Dwyer Instruments GSTC Series Supplement

The Series GSTC Carbon Monoxide/Nitrogen Dioxide Gas Transmitter
monitors the gas concentration in underground parking garages and loading docks.
The carbon monoxide transmitter is used to measure the exhaust of gasoline
engines, while the nitrogen dioxide transmitter is used for diesel engines. The
Series GSTC is compatible with either BACnet or MODBUS®communication
protocol, allowing the transmitter to be used with almost any building management
controller. The GSTC output is communicated over an RS-485 wire via BACnet or
MODBUS® communication protocol. To maximize the accuracy of the Series GSTC,
the sensor can be field-calibrated using the A-449 remote LCD display. When the
sensor reaches the end of its life, the display will indicate that the sensor needs to
be replaced.
BACnet and MODBUS®communication protocol recommend limiting the number of
nodes in any segment to 32. Therefore, the transceiver may be rated at one unit
load. Fractional loads are also acceptable. The Series GSTC accounts as an
eighth of a load on the MSTP network.
INSTALLATION
• The transmitter should be mounted at normal breathing height, approximately 5
to 6 ft above the floor.
• The unit may be mounted in the horizontal or vertical position. It should be
mounted in an area that is shielded from direct contact with the elements or direct
sunlight.
• Mount in an area that will prevent the sensor from having any direct contact with
water.
• The unit should be placed in an area that will give an average of the air quality.
Do not place the unit so it will receive direct engine exhaust. Prolonged exposure
to direct engine exhaust may damage the sensor.
Series GSTC Carbon Monoxide/Nitrogen Dioxide Gas Transmitter
Specifications - Installation and Operating Instructions
Bulletin AQ-GSTC
DWYE INST UMENTS, INC. Phone: [phone] www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A. Fax: [phone] e-mail: [email protected]
SPECIFICATIONS
Sensor: Field replaceable
electrochemical, 4 years typical
lifespan.
ange: CO: 0 to 500 PPM, NO2: 10
PPM.
Output Drift: <5% per year in air.
Coverage Area: 5000 to 7500 sq ft
typical.
Accuracy: CO: 2% FS, NO2: 3% FS,
at the time of calibration.
esolution: CO: 1 PPM; NO2: 0.1
PPM.
Temperature Limits: -4 to 122°F (-20
to 50°C).
Storage Temperature: For best
sensor life, 32 to 68°F (0 to 20°C).
Humidity Limits: 15 to 90% R
constant; 0 to 99% R intermittent.
esponse Time: <45 s to 90% CO,
<25 s to 90% NO2.
Span and Zero Adjustment: Via
pushbutton, using optional A-449
display. Zero only via BACnet or
MODBUS®communication protocol.
Housing: UV resistant glass filled
polycarbonate.
Output Signals: BACnet MS/TP or
MODBUS®RTU (switch selectable)
communication protocol.
Power equirements: 10 to 36 VDC
or isolated 21.6 to 33 VAC.
Electrical Connection: Removable
terminal block, knock outs for conduit
fitting.
Calibration: Via pushbuttons using A-
449 auxiliary display. Span gas
concentration is field selectable.
Enclosure ating: IP64.
Weight: 1 lb (0.45 kg).
Agency Approvals: CE.
Disconnect power supply before installation to prevent electrical
shock and equipment damage. Make sure all connections are in
accordance with the job wiring diagram and in accordance with national and local
electrical codes. Use copper conductors only.
WA NING
Use electrostatic discharge precautions (e.g., use of wrist
straps) during installation and wiring to prevent equipment
damage.
Avoid locations where severe shock or vibration, excessive
moisture, or corrosive fumes are present.
Do not exceed ratings of this device, permanent damage not
covered by warranty may result.
These are general guidelines. Local laws or ordinances will take
precedence.
