MSA ZGARD S User manual

Gas Sensors
Instruction Manual
UWARNING
THIS MANAUL MUST BE CAREFULLY READ BY ALL INDIVIDUALS WHO HAVE OR WILL HAVE
THE RESPONSIBILITY FOR INSTALLING, USING OR SERVICING THIS PRODUCT. Like any piece
of complex equipment, this product will perform as designed only if installed, used and serviced in
accordance with the manufacturer’s instructions. OTHERWISE, IT COULD FAIL TO PERFORM AS
DESIGNED AND PERSONS WHO RELY ON THIS PRODUCT FOR THEIR SAFETY COULD
SUSTAIN SEVERE PERSONAL INJURY OR DEATH.
The warranties made by Mine Safety Appliances Company with respect to these Products are voided if the
products are not installed, used and serviced in accordance with the instructions in this user guide. Please
protect yourself and others by following them. We encourage our customers to write or call regarding this
equipment prior to use or for any additional information relative to use or repair.
Instrument Division 1-800-MSA-INST or FAX [phone]
MSA International [phone] or FAX [phone]
In Canada 1-800-267-0672 or FAX [phone]
© Mine Safety Appliances Company 1996 - All Rights Reserved
MINE SAFETY APPLIANCES COMPANY
PITTSBURGH, PENNSYLVANIA 15230
REV1.2 April2005 10063481

MSA
Permanent Instrument Warranty
1. Warranty- Seller warrants that this product
will be free from mechanical defect or faulty
workmanship for a period of eighteen (18)
months from date of shipment or one (1) year
from installation, whichever occurs first,
provided it is maintained and used in
accordance with Seller’s instructions and/or
recommendations. This warranty does not
apply to expendable or consumable parts
whose normal life expectancy is less than one
(1) year such as, but not limited to, non-
rechargeable batteries, filament units, filter,
lamps, fuses etc. The Seller shall be released
from all obligations under this warranty in the
event repairs or modifications are made by
persons other than its own or authorized
service personnel or if the warranty claim
results from physical abuse or misuse of the
product. No agent, employee or representative
of the Seller has any authority to bind the
Seller to any affirmation, representation or
warranty concerning the product. Seller makes
no warranty concerning components or
accessories not manufactured by the Seller,
but will pass on to the Purchaser all warranties
of manufacturers of such components. THIS
WARRANTY IS IN LIEU OF ALL OTHER
WARRANTIES, EXPRESSED, IMPLIED OR
STATUTORY, AND IS STRICTLY LIMITED
TO THE TERMS HEREOF. SELLER
SPECIFICALLY DISCLAIMS ANY
WARRANTY OF MERCHANTABILITY OR OF
FITNESS FOR A PARTICULAR PURPOSE.
2. Exclusive Remedy- It is expressly agreed
that Purchaser’s sole and exclusive remedy for
breach of the above warranty, for any tortious
conduct of Seller, or for any other cause of
action, shall be the repair and/or replacement
at Seller’s option, of any equipment or parts
thereof, which after examination by Seller is
proven to be defective. Replacement
equipment and/or parts will be provided at no
cost to Purchaser, F.O.B. Seller’s Plant.
Failure of Seller to successfully repair any
nonconforming product shall not cause the
remedy established hereby to fail of its
essential purpose.
3. Exclusion of Consequential Damage-
Purchaser specifically understands and agrees
that under no circumstances will seller be liable
to purchaser for economic, special, incidental
or consequential damages or losses of any
kind whatsoever, including but not limited to,
loss of anticipated profits and any other loss
caused by reason of non operation of the
goods. This exclusion is applicable to claims
for breach of warranty, tortuous conduct or any
other cause of action against seller.

General Warnings
UWARNING
1. The ZGARD S & DS gas sensors
described in this manual must be
installed, operated, and maintained
in strict accordance with the labels,
cautions, warnings, instructions,
and within the limitations stated.
2. The ZGARD S & DS gas sensors
must not be installed in outdoor
areas or in locations where
explosive concentrations of
combustible gases or vapors might
occur in the atmosphere: Class 1,
Group A, B, C, and D areas as
defined by the NEC. Because the
gas sensors are not explosion-
proof, they must be located in non-
hazardous areas.
