.2
mA” will be displayed as “0.72 VDC”. If the reading displayed after approximately three
minutes of gas flow is not what you calculated, adjust the “SPAN” pot. to achieved the
desired reading.
Allow sensor approximately 10 minutes to recover, then recheck the null output at test
points “TP-6+” and “TP-7-”. Readjust to “0.000” VDC if necessary. Do not make this adjustment until the sensor has stabilized for at least 10 minutes. The null and span potentiometers do not interact with each other, so an additional span adjustment should not be required.
Shut off gas flow and remove regulator from cylinder for storage. Calibration procedure
is finished.
If the sensor / transmitter being calibrated is fitted with a local digital display, it
adjustment. It is factory set to display what the circuit indicates.
requires no
6.2 LOCAL DIGITAL DISPLAY OPTION
1. When a local LED digital display is ordered, a second circuit board is attached between
the main board and the door of the enclosure. The edge of the display board is visible along
the right side of the main board. No adjustments are required.
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6.3 CALIBRATION SET-UP DRAWING
FLOWING GAS
RESETTABLE
FUSE
DIGITAL PHOTO #9
DIGITAL
DISPLAY
BOARD
SPAN POT.
NULL POT.
NULL TEST
POINTS
TP-6 & TP-7
4 mA
SET POT.
RELAY OPTION,
IF SUPPLIED
WOULD BE
FOUND IN THIS
AREA
0-10 VDC COMMON
0-10VDC SIGNAL
OPEN LOOP
LED
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TP-2 (-) (4-20 mA)
TP-1 (+) (4-20 mA)
6.4 SENSOR REPLACEMENT INSTRUCTIONS
If the electrochemical sensor element of the transmitter must be replaced, please follow
these instructions. Very carefully remove the four screws and washers securing the circuit
board to the enclosure door. Carefully lift out the transmitter circuit board, handling only the
edges of the board. Grasp the electrochemical sensor by it’s edges and gently tug on it to
unplug it. Remove shorting bar / spring from new sensor. Plug in new replacement
sensor, being careful to maintain pin configuration. Remove the old sponge gasket and install the new gasket in the same position. Re-attach the transmitter circuit board and
replace the four securing screws and washers securely (do not over tighten nuts).
NOTE: Whenever replacing any sensor element, a complete calibration procedure is
required (see section 6.1 on pages 13 & 14).
7.0 PARTS LISTING
DESCRIPTION
PART NUMBER
PVC transmitter enclosure (general purpose)
AST-8700-EN1
Polycarbonate transmitter enclosure (water tight)
AST-8700-EN4
Transmitter circuit board
AST-7000-TCB
Sensor shroud (dark gray)
AST-8700-USS
Transmitter door securing nuts (polycarbonate)
Consult Factory
Calibration adapter plug (accessory)
AST-7000-CAP
Transmitter protective guard (accessory)
SCS-8000-RSG
Electrochemical sensor elements:
Carbon Monoxide - HVAC
SEC-7000-MCO
8.0 ACCESSORIES
Calibration Gases:
Zero Emissions Air (17 liter disposable cylinder)
(also available in 105 liter cylinders)
CG1-ZERO
Carbon Monoxide 100 ppm (17 liter disposable cylinder)
(also available in 105 liter cylinders)
CG1-CO-100
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NOTE: For all calibration span gases, contact Critical Environment Technologies Canada Inc. for desired type of gas, size of cylinder and appropriate cylinder regulator.
Reactive gases such as Chlorine, Ammonia and others have a considerably shorter
life span in cylinders than non-reactive gases. The type of gas usually determines the
type and sizes of cylinders available.
For ease of operation in the field, all gases can be flowed at 0.5 LPM. If regulators
with other flow rates are used, a slight difference in response may be noticed.
Store all cylinders of calibration
temperatures above freezing.
gas
with
regulators
removed
and
8.0 ACCESSORIES
DIGITAL PHOTO #10
Calibration kits, gases and metal protective guards
17
at
8.0 ACCESSORIES , CONT’D.....
METAL PROTECTIVE GUARD DRAWING
9.0 WARRANTY
All AST-MCO Rev-J series analog transmitters are warranted against defects in
materials and workmanship for a period of two years from the date of shipment from
Critical Environment Technologies Canada Inc. (CETCI), including the electrochemical
CO sensor element. Throughout the warranty period, we will repair or replace any
component that proves to be defective, in our opinion, as a result of “normal use”.
Critical Environment Technologies Canada Inc. is not liable for damage caused by
transmitters that have not been regularly maintained and calibrated as per our written
instructions, or auxiliary interfaced equipment, or consequential damage. All returned
goods must be shipped to Critical Environment Technologies Canada Inc. by prepaid
freight. If, in our opinion, the repaired or replaced component proves to be defective,
we will reimburse the customer for shipping costs based on the most economical
freight carrier rates at the time. Contact CETCI for an RMA (Returned Merchandise
Authorization) number before shipping any product back for service or evaluation.
Pro-rated electrochemical sensor warranty: The sensor will be replaced if it fails within 6
months. After six months, the warranty will be pro-rated at a rate of 1/24th for each month
beyond the sixth month to a maximum of 24 months. The warranty will be calculated as
follows: Cost of the sensor multiplied by the age of the sensor in months, minus six months
divided by 24. Example: Sensor is 8 months old and expires prematurely. The replacement
cost is $100.00 (example cost only). The non-warranty portion will be 100 X 8 - 6 / 24 =
33% of the cost of the new sensor.
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9.0 WARRANTY, CONT’D…..
Due to on-going product research and development, Critical Environment
Technologies Canada Inc. reserves the right to change specifications without notice.
The information contained herein is based on data considered accurate. However, no
warranty is expressed or implied regarding the accuracy of this data.
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