NOTICE
NOTICE
NOTICE
NOTICE
3-45/64
[94.06]
3-1/8
[107.95]
2-15/64
[56.75]
4-17/32
[115.09]
5-7/64
[129.78] 3-59/64
[100]
2-15/64
[57]
2-55/64
[73]
3-23/64
[85]
Wall Mount Duct MountWall Mount
Without LCD
Duct MountWall Mount
With LCD
Figure 1 shows the location of the wiring terminal, 8 position DIP Switch SW1, used
for configuring the RS-485 address, the 4 position DIP Switch SW2, used for
configuring hardware and software options, sensor, span and zero adjustments,
and status LEDs.
The device provides three LEDs to indicate status and activity. The LEDs are
located to the right of DIP Switch SW1. The yellow LED indicates that the unit is
sending a BACnet or MODBUS®communication protocol. The green LED indicates
the unit is receiving a BACnet or MODBUS®communication protocol addressed to
this specific device. The red LED will flash once periodically if the BACnet or
MODBUS® communication protocol address is set incorrectly or the red LED will
flash twice periodically if the auto serial configuration is in progress.
Sensor
Span
Zero
Status
LEDs
Wiring
Terminal
DIP Switch
SW1
DIP Switch
SW2
Figure 1
The electrochemical sensors should be stored in an
environment with a minimum humidity level of 20% R . If the
sensor dries out, replacements will not be covered under warranty, but they can be
revived by allowing them to stabilize in an environment above 40% R for 10 days.
Once revived, they need to be recalibrated before use.
NOTICE

Figure 3 shows how to connect the GSTC in a network containing a common
power supply. Use a cable containing two twisted pairs. One pair is to be used for
the power and common. The other pair is to be used for A(-) and B(+). Attach the
shields together with a wire nut. This configuration is not suitable for AC supplies.
Use a DC supply only. Care should be taken that there are not too many devices
powered from the same supply as voltage drops will occur in the wiring. If you have
many devices, or have long cable runs, the local supply configuration, shown in
Figure 4, may be a better choice.
Figure 4 shows how to connect the GSTC in a network containing individual local
supplies. Use a cable containing a single conductor and a twisted pair. The single
conductor is to be used for common, and the pair is to be used for A(-) and B(+).
Attach the shields together with a wire nut. Both AC and DC supplies are suitable
for this configuration.
All devices in the network should be daisy-chained. Star connections and T
connections are not permitted.
The A(-) and B(+) lines must be terminated at both ends with a 120 ohm resistor.
If the GSTC is an end device it has an on-board resistor that may be used. See
Table 1 to enable it.
The network must be biased properly. If needed, there are bias resistors on-board
the GSTC. No more than two sets of bias resistors should be enabled in the
network. See Table 1 to enable them.
TO NEXT
DEVICE
B(+)
A(-)
PWR
COM
TO PREVIOUS
DEVICE
B(+)
A(-)
PWR
COM
ATTACH SHIELDS
TOGETHER W/WIRE NUT
PWRCOM A(-) B(+)
1234
Figure 3 - Common Power Supply
B(+)
A(-)
B(+)
A(-)
COM
-+
COM
TO PREVIOUS
DEVICE
TO NEXT
DEVICE
ATTACH SHIELDS
TOGETHER W/WIRE NUT
PWRCOM A(-) B(+)
1234
Figure 4 - Local Power Supply
Figure 2
Wall Mounting
1. Remove the cover plugs from the face of the unit and the top cover.
2. Disconnect the display cable from the USB connector on the main circuit board
(if present).
3. Remove the desired conduit fitting knock out and install conduit fitting (not
provided).
4. Position the transmitter where it is to be mounted and mark the mounting holes
in each corner of the housing.
5. Drill or punch out marked locations.
6. Place the transmitter box over mounting holes on wall and align. Install wall
mount screws (not provided) in mounting holes.
7. Proceed with wiring diagrams according to Figures 3 and 4.
8. Set DIP Switches SW1 and SW2 as desired. Refer to Figure 5, Figure 6, and
Appendix I.