3. Do not paint the ZGARD S & DS
gas sensors.
4. The only absolute method to assure
the proper overall operation of a
gas detection instrument is to check
it with a known concentration of the
gas for which it has been calibrated.
Consequently, a calibration check
must be included as part of the
installation and as a routine
inspection of the system.
5. Use only genuine MSA replacement
parts when performing any
maintenance procedures provided
in this manual. Failure to do so may
seriously impair instrument
performance. Repair or alteration of
the ZGARD S & DS gas sensors,
beyond the scope of these
maintenance instructions or by
anyone other than authorized MSA
service personnel, could cause the
product to fail to perform as
designed, and persons who rely on
this product for their safety could
sustain serious personal injury or
death.
6. The ZGARD S & DS gas sensors
must be installed, located and
operated in accordance to all
applicable codes. These codes
include, but are not limited to, the
National Fire Prevention Code and
National Electric Code.
7. Do not exceed the relay contact
ratings listed in this manual.
Otherwise, the relay operation may
fail, which can result in personal
injury or death.
Failure to comply with the above warnings
can result in serious personal injury or
death.

Table of Contents
Section 1 General Information and Applications 1.0
Section 2 Installation Guidelines 2.0
Section 3 ZGARD S Sensors, Operating Specifications and Features 3.0
Installation and Set-up RS485 Sensor Address Binary Coded Setup, Output Test, Cut-Off Feature 3.1
Section 4 ZGARD S Carbon Monoxide Solid-State (SS) Sensor, 4-20mA Output, Sensor Calibration 4.0
RS485 Output, Solid-State (SS) Sensor Calibration 4.1
Section 5 ZGARD S & DS Carbon Monoxide Electrochemical (EC) Sensor, 4-20mA Output, Sensor Calibration 5.0
RS485 Output, Electrochemical (EC) Sensor Calibration 5.1
Section 6 ZGARD S & DS Nitrogen Dioxide Electrochemical (EC) Sensor, 4-20mA Output, Sensor Calibration 6.0
RS485 Output, Electrochemical (EC) Sensor Calibration 6.1
Section 7 ZGARD S Refrigerant Solid-State (SS) Sensor, 4-20mA Output, Sensor Calibration 7.0
RS485 Output, Solid-State (SS) Sensor Calibration 7.1
Section 8 ZGARD S Ammonia Solid-State (SS) Sensor, 4-20mA Output, Sensor Calibration 8.0
RS485 Output, Solid-State (SS) Sensor Calibration 8.1
Section 9 ZGARD S & DS Sensors Start-Up Procedure 9.0
Section 10 Parts List 10.0
Drawings
106890B CO (SS), 4-20mA Output Sensor Circuit Board Layout
106891B CO (SS), RS485 Output Sensor Circuit Board Layout
106892B CO/NO2 (EC), 4-20mA Output Sensor Circuit Board Layout
106893B CO/NO2 (EC), RS485 Output Sensor Circuit Board Layout
106949B Rx (SS), 4-20mA Output Sensor Circuit Board Layout
106950B Rx (SS), RS485 Output Sensor Circuit Board Layout
106951B Ammonia (SS), 4-20mA Output Sensor Circuit Board Layout
106952B Ammonia (SS), RS485 Output Sensor Circuit Board Layout
106894B (SS) Sensors Calibration Gas (Humidified) Setup Procedure
106895B ZGARD S, Installation Outline, 4-20mA Output Sensor
106896B ZGARD S, Installation Outline, RS485 Digital Sensor
106897B ZGARD S, Installation Outline, 4-20mA Output, Stand-Alone Sensor
106953B ZGARD DS, Installation Outline, 4-20mA Output Sensors
106954B ZGARD DS, Installation Outline, RS485 Output Sensors
106955B ZGARD DS, Installation Outline, 4-20mA Output, Stand-Alone Sensors

Section 1
ZGARD S & DS Gas Sensors
General Information and Applications
The ZGARD S Sensors are designed to detect the presence of Carbon Monoxide, Nitrogen Dioxide, Refrigerants or
Ammonia in air. The EC type employs electrochemical plug-in cells. The solid-state (SS) type employs Metal Oxide
Semiconductor (MOS) sensing technology. Each sensor generates a representative output signal proportional to the
calibrated operating range.
