CozIR®-A
Flexible Low Power CO2 Sensor
DESCRIPTION
FEATURES
The CozIR®-A is a low power NDIR CO2 sensor
using state-of-the-art solid-state LED optical
technology. The low power LEDs are
manufactured in-house, giving GSS complete
control of the CO2 sensor signal chain.
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•
•
•
•
•
The CozIR®-A’s low power consumption is
compatible with battery powered operation,
allowing the sensor to be used in a wide variety
of applications including wirelessly connected
equipment.
The sensor is available in multiple versions with
several user selectable options, including
temperature and RH measurement capability.
The CozIR®-A also features a built-in auto-zero
function that maintains CO2 measurement
accuracy over the lifetime of the product.
•
Low power CO2 sensor
30ppm typical measurement accuracy
Solid state NDIR LED optical technology
UART control and data interface
Built-in auto-zeroing
Optional Temperature and Relative
Humidity sensing
Optional Analogue (Voltage) output
APPLICATIONS
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Agriculture
Healthcare
Safety
Aerospace
Food packaging
Food storage and transportation
BLOCK DIAGRAM
T, RH and *Optional
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CozIR®-A
Flexible Low Power CO2 Sensor
TABLE OF CONTENTS
DESCRIPTION ........................................................................................................................................... 1
FEATURES ................................................................................................................................................ 1
APPLICATIONS ......................................................................................................................................... 1
BLOCK DIAGRAM ..................................................................................................................................... 1
ORDERING INFORMATION ...................................................................................................................... 4
PACKAGE DRAWING: CozIR®-A – Cased .................................................................................................. 5
PACKAGE DRAWING: CozIR®-A – Uncased ............................................................................................. 6
PIN-OUT DESCRIPTION: CozIR®-A (Both Types) ...................................................................................... 7
ABSOLUTE MAXIMUM RATINGS ............................................................................................................. 8
RECOMMENDED OPERATING CONDITIONS ............................................................................................ 8
PERFORMANCE CHARACTERISTICS ......................................................................................................... 9
HUMIDTY PERFORMANCE CHARACTERISTICS - CozIR®-A Option ......................................................... 10
TEMPERATURE PERFORMANCE CHARACTERISTICS - CozIR®-A Option ................................................ 10
CO2 ANALOGUE OUTPUT PERFORMANCE CHARACTERISTICS – CozIR®-A Option ................................ 10
ELECTRICAL CHARACTERISTICS ............................................................................................................. 11
POWER CONSUMPTION - CozIR®-A ...................................................................................................... 11
INTERFACE TIMING – NITROGEN_ZERO and FRESH_AIR_ZERO ........................................................... 12
METHOD OF OPERATION ...................................................................................................................... 13
MODE 0 COMMAND MODE .................................................................................................................. 13
MODE 1 STREAMING MODE ................................................................................................................. 13
MODE 2 POLLING MODE ....................................................................................................................... 13
DIGITAL FILTER ...................................................................................................................................... 14
ZERO POINT SETTING ............................................................................................................................ 15
ZERO IN A KNOWN GAS CONCENTRATION ........................................................................................... 15
ZERO IN NITROGEN ............................................................................................................................... 15
ZERO IN FRESH AIR ................................................................................................................................ 15
ZERO POINT ADJUSTMENT.................................................................................................................... 16
AUTO-ZERO FUNCTION ......................................................................................................................... 16
AUTO-ZERO INTERVALS......................................................................................................................... 16
AUTO-ZERO SETTINGS ........................................................................................................................... 16
ALTITUDE COMPENSATION ................................................................................................................... 17
ALTITUDE COMPENSATION TABLE ........................................................................................................ 17
CONTROL INTERFACE ............................................................................................................................ 18
CONTROL INTERFACE TIMING - UART MODE ....................................................................................... 18
UART COMMAND PROTOCOL ............................................................................................................... 18
UART OPERATION ................................................................................................................................. 18
UART INTERFACE SUMMARY ................................................................................................................ 19
CO2 LEVEL MEASUREMENT VALUE - Z INFORMATION (0x5A) .............................................................. 21
CO2 LEVEL MEASUREMENT VALUE - z INFORMATION (0x7A) .............................................................. 21
‘.’ COMMAND (0x2E) ......................................................................................................................... 21
TEMPERATURE MEASUREMENT VALUE - CozIR®-A Option .................................................................. 22
HUMIDITY MEASUREMENT VALUE - CozIR®-A Option ......................................................................... 22
K COMMAND......................................................................................................................................... 23
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CozIR®-A
Flexible Low Power CO2 Sensor
K COMMAND (0x4B) ......................................................................................................................... 23
DIGITAL FILTER COMMANDS ................................................................................................................ 23