9. Reconnect the LCD cable to the USB port on the main circuit board (if present).
10. Replace cover and cover plugs on the face of the unit.
CO:
Locate GSTC carbon monoxide transmitter about 5 ft (1.5 m) off the floor. Carbon
monoxide weighs about the same as air and distributes evenly throughout the
monitored space. Install GSTC CO alarm at least 15 to 20 ft (4.6 to 6.1 m) away
from boiler or fuel burning heat source. Avoid extremely dusty, dirty, humid or
greasy areas. Do not place in direct sunlight or areas subjected to extreme
temperature. Do not place in turbulent air, near fans, heat vents, air conditioners,
air returns or open windows. Blowing air may prevent CO from reaching the CO
sensor.
NO2:
NO2sensors should be mounted in the breathing zone, 4 to 6 ft (1.2 to 1.8 m) from
the floor. This is primarily because NO2is a poisonous gas which should be
detected in the area where people would be exposed to it, but also because 4 to 6
ft from the floor is an appropriate elevation to detect NO2gas.
Duct Mounting
Duct mounting kit includes an air flow pitot tube, air filter with barbed connections,
two short pieces of tubing, and one long piece of tubing.
1. Mount the pitot tube into the duct observing the flow direction marked on the pitot
tube.
2. Attach the two short pieces of tubing to the barbed connections on each side of
the air filter. See Figure 2.
3. Attach the remaining side of one of the short pieces of tubing to the barbed
connection on the transmitter.
4. Attach the remaining side of the other short piece of tubing to the high port on
the pitot tube.
5. Attach the long piece of tubing to the open barbed connection on the transmitter.
6. Attach the other end of the long tubing to the low port on the pitot tube.
WI ING
Wiring should comply with Electrical Characteristics of
Generators and Receivers for Use in Balanced Digital Multipoint
Systems, TIA-EIA-485-A-1998, Telecommunications Industry Association, 1998.
NOTICE
BACnet installations should comply with ANSI/AS RAE
Standard 135-2010 BACnet A Data Communication Protocol for
Building Automation and Control Networks, American Society of eating,
Refrigerating and Air-Conditioning Engineers, Inc., 2010.
NOTICE
MODBUS®communication protocol installations should comply
with MODBUS®communication protocol over Serial Line
Specification and Implementation Guide V1.02, MODBUS®Organization, Inc., 2006.
NOTICE
Communication wiring must be in a daisy-chain fashion. Star
connections are not permitted.
NOTICE
Cable shield must be connected to earth ground at one location
only.
NOTICE

Figure 5
Figure 6
Switch
1 - Protocol
2 - B(+) Bias Resister
3 - A(-) Bias Resister
4 - Terminating Resister
On
MODBUS®
511Ω Pull-up to 5V
511Ω Pull-down to GND
120Ω between A(-) and B(+)
Off
BACnet
Pull-up not connected
Pull-down not connected
Open
Table 1: Dip Switch SW2 Functions
Protocol
BACnet
MODBUS®
Supported Baud ates
9600
19200
38400
57600
76800
115200
Data Size
8
Table 2: Supported Configurations
Parity
None
Even
Odd
None
Stop Bits
1
1
2
Figure 7
Text
Secondary
Display
Primary
Display
Text
Numeric
Menu Name
BAC or MOD
CAL
AUT
RST
Value
xxx ADR
xxx PPM
ON
OFF
NO
YES
Description
RS-485 address (view only)
Current CO or NO2 concentration
Auto-baud will start and return to the main menu
Starts the manual serial configuration menu sequence
Will reset settings to factory default
Table 3: Standard Menu Options
Dip Switch Configurations
Use DIP Switch SW1 (see Figure 5) to configure the RS-485 address of the device.
A valid address depends on the protocol selected. Valid BACnet addresses range
from 1 to 127. Valid MODBUS®communication protocol addresses range from 1 to
247. By default, the device is shipped with MODBUS® communication protocol
selected and the address set to 127, as shown in Figure 5. A valid and unused
address should be set before connecting to an existing network. See Appendix I to
configure the required address using DIP Switch SW1. The device will not function
properly if an invalid address is set. During the power up sequence, the LCD (if
present) will display the RS-485 address as the primary value and either “BAC” to
indicate BACnet or “MOD” to indicate MODBUS® communication protocol as the
primary text. If the RS-485 address is invalid, the invalid address is shown as the
primary value with “ERR” as the primary text, and the red LED will periodically blink
once.