The ZGARD DS is a Dual Sensor in one enclosure and both sensors employ Electrochemical (EC) plug-in cells. The ZGARD
DS sensor is designed to detect the presence of Carbon Monoxide and Nitrogen Dioxide in air.
The ZGARD S & DS sensors are available with two output versions, a 4-20mA analogue output or an addressable RS485
digital signal. The ZGARD S & DS, RS485 version is specifically designed to operate with any MSA ZGARD C 485
Controllers, operating as a system. The ZGARD S & DS with 4-20mA output can be installed as a stand-alone sensor
typically integrated with common commercial equipment including PLC, DCS or Building Environmental Automation
Systems.
The table below provides the distinctive features of the ZGARD S & DS Sensors. This is a quick guide for
determining the operating features of each sensor.
ZGARD S & DS
SENSORS
CARBON
MONOXIDE (SS)
CARBON
MONOXIDE (EC)
NITROGEN
DIOXIDE (EC)
REFRIGERANTS
(SS) AMMONIA (SS)
Principal of
Operation
MOS, Metal Oxide
Semiconductor Electrochemical Electrochemical Metal Oxide
Semiconductor
Metal Oxide
Semiconductor
Operating Range
0-100ppm
OR
0-200ppm
0-100ppm
OR
0-200ppm
0-10ppm 0-1,000ppm 0-500ppm
On-Board Test
50 & 100% Full
Scale Output Test
jumper
0 & 100% Full Scale
Output Test jumper
0 & 100% Full Scale
Output Test jumper
50 & 100% 0Full
Scale Output Test
jumper
50 & 100% Full
Scale Output Test
jumper
Output
4-20mA
OR
RS485 Network
4-20mA
OR
RS485 Network
4-20mA
OR
RS485 Network
4-20mA
OR
RS485 Network
4-20mA
OR
RS485 Network
Calibration Zero and Span
Potentiometers
Zero and Span
Potentiometers
Zero and Span
Potentiometers
Zero and Span
Potentiometers
Zero and Span
Potentiometers
Cut-Off Feature 17ppm NONE NONE 65ppm 50ppm
Periodic inspections and calibration: This unit requires calibration. The calibration frequency will be a function of the operating conditions,
including operating under extreme temperatures, exposure to contaminants or gas concentrations greater than the lower explosive limits. A
calibration inspection must be included as part of a routine maintenance to ensure proper operation of the gas detection unit. If unit span or
zero cannot be adjusted, the sensor may be approaching its end-of-life or has been contaminated and must be replaced.
The performance of any ZGARD S & DS Sensor is dependent on the appropriate and strategic placement within a guarded
area. The remote gas sensors should be strategically placed closest to the areas where the target gases or vapors might
occur in the atmosphere. Follow the recommended guidelines listed below.
Determination of number of sensors: The number of transmitters required is determined by a unit’s operational radius of
surveillance. Using table below, the number of units required can be easily evaluated.
Gas Detected Radius of Surveillance Guarded Area
CO Carbon Monoxide, NO2 Nitrogen Dioxide 50 feet (15 meters) 7,854 square feet (707 square meters)
Refrigerants, Ammonia 23 feet (7 meters) 1,662 square feet (154 square meters)
Surface-mount installation: Installation of the sensor simply requires the physical mounting of the enclosure and
connection of the power and output lines.
Target Gas Relative Density (air = 1) Recommended Height
CO Carbon Monoxide 0.968 3 - 5 feet (1 - 1.5 m ) from floor
* NO2 Nitrogen Dioxide 1.58 (cold) 1- 3 feet (30 cm to 1 m) from ceiling
R11 Refrigerant 5.04 1 foot (30 cm) from floor
R12 Refrigerant 4.20 1 foot (30 cm) from floor
R22 Refrigerant 3.11 1 foot (30 cm) from floor
R134a Refrigerant 3.52 1 foot (30 cm) from floor
NH3 Ammonia 0.59 1 foot (30 cm) from ceiling
*May differ in certain applications. Hot NO2 from exhaust systems is lighter than ambient air.
