™
detcon inc.
Detcon MicroSafe
IR-640 Carbon Dioxide Sensor (0-5%CO2)
IR642 Carbon Dioxide Sensor (10%-100%)
Operator’s Installation & Instruction Manual
November 26, 2007 • Document #2196 • Version 6.4
CAUTION:
Before operating the Model IR-640/IR-642 sensor, read this manual thoroughly and verify that
the configuration of default factory settings are appropriate and correct for your application.
The settings include: relay contact outputs (section 3.5.5d), alarm settings (section 3.5.5e and
3.9), and RS-485 ID (section 3.5.5f and 3.12).
Table of Contents
3.0 Description
3.1 Principle of Operation
3.2 Application
3.3 Specifications
3.4 Operating Software
3.5 Installation
3.6 Start-up
3.7 Calibration
3.8 Status of Programming, Alarms, Calibration Level, RS-485 ID, and Sensor Life
3.9 Programming Alarms
3.10 Program Features
3.11 RS-485 Protocol
3.12 Display Contrast Adjust
3.13 Optical Sensor Replacement
3.14 Trouble Shooting Guide
3.15 Spare Parts List
3.16 Warranty
3.17 Service Policy
3.18 Software Flow Chart
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.2
3.0 DESCRIPTION
Detcon MicroSafe™ Model IR-640, carbon dioxide gas sensors are non-intrusive “Smart” sensors designed to detect
and monitor CO2gas in air over the 0-5% range. The Detcon MicroSafe™ Model IR-642 CO2 gas sensor measures
in the 10-100% Range. One of the primary features of the sensor is its method of automatic calibration which
guides the user through each step via instructions displayed on the backlit LCD. The sensor features field
adjustable, fully programmable alarms and provides relays for two alarms plus fault as standard. The sensor comes
with two different outputs: analog 4-20 mA, and serial RS-485. These outputs allow for greater f lexibility in system
integration and installation. The microprocessor supervised electronics are packaged as a plug-in module that mates
to a standard connector board. Both are housed in an explosion proof condulet that includes a glass lens window
which allows for the display of sensor readings as well as access to the sensor’s menu driven features via a hand-held
programming magnet.
The sensor technology is a field proven “plug-in replaceable” non-dispersive infrared (NDIR) optical type. NDIR
optical sensors show an excellent response to CO2. The NDIR type sensor is characteristically stable for both span
and zero and is capable of providing reliable performance with low maintenance requirements for periods approaching 5 years in most industrial environments.
Typical ranges of detection are 0-0.30%, 0-0.50%, 0-1.00%, 0-2.00%, 0-3.00% and 0-5% with the IR640. Typical
Ranges with the IR642 are 0-10%, 0-25%, 0-50%, 0-100%. Other ranges may be accommodated and all ranges are
covered by this manual. To determine the range of detection, refer to the instructions found in section 3.8.
3.0.1 Non-dispersive Infrared (NDIR) Optical Sensor
The Detcon NDIR sensor is designed as a miniature single piece “plug-in replaceable” component, which can easily be
changed out in the field. The NDIR sensor consists of an infrared lamp source, two pyroelectric detectors, and an
optical gas sample cavity. The lamp source produces infrared radiation which interacts with CO2as it travels through
the optical gas sample cavity. The infrared radiation contacts each of two pyroelectric detectors at the completion of
the optical path. The “active” pyroelectric detector is covered by a filter specific to the part of the IR spectrum where
CO2absorbs light. The “reference” pyroelectric detector is covered by a filter specific to the non-absorbing part of the
IR spectrum. When CO2is present, it absorbs IR radiation and the signal output from the “active” pyroelectric detector decreases accordingly while the “reference” detector output remains unchanged. The ratio of the “active” and “reference” detector outputs is then used to compute CO2concentration.
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.3
3.0.2 Microprocessor Control Circuit
NC
ALARM 1
WHT
BLK
YEL
BLU
MA
VDC Power In
Optional RS-485
Terminating Resistor
Use 120 ohm
NO
NC
NO
NC
NO
NO/NC
COM
NO/NC
COM
NO/NC
COM
FAULT ALM -2 ALM -1
Alarm Dry Contacts
ALARM 2
FAULT
R1
R2
A
B
A
B
4-20 mA Output
RS-485 In
RS-485 Out
Optional 4-20 mA
Signal Developing Resistor
Use 250 ohm 1/4w
JU
M
P
E
R
S
U
N
-U
S
E
D
RED
BRN
Jumper Programmable Alarm Outputs
Normally Open or Normally Closed
Sensor
Place un-used alarm programming
jumper tabs here
detcon inc.
Program Switch #2
F
LT
A
LM
1
C
AL
MicroSafe™ CO2 Gas Sensor
HOUS TON, TEX AS
PGM 2
PGM 1
A
LM
2
M
ODEL
I
R-640
CONTRAST
Alarm & Cal LEDs
Program Switch #1
Menu Driven Display
Plug-in Microprocessor Control Circuit
Display Contrast Adjust
Porous Membrane
Optical Filter
Active Detector
Lamp
Reference Detector
Optical Sample Gas Chamber
Optical Filter
CO
2
CO
2
The control circuit is microprocessor based and is packaged as a plug-in field replaceable module, facilitating easy
replacement and minimum down time. Circuit functions include a basic sensor pre-amplifier, sensor temperature
measurement, on-board power supplies, microprocessor, back lit alpha numeric display, alarm status LED indicators, magnetic programming switches, an RS-485 communication port, and a linear 4-20 mA DC output.