Use DIP Switch SW2 (see Figure 6) to configure other hardware and software
options. Table 1 shows available options. Table 2 shows supported configurations
for either BACnet or MODBUS®communication protocol.
Auto Serial Configuration
Use the auto serial configuration to enable the device to determine the baud rate,
parity, and stop bits directly from the serial traffic. After a valid RS-485 address is
chosen, the GSTC can be quickly and easily deployed. The auto serial
configuration procedure assumes a serial configuration appropriate to the chosen
protocol, shown in Table 2. Otherwise, the serial communication must be
configured manually in the setup menu.
To activate auto serial configuration, set a valid RS-485 address using DIP Switch
SW1, connect the serial bus, common and power wires, and apply power. The
device will power up and begin examining the serial bus for communication.
When the device is installed offline or away from the main network, it is necessary
to generate the appropriate traffic in order to configure the serial communication
whether BACnet or MODBUS®communication protocol is selected. While the serial
configuration is in progress, the device may not respond. The device may require
multiple read requests to complete the serial configuration process.
The auto serial configuration process is completed once a message addressed to
the device is received and processed successfully. If the serial configuration of the
bus changes, a power cycle of the device is required to restart the auto serial
configuration process.
More detailed information for BACnet protocol can be found in Appendix II, and
information for MODBUS®communication protocol can be found in Appendix III.
MENU
The menu is only shown if a display is present. Figure 7 below outlines the display
components. To enter the menu, press and hold both the SPAN and ZERO
pushbuttons for at least 3 seconds. The menu descriptions and list of the available
values for each standard menu item is shown on in Table 3. Table 4 lists the
available values for each manual menu item.
Standard Menu Descriptions
BAC or MOD: Displays the RS-485 address
CAL: Start user CO or NO2 calibration process
AUT: Auto serial configuration enabled
RST: Reset settings to factory default
Manual Menu Descriptions
BAU: Baud rate selection (only available if AUT = OFF)
PAR: Parity selection (only available if AUT = OFF)
STP: Stop bits selection (only available if AUT = OFF)
Menu Navigation
A menu flowchart, located in Appendix IV, illustrates the navigation process.
1. Press and hold the SPAN pushbutton while in the menu to move to the previous
menu item.
2. Press and hold the ZERO pushbutton while in the menu to move to the next
menu item.
3. Press and hold both the SPAN and ZERO pushbuttons for 5 seconds to activate
the current menu item. In the lower left corner of the display “SET” is shown to
indicate a setting change.
4. Press and hold either the SPAN or ZERO pushbutton to change the setting.
5. Press and hold both the SPAN and ZERO pushbuttons for 5 seconds to accept
the setting.
6. After 30 seconds of inactivity, the display will return to normal operation.

Menu Name
BAU
PAR
STP
Value
9600
19200
38400
57600
76800
115200
EVE
ODD
NON
1
2
Description
Only available if AUT = OFF
Only available if AUT = OFF
Only available if AUT = OFF
Table 4: Manual Menu Options
Sensors contain acid and are harmful if handled improperly. Do
not attempt to open sensors. Sensors should be disposed of
according to local laws.
WA NING
Figure 9
Figure 10
Switch Positions
Address Value
1
128
2
64
3
32
4
16
5
8
6
4
7
2
8
1
Table 5: DIP Switch Values
The minimum possible address would be 0 when all DIP
switches are in the “OFF” position, and the maximum possible
address would be 255 when all DIP switches are in the “ON” position. When BACnet
protocol is selected the transmitter only has valid address from 1 to 127. When
MODBUS®communication protocol is selected the transmitter only has valid address
from 1 to 247. Any address outside the selected protocol’s range will give an error.