1.0

Section 2
ZGARD S & DS Sensors
Installation Guidelines
Mounting:
•Do not mount the sensor to structures subject to vibration and shock, such as piping and piping
supports.
•Do not locate the sensor near excessive heat source or in wet and damp locations.
•For proper cooling, allow at least five inches of clearance around all surfaces except for the mounting
surface. Also consider mounting the sensor so it can be easily accessed for service and routine testing.
•The sensor has four mounting lugs; securely mount the instrument to a wall or support using
appropriate hardware.
Wiring Connections:
Before putting a ZGARD S & DS Sensor into operation, determine the elevation and the number of gas sensors
according to the required application. Also refer to the ZGARD S & DS sensor(s) Installation Outline drawings
located in the back of this manual, which provides important information regarding;
•Operating power.
•Required conductors and wire size.
•4-20mA and RS485 Network wiring connection.
UC
CA AU UT TI IO ON N
1. When wiring the sensor, disconnect the main power to prevent bodily harm.
2. Do not use the sensor power when connecting any external devices.
3. Use shielded cable for wiring installation. Do not install low voltage signal cable in the same conduit as
the other devices such as sensors operating power and or relay wiring.
4. Make sure that each sensor is given a unique address (Jumper selected), or the associated MSA
ZGARD C series controller may not be able to communicate appropriately.
5. When connecting the remote sensors, make sure that all wiring is correct for the power and signal
leads. Ensure the RS485 bus wiring is not interchanged, or permanent damage to the sensor may
result.
6. Perform all wiring and conduit installation in accordance to the National Electrical Code.
Failure to follow the above cautions can result in injury or property damage.
2.0

Section 3
ZGARD S & DS Sensors
General Information
OPERATING SPECIFICATIONS
Detection Range CO - Carbon Monoxide, 0-100 or 0-200ppm
Principal of Operation SS, Semiconductor OR EC, Electrochemical
Detection Range NO2 - Nitrogen Dioxide, 0-10ppm
Principal of Operation EC, Electrochemical
Detection Range R11, R12,R22 or R134a - Refrigerants, 0-1,000ppm
Principal of Operation SS, Semiconductor
Detection Range NH3 - Ammonia, 0-500ppm
Principal of Operation SS, Semiconductor
4-20mA Output Sensors
Operating Power 24Vdc, 100mA used with MSA ZGARD C Series Controllers
Connection 3-wire point-to-point connection
RS485 Digital Output Sensors
Operating Power 24Vdc, 100mA used with MSA ZGARD C Series Controllers
Connection RS485, 4-wire network connection
Digital Addressing Network Address jumpers, 1 to 127
4-20mA, Stand Alone Sensors
Operating Power 24Vdc, 100mA used with commercial DCS and PLC devices
24Vac, 100mA used with commercial DCS and PLC devices
Connection 3-wire point-to-point connection
Status LED Indicator Sensor OK
Temperature Operating: 0° to 40°C (32° to 104°F): Storage: -10° to 50°C (14° to 122°F)
Accuracy Solid-State (SS) Sensors +/- 5%, Full Scale (FS)
Electrochemical (EC) Sensors +/- 2%, Full Scale (FS)
Humidity 0 to 95% RH
ZGARD S Enclosure Standard, Plastic double-gang connection box with metal front cover
(Optional) NEMA 4X Fiberglass design OR Metal housing and cover
Dimensions 5.5” H (140 mm) x 5.5" W (140 mm) x 2.2" D (56 mm)
Weight 0.45kg (1.00 lbs.)
ZGARD DS Enclosure Standard, NEMA 4X Fiberglass
Dimensions 7.0” H (178 mm) x 10.5" W (267 mm) x 4.5" D (114 mm)
Weight 1.1kg (2.45 lbs.)
Certification ENTELA (to CSA Standards)
Sensor Outputs: The ZGARD S & DS Sensors provide
two sensor output options, a 4-20mA analogue output or
a RS485 digital signal. The ZGARD S & DS, RS485
sensor includes an identifiable digital signature
recognized by any MSA ZGARD C Series Controllers.