3.0.3 Base Connector Board
The base connector board is mounted in the explosion proof enclosure and includes: the mating connector for the
control circuit, reverse input and secondary transient suppression, input filter, alarm relays, lugless terminals for all
field wiring, and a terminal strip for storing unused programming jumper tabs. The alarm relays are contact rated 5
amps @ 250 VAC, 5 amps @ 30 VDC and coil rated at 24 VDC. Gold plated program jumpers are used to select
either the normally open or normally closed relay contacts.
3.0.4 Explosion Proof Enclosure
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.4
The sensors are packaged in a cast metal explosion proof enclosure. The enclosure is fitted with a threaded cover
IR Lamp Source
Reference Detector Output
Active Detector Output
CO2 Not Present
CO2 Present
Principle of Operation
Sample
Gas
that has a glass lens window. Magnetic program switches located behind the transmitter module face plate are activated through the lens window via a hand-held magnetic programming tool allowing non-intrusive operator interface with the sensor. All calibration and alarm level adjustments can be accomplished without removing the cover
or declassifying the area. Electrical classification is Class I; Groups B, C, D; Div. 1.
3.1 PRINCIPLE OF OPERATION
The CO2diffuses through a sintered stainless steel f lame arrestor and into the volume of the sample gas optical
cavity. A lamp source provides a cyclical IR radiation source which travels through the optical gas sample cavity and
terminates at two pyroelectric detectors. The “active” and “reference” pyroelectric detectors each give an output
which measures the intensity of the radiation contacting their surface. The “active” pyroelectric detector is covered
by an optical filter specific to the part of the IR spectrum where CO2absorbs light. The “reference” pyroelectric
detector is covered by a filter specific to the non-absorbing part of the IR spectrum. When present, CO2absorbs a
fraction of the IR radiation and the signal output from the “active” pyroelectric detector decreases accordingly. The
signal output of the “reference” detector remains unchanged in the presence of CO2. The ratio of the “active” and
“reference” detector signal outputs is then used to compute CO2concentration. By using the ratio of the active/reference signal outputs, measurement drift caused by changes in the intensity of the lamp source and changes in the
optical path are negated.
3.1.2 Characteristics
The NDIR optical sensor element maintains strong sensitivity to CO2, as shown in the illustration below. Typical zero calibration intervals would be quarterly and typical span calibration intervals would be semi-annual to annual. However, actual
field experience is always the best determination of appropriate calibration intervals.
The MicroSafe™ IR-640/IR-642 is factory calibrated for a specific CO2 range (see section 3.8 to determine range). The detector will be factory calibrated for the range specified at time of order. If a CO2range other than that specified at time of order
is desired, contact Detcon for the appropriate field-replaceable electronics/software upgrade.
The NDIR optical sensor readings can be adversely affected by dust, dirt and oil mist accumulation as well as severe corrosion. These deposits may reduce the optical reflectivity inside the sensor, and although accurate readings are continually maintained, excessive loss in useable signal eventually gives way to noise and unstable readings. The optical sensor may, over long
periods of time (3-7 years), lose its IR lamp source filament, and in this case an optical sensor modular replacement is
required. The IR-640/IR-642 has an extensive list of Fault Diagnostics to alert and pin-point operational problems. See section
3.10
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.5
3.2 APPLICATION
Functional
Block
Diagram
Functional
Block
Diagram
Analog 4-20 mA Out
Power In
Relays Out
Pre-Amp Display
Tem per atu re
Compensation
Alarm & Fault
Relays
RS-485 & 4-20mA
Micro-
processor
Tran smit ter
Power Supply
Optical
Sensor
I/O Circuit
Protection
Serial RS-485 Out
0
4
8
12
16
20
2
0406080100
% of Range of Detection
mA DC Signal Output
Output Response Curve
Model IR-640/IR-642 MicroSafe™ sensors are designed to detect and monitor CO2gas in ambient air. Minimum sensitivity and scale resolution is 0.01%. Operating temperature range is -40° F. to +175° F. While the sensor is capable of
operating outside these temperatures, performance specifications are verified within the limit.
3.2.1 Sensor Placement/Mounting
Sensor location should be reviewed by facility engineering and safety personnel.
3.3 SPECIFICATIONS
Method of Detection
NDIR Optical
Electrical Classification
Class I; Groups B, C, D; Div. 1.