NOTICE
Object Type
Device
Analog Input
Binary Value
Date Value
Dynamically
Creatable
No
No
No
No
Dynamically
Deletable
No
No
No
No
Object
Identifier
607xxx
AI1
BV1
DV1
DV2
Object
Name
GSTC
CO Concentration
NO2 Concentration
Zero Sensor
Calibration Date
Replace Sensor Date
Table 6: Supported BACnet Objects
SENSO EPLACEMENT
A replacement sensor is available from Dwyer Instruments, Inc.
For CO, order part number: A-505.
For NO2, order part number: A-506.
eplacing The Sensor
1. Remove the cover plugs from the face of the unit and top cover. Locate the
sensor, see Figure 1. The sensor is mounted on three pin sockets. The circuit
board is either labeled “CO SENSOR” or “NO2 SENSOR” underneath the sensor.
2. Remove and discard the used sensor.
3. Remove the shorting wire spring located at the bottom of the new sensor.
4. Install the new sensor into the three pin sockets.
5. The unit must be re-calibrated whenever a new sensor is installed.
6. Allow 30 minutes for the unit to come to temperature equilibrium prior to
calibration. The unit has internal temperature compensation, and the sensor must
be at the same temperature as the unit to calibrate properly.
CALIB ATION
Figure 8, located after Appendix III, shows how to set up a GSTC for calibration
with an auxiliary display. An auxiliary display is required for calibration unless an
LCD model of the GSTC was purchased. The procedure in Appendix IV shows how
to set the range, and calibrate the span and zero adjustments.
MAINTENANCE/ EPAI
Upon final installation of the Series GSTC, no routine maintenance is required with
the exception of sensor replacement and calibration. As with all electrochemical
type gas sensors, routine calibration is required. It is recommended that units be
re-calibrated at 6 month intervals, to maintain the published accuracy, or as
required by local ordinances or other requirements. The units will maintain 5%
accuracy if they are re-calibrated at 12 month intervals.
Except for the sensor replacement and calibration, the Series GSTC is not field
serviceable and should be returned if repair is needed. Field repair should not be
attempted and may void warranty.
WA ANTY/ ETU N
Refer to “Terms and Conditions of Sales” in our catalog and on our website.
Contact customer service to receive a Return Goods Authorization number before
shipping the product back for repair. Be sure to include a brief description of the
problem plus any additional application notes.
Appendix I: Setting the S-485 Address
The address assignment is determined by adding the values for each of the
switches that are in the “ON” position. The transmitter comes from the factory with
all of the DIP switches in the “ON” position, except position 1 as shown in Figure 9
below.
The address of the transmitter in Figure 9 is 127. This final value is determined by
adding the individual values of the DIP switches together. The values for each DIP
switch are shown below in Table 5. When adding the individual values for Figure 9,
0+64+32+16+8+4+2+1=127, which is the correct factory setting.
Another example would be if the desired address was 53. The only DIP switches
in the “ON” position would be switches 3, 4, 6, and 8 as shown in Figure 10 below.
By adding the individual values of each switch in the “ON” position,
0+0+32+16+0+4+0+1=53, the desired address is obtained.
Appendix II: BACnet Protocol
The GSTC supports objects that are listed below. Table 6 and Table 7 outlines
each item.

Property
Object Identifier
Object Name
Object Type
System Status
Vendor Name
Vendor Identifier
Model Name
Firmware Revision
Application Software
Version
Location
Description
Protocol Version
Protocol Revision
Protocol Services
Supported
Protocol Object Types
Supported
Object List
Maximum APDU Length
Accepted
Segmentation
Supported
APDU Timeout
Number of APDU
Retries
Max Master
Max Info Frames
Devices Address
Binding
Database Revision
Serial Number (1000)
Default
Value
607xxx
“GSTC 607xxx”
DEVICE (8)
Operational (0)
“Dwyer
Instruments, Inc”
607
“GSTC-C” or
“GSTC-N”
“?.?”
“?.?”