Sensing Technology: Toxic gasses are detected by way
of electrochemical cells, for targeting the gas of interest
and resolution. Moreover, second generations of semi-
conductor detectors offer a highly effective solution for a
variety of different applications.
LED Status: The Sensor OK LED is OFF for 30 seconds
upon power-up and will turn ON indicating that the device
is operating properly.
Onboard Communication Test: The ZGARD S (SS)
sensors provide a means of driving the output to 50% or
100% full-scale. The ZGARD S & DS (EC) sensors
provide a means of driving the output to 0% or 100% full-
scale. When the onboard test jumpers are inserted, the
sensor generates the selected output signal. This feature
is useful for testing remote devices, which may be
connected to the sensor output.
Enclosures: The standard ZGARD S sensor is housed in
a surface mount tamper resistant plastic enclosure. There
are two additional enclosure options, Metal housing and
cover plate or Fiberglass NEMA 4X housing. The
standard ZGARD DS sensor is housed in a Fiberglass
NEMA 4X housing.
Cut-Off Feature: The solid-state (SS) versions provide a
cut-off feature to eliminate possible high background
interferant's. This function is factory set to enable and is
also jumper selectable.
3.0

Section 3
ZGARD S & DS Sensors
Installation and Setup
On the main circuit of every ZGARD S & DS
Sensor is a set of RS485 Selection Jumpers
setting each sensor binary address code. The
H2 jumpers are located on the ZGARD S & DS
(SS) sensor boards and the H1 jumpers are
located on all ZGARD S & DS (EC) sensor
boards. Refer to the associated sensor
Installation Outline Drawing for further
details.
Table of the RS485 Sensor Address Codes
RS485 Digital Address Binary Code
Setup: The ZGARD S & DS Sensors with
RS485 digital output are recognized by MSA
ZGARD C controller. Each sensor must be
given a unique address code or it will not be
able to communicate correctly. The binary
address code is set by arranging the user
selection jumpers shown on H2-1, H2-2, H2-
3, H2-4, H2-5, H2-6 and H2-7 jumpers
located on the ZGARD S (SS) sensor
boards. The H1-1, H1-2, H1-3, H1-4, H1-5,
H1-6 and H1-7 jumpers are located on all
ZGARD S & DS (EC) sensor boards. Refer
to the associated sensor Installation
Outline Drawing for further details.
Connect a 4-conductor serial bus electrical
cable between the devices. The connection
terminal labeled Data 1 and Data 2 are for
communication while the +24Vdc and COM
are for power, supplied by the ZGARD C
Series controller. Make sure that all wiring is
correct and the four connecting leads of the
RS485 bus are not interchanged or
permanent damage to the sensor may result.
Refer to the associated ZGARD C Series
controller, Installation Outline drawing for
further details.
3.1
H2 (H1) RS485 ADDRESS 1 – 127
1 1 (SET BY BINARY)
2 2
3 4
4 8
5 16
6 32
7 64
Binary 1 2 4 8 16 32 64
Address H2-1
(H1-1)
H2-2
(H1-2)
H2-3
(H1-3)
H2-4
(H1-4)
H2-5
(H1-5)
H2-6
(H1-6)
H2-7
(H1-7)
1 IN OUT OUT OUT OUT OUT OUT
2 OUT IN OUT OUT OUT OUT OUT
3 IN IN OUT OUT OUT OUT OUT
4 OUT OUT IN OUT OUT OUT OUT
5 IN OUT IN OUT OUT OUT OUT
6 OUT IN IN OUT OUT OUT OUT
7 IN IN IN OUT OUT OUT OUT
8 OUT OUT OUT IN OUT OUT OUT
9 IN OUT OUT IN OUT OUT OUT
10 OUT IN OUT IN OUT OUT OUT
11 IN IN OUT IN OUT OUT OUT
12 OUT OUT IN IN OUT OUT OUT
13 IN OUT IN IN OUT OUT OUT
14 OUT IN IN IN OUT OUT OUT