Response Time
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.6
T50 < 15 seconds; T90 < 35 seconds
Clearing Time
0% < 35 seconds
9
Repeatability
± 3% FS
Range
0 - 0.3/0.5/1/2/3/5% withthe IR-640
0-10/0-25/0-50/0-100% with the IR-642
Operating Temperature
-40° to +175° F
Accuracy
± 5% FS
Sensor Warranty
5 year pro-rated
Power Consumption
Normal operation = 95 mA (2.3 watts); Full alarm = 123 mA (<3 watts)
Zero Drift
< 0.05% per year
Output
3 relays (alarm 1, alarm 2, and fault) contact rated 5 amps @ 250 VAC, 5 amps @ 30 VDC;
Linear 4-20 mA DC; RS-485 Modbus™
Input Voltage
22.5-28 VDC
3.4 OPERATING SOFTWARE
Operating software is menu listed with operator interface via the two magnetic program switches located under the
face plate. The two switches are referred to as “PGM 1” and “PGM 2”. The menu list consists of 3 items which
include sub-menus as indicated below. (Note: see the last page of this manual for a complete software flow chart.)
01. Normal Operation
a) Current Status
02. Calibration Mode
a) Zero
b) Span
03. Program Menu
a) Program Status
b) Alarm 1 Level
c) Alarm 2 Level
d) Calibration Level
3.4.1 Normal Operation
In normal operation, the display tracks the current status of the sensor and gas concentration and appears as:
“0.00 % CO2”. The mA current output corresponds to the monitoring level and range of 0-100% FS = 4-20 mA.
3.4.2 Calibration Mode
Calibration mode allows for sensor zero and span adjustments. “1-ZERO 2-SPAN”
3.4.2.1 Zero Adjustment
Zero is set in ambient air with no CO2gas present or with zero gas applied to the sensor. “AUTO ZERO”
3.4.2.2 Span Adjustment
Unless otherwise specified, span adjustment is performed at 50% of full-scale range of CO2. “AUTO SPAN”
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.7
3.4.3 Program Mode
The program mode provides a program status menu, allows for the adjustment of alarm set point levels, and the
selection of the calibration gas level setting..
3.4.3.1 Program Status
The program status scrolls through a menu that displays:
* The gas type, range of detection and software version number. The menu item appears as: “CO2 RANGE V6.0”
* The alarm set point level of alarm 1. The menu item appears as: “ALM1 SET @ ##%”
* The alarm firing direction of alarm 1. The menu item appears as: “ALM1 ASCENDING” or descending.
* The alarm relay latch mode of alarm 1. The menu item appears as: “ALM1 NONLATCHING” or latching.
* The alarm relay energize state of alarm 1. The menu item appears as: “ALM1 DE-ENERGIZED” or energized.
* The alarm set point level of alarm 2. The menu item appears as: “ALM2 SET @ ##%”
* The alarm firing direction of alarm 2. The menu item appears as: “ALM2 ASCENDING” or descending.
* The alarm relay latch mode of alarm 2. The menu item appears as: “ALM2 LATCHING” or nonlatching.
* The alarm relay energize state of alarm 2. The menu item appears as: “ALM2 DE-ENERGIZED” or energized.
* The alarm relay latch mode of the fault alarm. The menu item appears as: “FLT NONLATCHING” or latching.
* The alarm relay energize state of the fault alarm. The menu item appears as: “FLT ENERGIZED” or deenergized.
* The calibration gas level setting. The menu item appears as: “CalLevel @ #.##%”
* Identification of the RS-485 ID number setting. The menu item appears as: “485 ID SET @ ##”
* Sensor temperature in °C appears as: “TEMPERATURE ## °C”
* The estimated remaining sensor life. The menu item appears as: “OPTICS AT 100%”
3.4.3.2 Alarm 1 Level Adjustment
The alarm 1 level is adjustable over the range 10 to 90% of full-scale range. For CO2gas sensors, the level is factory
set at 20% of full-scale range. The menu item appears as: “SET ALM1 @ #.##%”
3.4.3.3 Alarm 2 Level Adjustment
The alarm 2 level is also adjustable over the range 10 to 90% of full-scale range. For CO2 gas sensors, the level is
factory set at 60% of full-scale range. The menu item appears as: “SET ALM2 @ #.##%”
3.4.3.4 Calibration Level Adjustment
The Calibration level is adjustable from 10% to 90% of full-scale range. The menu item appears as: “CalLevel @ #.##%”
3.5 INSTALLATION
Optimum performance of ambient air/gas sensor devices is directly relative to proper location and installation practice.
3.5.1 Field Wiring Table
Detcon Model IR-640/IR-642 CO2 sensor assemblies require three conductor connection between power supplies
and host electronic controllers. Wiring designators are
conductor resistance between sensor and controller is 10 ohms. Maximum wire size for termination in the sensor
assembly terminal board is 14 gauge.
AWG Meters Feet
20 240 800
18 360 1200
16 600 2000
14 900 3000
Note 1:
Note 2: Shielded cable may be required in installations where cable trays or conduit runs include high voltage
lines or other sources of induced interference.
This wiring table is based on stranded tinned copper wire and is designed to serve as a reference only.
(4-20 mA output)
+
(DC), –(DC) , and mA(sensor signal). Maximum single
Note 3: The supply of power must be from an isolating source with over-current protection as follows:
AWG
Over-current Protection AWG Over-current Protection
Detcon Model IR-640/IR-642 Carbon Dioxide Sensor PG.8
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