“”
“CO Detector” or
“NO2 Detector”
1
12
See pics
See Table 2
See Table 2
128
NO_SEGMENTAT
ION (3)
0
0
127
1
Empty
1
“xxxxxx”
Property Data
Type
BACnetObjectId
entifier
CharacterString
(32)
BACnetObjectT
ype
BACnetDeviceS
tatus
CharacterString
Unsigned
CharacterString
CharacterString
CharacterString
CharacterString
(32)
CharacterString
(32)
Unsigned
Unsigned
BACnetServices
Supported
BACnetObjectT
ypesSupported
BACnetArray
Unsigned
BACnetSegmen
tation
Unsigned
Unsigned
Unsigned
Unsigned
BACnetAddress
Binding
Unsigned
CharacterString
Access
Read/Write
Read/Write
Read
Read
Read
Read
Read
Read
Read
Read/Write
Read/Write
Read
Read
Read
Read
Read
Read
Read
Read
Read
Read/Write
Read
Read
Read
Read
Table 7: Object Properties
Property
Object
Identifier
Object Name
Object Type
Present Value
Status Flags
Event State
Reliability
Out of
Service
Units
Default Value
AI1
“CO Concentration” or
“NO2 Concentration”
ANALOG_INPUT (0)
Current reading
0
NORMAL (0)
NO_FAULT_DETECTED(0)
FALSE (0)
Parts-per-million (96)
Property Data Type
BACnetObjectIdentifier
CharacterString
BACnetObjectType
Real
BACnetStatusFlags
BACnetEventState
BACnetReliability
Boolean
BACnetEngineeringUnits
Table 8: Analog Input
Access
Read
Read
Read
Read
Read
Read
Read
Read/Write
Read
Property
Object
Identifier
Object Name
Object Type
Present Value
Status Flags
Event State
Reliability
Out of
Service
Default Value
BV1
“Zero Sensor”
BINARY VALUE (5)
0
0
NORMAL (0)
NO FAULT DETECTED (0)
FALSE (0)
Property Data Type
BACnetObjectIdentifier
CharacterString
BACnetObjectType
Real
BACnetStatusFlags
BACnetEventState
BACnetReliability
Boolean
Table 9: Binary Value
Access
Read
Read
Read
Read
Read
Read
Read
Read/Write
Property
Object
Identifier
Object Name
Object Type
Present Value
Status Flags
Event State
Reliability
Out of
Service
Default Value
DV1
“Calibration Date”
DATE VALUE (42)
????
{F,F,F,F}
NORMAL (0)
NO FAULT DETECTED (0)
FALSE (0)
Property Data Type
BACnetObjectIdentifier
CharacterString
BACnetObjectType
BACnetBinaryPV
BACnetStatusFlags
BACnetEventState
BACnetReliability
Boolean
Table 10: Date Value
Access
Read
Read
Read
Read/Write
Read
Read
Read
Read/Write
Property
Object
Identifier
Object Name
Object Type
Present Value
Status Flags
Event State
Reliability
Out of
Service
Default Value
DV2
“Replace Sensor Date”
DATE VALUE (42)
????
{F,F,F,F}
NORMAL (0)
NO FAULT DETECTED (0)
FALSE (0)
Property Data Type
BACnetObjectIdentifier
CharacterString
BACnetObjectType
BACnetBinaryPV
BACnetStatusFlags
BACnetEventState
BACnetReliability
Boolean
Access
Read
Read
Read
Read/Write
Read
Read
Read
Read/Write
Table 11: eplace Sensor Date
The default object identifier is 607xxx, where xxx is replaced by the address set by
the DIP Switch SW1. The object identifier value will change as the address
changes. When a specific object identifier is written via BACnet, that value is stored
and changes to the address will no longer affect the object identifier. The object
name reflects the current object identifier. When a specific object name is written
via BACnet, that value is stored and changes to the object identifier will no longer
affect the object name.
Table 8 outlines the Analog Input (AI1) object which represents the current CO or
NO2 concentration reading in parts per million.