15 IN IN IN IN OUT OUT OUT
16 OUT OUT OUT OUT IN OUT OUT
17 IN OUT OUT OUT IN OUT OUT
18 OUT IN OUT OUT IN OUT OUT
19 IN IN OUT OUT IN OUT OUT
20 OUT OUT IN OUT IN OUT OUT
21 IN OUT IN OUT IN OUT OUT
22 OUT IN IN OUT IN OUT OUT
23 IN IN IN OUT IN OUT OUT
24 OUT OUT OUT IN IN OUT OUT
25 IN OUT OUT IN IN OUT OUT
26 OUT IN OUT IN IN OUT OUT
27 IN IN OUT IN IN OUT OUT
28 OUT OUT IN IN IN OUT OUT
29 IN OUT IN IN IN OUT OUT
30 OUT IN IN IN IN OUT OUT
31 IN IN IN IN IN OUT OUT
32 OUT OUT OUT OUT OUT IN OUT
33 IN OUT OUT OUT OUT IN OUT
34 OUT IN OUT OUT OUT IN OUT
35 IN IN OUT OUT OUT IN OUT
36 OUT OUT IN OUT OUT IN OUT
37 IN OUT IN OUT OUT IN OUT
38 OUT IN IN OUT OUT IN OUT
39 IN IN IN OUT OUT IN OUT
40 OUT OUT OUT IN OUT IN OUT
41 IN OUT OUT IN OUT IN OUT
42 OUT IN OUT IN OUT IN OUT
43 IN IN OUT IN OUT IN OUT
44 OUT OUT IN IN OUT IN OUT
45 IN OUT IN IN OUT IN OUT
46 OUT IN IN IN OUT IN OUT
47 IN IN IN IN OUT IN OUT
48 OUT OUT OUT OUT IN IN OUT

Section 3
ZGARD S & DS Sensors
Installation and Setup
Solid-State (SS) Sensors, Output Test: Each
ZGARD Sensor provides a means of driving
the output to 50% or 100% full-scale.
Respectively, when the onboard test jumpers
are inserted the sensor generates the selected
output signal. This feature is useful for testing
remote devices, which may be connected to
the sensor output. Refer to the associated
sensor Installation Outline Drawing for
further details.
Solid-State (SS) Sensors, Cut-Off Feature:
Each ZGARD Sensor provides a cut-off option
to eliminate possible high background
interference of any unsuspected environmental
or other airborne compounds. This function is
jumper selectable. This function is factory set to
enable and is also jumper selectable.
Electrochemical (EC) 4-20mA Output
Sensors, 0% Output Test: Each ZGARD
Sensor provides a means of driving the output
to 0% full-scale. Respectively, when the
onboard test jumper is inserted the sensor generates the selected output signal. This feature is useful for testing remote
devices, which may be connected to the sensor output. Refer to the associated sensor Installation Outline Drawing for
further details.
Electrochemical (EC) 4-20mA Output
Sensors, 100% Output Test: Each ZGARD
Sensor provides a means of driving the output
to 100% full-scale. Respectively, when the
onboard test jumper is inserted the sensor generates the selected output signal. This feature is useful for testing remote
devices, which may be connected to the sensor output. Refer to the associated sensor Installation Outline Drawing for
further details.
Electrochemical (EC) RS485 Output
Sensors, 0% Output Test: Each ZGARD
Sensor provides a means of driving the output
to 0% full-scale. Respectively, when the
onboard test jumper is inserted the sensor generates the selected output signal. This feature is useful for testing remote
devices, which may be connected to the sensor output. Refer to the associated sensor Installation Outline Drawing for
further details.
Electrochemical (EC) RS485 Output
Sensors, 100% Output Test: Each ZGARD
Sensor provides a means of driving the output
to 100% full-scale. Respectively, when the
onboard test jumper is inserted the sensor generates the selected output signal. This feature is useful for testing remote
devices, which may be connected to the sensor output. Refer to the associated sensor Installation Outline Drawing for
further details.