Table 9 outlines the Binary Value (BV1) object which allows the sensor to be
remotely zeroed. When set to “ACTIVE”, the zero function will attempt to
recalibrate the zero point of the sensor.
Table 10 outlines the Date Value (DV1) object which stores the date when the
sensor was last calibrated. Since the GSTC does not track time this value must be
updated manually after calibration is performed in the field.
Table 11 outlines the Replace Sensor Date (DV2) object which stores the
suggested sensor replacement date. It is recommended to replace the sensor at
specific intervals because the sensor degrades over time. The GSTC does not
track time so this value must be updated manually after the sensor is replaced in
the field.

egister
0001
1000-1009
1010-1013
1014-1017
Description
CO or NO2 Concentration
in PPM
Model Number String
Serial Number String
Firmware Version String
Data Type
Unsigned 16 bit
integer
String
String
String
ange
0 – 500 PPM CO,
0 – 100 (0 – 10.0)
PPM NO2
“GSTC-C” or
“GSTC-N”
“xxxxxx”
“?.?”
Table 13: Input egisters
egister
0001
0500
Description
Zero Sensor
Reboot device
Data Type
Unsigned 16bit integer
Unsigned 16bit integer
ange
0 or 1
0 - Do Nothing
1 - Warm Reset
Value
0-1
0-1
Table 14: Holding egisters
Figure 8
Function Name
Read olding Registers
Read Input Registers
Write Single Register
Write Multiple Registers
Function Code
03
04
06
16
Table 12: Supported MODBUS®Functions
BACnet Services
The GSTC supports the Device Communication Control Service BIBB. The option
time duration in minutes is also supported. This device is configured with a
password that must be provided to successfully execute the command. The
password is “Dwyer”.
The GSTC also supports the Reinitialize Device Service BIBB. The supported
device states are “COLDSTART” and “WARMSTART”. All other states return an
error. This device is configured with a password that must be provided to
successfully execute the command. The password is “Dwyer”.
Appendix III: MODBUS®Communication Protocol
The GSTC supports functions and input registers that are listed below. Table 12 ,
Table 13, and Table 14 outline each item.
The string data type is read as a stream of ASCII characters with the first character
sent in the MSB of the first register and the second character sent in the LSB of the
first register and so on. If the string is shorter than the allotted size, the remaining
bytes will be zero padded.
Writing 1 to the Zero Sensor register will re-zero the sensor just as if the user has
pressed the zero pushbutton.
The Reboot Device register allows a MODBUS®communication protocol master to
remotely request this device to perform a warm reset. When a value of 1 is written
to this register the device will respond with success. The reset will take
approximately 5 seconds after the command was received. Writing a value of 0 to
this register has no effect.

ADR
PPM
MO D
CO
SEN
OK
PPM
PPM
CAL
CAL
CAL
CAL
CO
SCROLL
SCROLL
SCROLL
SCROLL
AUT
KK
AUT AUT AUT
AUT AUT
BAU BAU
SCROLL
SCROLL
SCROLL
SCROLL
SCROLL
SCROLL
SCROLL
SCROLL
SCROLL
SCROLL
PAR PAR PAR
STP STP
SET BAUD RATE
SET PARITY
SET STOP BITS
RST RST RST
NOTE - WHEN IN THE MENU, THE
DISPLAY WILL RETURN TO THE
HOME POSITION IF NO KEY IS
PRESSED WITHIN 30 SECONDS.
HOME POSITION, UNIT READS GAS
CONCENTRATION PPM
PRESS AND HOLD ZERO AND SPAN
KEYS FOR 5 SECODNS TO ENTER
THE MAIN MENU.
MODBUS/BACNET ADDRESS.
VIEWABLE ONLY.