3.2
H1
1 TEST FULL SCALE (100% OUTPUT)
2 TEST HALF SCALE (50% OUTPUT)
3
4 CUT-OFF (IN/ OUT)
5
6
7
8
H1
1 TEST FULL SCALE (100% OUTPUT)
2 TEST HALF SCALE (50% OUTPUT)
3
4 CUT-OFF (IN/ OUT)
5 17ppm for Carbon Monoxide Sensors
6 65ppm for Refrigerant Sensors
7 50ppm for Ammonia Sensors
8
H1
1 H1-ZS ZERO SCALE TEST (0% OUTPUT)
2 H1-FS FULL SCALE (100% OUTPUT)
H1
1 H1-ZS ZERO SCALE TEST (0% OUTPUT)
2 H1-FS FULL SCALE (100% OUTPUT)
H1
8 H1-ZS ZERO SCALE TEST (0% OUTPUT)
9 H1-FS FULL SCALE (100% OUTPUT)
H1
8 H1-ZS ZERO SCALE TEST (0% OUTPUT)
9 H1-FS FULL SCALE (100% OUTPUT)

Section 4
ZGARD S CO (SS) 4-20mA Output Sensor
Calibration
Calibration Procedure, Solid-State (SS) 4-20mA Output Carbon Monoxide Sensor: Perform calibration checks regularly
as part of a routine inspection and maintenance procedure. Use calibration gases of known and certified concentrations.
Check the expiry date on the gas cylinders. The ZGARD S sensor is factory calibrated for 100 or 200ppm Carbon Monoxide,
which represents 0 to 100% full scale. The 4-20mA output current between the connection terminals O/P and COM labeled
4-20mA output represents 0 to 100 % full-scale.
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The calibration procedure must be completed after the replacement of sensing cells.
Calibration Equipment
Flow controller 0.25 litres/minute and tubing
Purified air as zero gas and 60ppm CO in air span gas
Magnetic Strips
Electronic Multi-meter
Container of Distilled water with inlet and outlet tubing, required for humidifying the calibration gas. REFER: to Drawing
106894B.
Calibration Procedure
1. Disconnect the sensor output from the associated monitoring device. Using a multi-meter, insert test probes into the
connection terminals labelled O/P & COM.
2. Insert Jumper H1-4 to disable the sensor cut-off feature.
3. Place the magnetic strips on the top and bottom of the sensor cover plate, ensure the vent holes are fully covered.
UW
WA AR RN NI IN NG G
Remove the magnetic strips after the calibration has been completed. Otherwise it could fail to perform as designed and
persons who rely on this product for their safety could sustain severe personal injury or death.
ZERO Calibration
4. Join a 0.25 l/m., flow controller onto a ZERO gas cylinder. Insert a calibration adapter into thread port provided on the
protective cover located on the front plate.
5. Connect the ¼” Tygon tubing between the inlet of the gas humidification assembly and the calibration cylinder flow
controller outlet port.
6. Connect the outlet tubing of the gas humidification assembly to the sensor calibration adapter.
7. Turn ON the flow controller valve and allow the ZERO grade air to quench the sensor for at least 15 minutes.
8. Adjust the ZERO potentiometer until the current reading is equal to 4mA.
9. Turn OFF the valve and remove the flow controller from the Zero gas cylinder.
SPAN Calibration
10. Join the flow controller onto a SPAN gas cylinder. The SPAN gas should be at least 50% of the sensor’s operating range.
11. Turn ON the flow controller valve and allow the SPAN gas to quench the sensor for at least 15 minutes.
12. Adjust the SPAN potentiometer until the current reading is equal to the calculated value representing the gas
concentration. SEE: The equation below.
13. Turn OFF the valve and remove the flow controller from the SPAN gas cylinder.
14. Remove the test hose from the calibration adapter.
15. Remove the multi-meter test probes from terminals labelled O/P and COM.
16. Reconnect the sensor output to the associated monitoring device.
17. Remove Jumper H1-4 to enable the sensor cut-off feature.
Example: The SPAN gas concentration is 60ppm Carbon Monoxide in air.
4 - 20mA is 0-100% F.S., the current that is generated is 16 + 4 = 20mA.
60ppm = ((Span Gas Value x 16) / Full Scale)) + 4
= ((60 x 16) / 100)) + 4 = 13.6mA
4.0