CALIBRATION
MODE
PRESS ZERO AND SPAN TO ENTER CALIBRATION MODE
PRESS THE ZERO KEY FOR 5 SECONDS. THE
ZERO VALUE IS STORED AND THE DISPLAY
SEQUENCES TO THE SPAN GAS CALIBRATION VALUE PRESS AND HOLD THE SPAN KEY FOR 5 SECONDS
DISPLAY READS “CAL” THEN “PASS” AND RETURNS TO HOME POSITION
IF THE SENSOR OUTPUT IS NO LONGER
SUFFICIENT FOR CALIBRATION, THEN
THE DISPLAY READS “BAD SEN”. THE
SENSOR MUST BE REPLACED
PRESS AND HOLD ZERO AND SPAN UNTIL
“SET” TURNS OFF
TO ADJUST THE DISPLAY TO SET
THE DESIRED SPAN CALIBRATION VALUE,
PRESS THE DIGIT KEY TO SCROLL
THROUGH THE DIGITS. THE DIGITS WILL
BLINK AS THEY ARE SELECTED.
ADJUST THE VALUE OF THE DIGIT
USING THE VALUE KEY
HOOK UP THE UNIT TO THE SPAN CALIBRATION GAS
USING THE CALIBRATION ADAPTER A-507AS SHOW IN FIG. 8
SPAN GAS FLOW IS TO BE BETWEEN 0.5 TO 10. SLPM.
ALLOW GAS TO FLOW FOR AT LEAST 3 MINUTES.
PLACE THE UNIT IN AN AREA THAT CONTAINS FRESH
AIR (NO CO OR NO2 GAS). ALLOW 3 MINUTES TO
STABILIZE.
COMMUNICATION
SETTINGS
FACTORY SETTING IS
AUTO BAUD ON.
PRESS AND HOLD ZERO AND SPAN UNTIL
“SET” TURNS ON
PRESS ZERO OR SPAN TO SWITCH
BETWEEN AUTO BAUD ON OR OFF
AUTOBAUD MUST BE SET TO “NO” TO SET
BAUDRATE, PARITY AND STOP BIT SETTINGS
PRESS AND HOLD ZERO AND SPAN UNTIL
“SET” TURNS OFF
PRESS AND HOLD ZERO AND SPAN UNTIL
“SET” TURNS OFF
USING ZERO AND SPAN KEYS, SET BAUDRATE
TO DESIRED VALUE
PRESS AND HOLD ZERO
AND SPAN UNTIL
“SET” TURNS OFF
PRESS ZERO OR SPAN TO SWITCH
BETWEEN NO PARITY OR EVEN OR
ODD PARITY
PRESS AND HOLD ZERO AND SPAN UNTIL
“SET” TURNS ON
PRESS AND HOLD ZERO AND SPAN UNTIL
“SET” TURNS ON PRESS AND HOLD ZERO AND SPAN UNTIL
“SET” TURNS OFF
USING ZERO AND SPAN KEYS, SET STOP BIT
TO 1 OR 2
IF RESET IS SET TO YES, PRESSING ZERO AND SPAN
WILL CAUSE A FACTORY RESET, AND DISPLAY WILL
RETURN TO THE HOME POSITION
IF RESET IS SET TO NO, PRESSING ZERO AND SPAN
PRESS ZERO OR SPAN TO SWITCH
BETWEEN YES OR NO
PRESS AND HOLD ZERO AND
SPAN UNTIL “SET” TURNS ON
RESET UNIT
TO FACTORY
DEFAULTS
SCROLL TO TOP
MENU, MODBUS/BACNET
ADDRESS
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE SPAN
DIGIT
SPAN
DIGIT
ZERO
VALUE
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
SPAN
DIGIT
ZERO
VALUE
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT SPAN
DIGIT
ZERO
VALUE
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
ZERO
VALUE
SPAN
DIGIT
ZERO
VALUE
SPAN
DIGIT
SPAN
DIGIT
ZERO
VALUE
Appendix IV: Menu Flowchart and Calibration

DWYE INST UMENTS, INC. Phone: [phone] www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A. Fax: [phone] e-mail: [email protected]
©Copyright 2017 Dwyer Instruments, Inc. Printed in U.S.A. 1/17 FR# 443872-00 Rev. 5