A COMMAND (0x41) ......................................................................................................................... 23
a COMMAND (0x61) .......................................................................................................................... 23
ZERO POINT SETTING COMMANDS ...................................................................................................... 24
F COMMAND (0x46) .......................................................................................................................... 25
G COMMAND (0x47) ......................................................................................................................... 25
U COMMAND (0x55) ......................................................................................................................... 25
u COMMAND (0x75) ......................................................................................................................... 25
X COMMAND (0x58) ......................................................................................................................... 25
P COMMAND - CO2 Level for Auto-Zeroing ...................................................................................... 26
P COMMAND – CO2 Level for Zero-Point Setting .............................................................................. 26
AUTO-ZERO INTERVALS......................................................................................................................... 27
@ COMMAND (0x2E) ........................................................................................................................ 27
ALTITUDE COMPENSATION ................................................................................................................... 28
S COMMAND (0x53) .......................................................................................................................... 28
s COMMAND (0x73) .......................................................................................................................... 28
MEASUREMENT DATA OUTPUTS .......................................................................................................... 28
M COMMAND ................................................................................................................................... 29
Q COMMAND .................................................................................................................................... 29
SERIAL NUMBER AND FIRMWARE VERSION ......................................................................................... 29
Y COMMAND (0x59).......................................................................................................................... 29
CONNECTION DIAGRAM FOR UART INTERFACE ................................................................................... 30
IMPORTANT NOTICE ............................................................................................................................. 31
ADDRESS ............................................................................................................................................... 31
REVISION HISTORY ................................................................................................................................ 32
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CozIR®-A
Flexible Low Power CO2 Sensor
ORDERING INFORMATION
COZIR-A-X-XXX-X
X
2000
5000
1
X
H
Blank
X
V
Blank
Measurement Range
2,000ppm
5,000ppm
10,000ppm (1%)
Temperature and RH
Included
Not included
CO2 Voltage Output
Included
Not included
X
Temperature Range
E
Blank
Extended, -25 to 55°C
Standard
X
Casing
U
X
Uncased
Cased
Notes:
1. Sensors are shipped individually
See separate data sheet for CozIR®-A evaluation kit options
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CozIR®-A
Flexible Low Power CO2 Sensor
PACKAGE DRAWING: CozIR®-A – Cased
Bottom View
Weight = ~6g
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CozIR®-A
Flexible Low Power CO2 Sensor
PACKAGE DRAWING: CozIR®-A – Uncased
Bottom View
Weight = ~6g
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CozIR®-A
Flexible Low Power CO2 Sensor
PIN-OUT DESCRIPTION: CozIR®-A (Both Types)
PIN
1
2
3
4
5
6
7
8
NAME
GND
NC
VDD
GND
Rx_In
GND
Tx_Out
NITROGEN_ZERO
TYPE
Supply
Unused
Supply
Supply
Digital Input
Supply
Digital Output
Digital Input
9
10
ANALOGUE_OUTPUT Analogue Output
FRESH_AIR_ZERO
Digital Input
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DESCRIPTION
Sensor ground
Do Not Connect
Sensor supply voltage
Sensor ground
UART Receive Input
Sensor ground
UART Transmit Output
Set low to initiate a Zero in Nitrogen
Calibration Cycle
CO2 Level (Optional)
Set low to initiate a Zero in Fresh Air
Calibration Cycle
Production Data, Revision 4.4, 1 February 2021
Copyright © 2021 Gas Sensing Solutions Ltd.
CozIR®-A
Flexible Low Power CO2 Sensor
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are stress ratings only. Permanent damage to the CozIR®-A may be
caused by continuously operating at or beyond these limits. The CozIR®-A functional operating limits
and guaranteed performance specifications are given at the test conditions specified.
ESD Sensitive Device. This sensor uses ESD sensitive components. It is
therefore generically susceptible to damage from excessive static voltages.
Proper ESD precautions must be taken during handling and storage of this
device.
CONDITION
Supply Voltages
Voltage Range Digital Inputs
Operating Temperature Range (Ta)
- Standard
- Extended
Storage Temperature Range
Humidity Range (RH), Non
Condensing
Operating Ambient Pressure Range
MIN
-0.3V
GND -0.3V
MAX
+6.0V
5V
0°C
-25°C
-40°C
0
+50°C
+55°C
+70°C
95%
500mbar
2bar
RECOMMENDED OPERATING CONDITIONS
PARAMETER
Supply
Ground
SYMBOL
VDD
GND
MIN
3.25
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TYP
3.3
0
MAX
5.5
UNIT
V
V
Production Data, Revision 4.4, 1 February 2021
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CozIR®-A
Flexible Low Power CO2 Sensor
PERFORMANCE CHARACTERISTICS
Test Conditions Unless Otherwise Specified
VDD = 3.3V, GND = 0V. CO2 = 450ppm, RH = 0% non-condensing, T= 25°C, Pressure = 1013mbar
PARAMETER
CO2 measurement
range
SYMBOL TEST
CONDITIONS
Accuracy
CO2 RMS Noise
Time to Valid
Measurement After
Power-On
Response Time
Repeatability
Pressure
Dependence
Current
Consumption
@25°C
0
0
0
0°C to +55°C, after
zeroing @25°C
Dependent on
digital filter setting
From 0ppm to T90
(half full-scale),
default settings,
limited by diffusion
through membrane
window
Per mbar deviation
from 1013mbar,
950-1050mbar
Peak current when
sampling
Peak at turn-on
SLEEP Mode
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0.3
TYP
±(30, +3%)
of reading
±(30, +3%)
3.3
MAX
UNIT
2,000
5,000
10,000
ppm
ppm
ppm
±(50, +3%)
of reading
6.5
ppm
ppm
ppm
secs
30
secs
±30, +3%,
0.14
ppm
%
15
mA
40
0.01
mA
mA
Production Data, Revision 4.4, 1 February 2021
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CozIR®-A
Flexible Low Power CO2 Sensor
HUMIDTY PERFORMANCE CHARACTERISTICS - CozIR®-A Option
PARAMETER
SYMBOL
Humidity
measurement
range
Accuracy
Repeatability
Response time
Accuracy drift
TEST
CONDITIONS
MIN
TYP
MAX
UNIT
100
%
0
@25°C
±3
% RH
@25°C
±1
10
0.03
%
secs
%/Yr
0-50%, @25°C
CO2 ANALOGUE OUTPUT PERFORMANCE CHARACTERISTICS – CozIR®-A Option
PARAMETER
SYMBOL
Output voltage
range1, 2
ANALOGUE_OUTPUT
CO2 level
Repeatability
Response time
TEST
CONDITIONS
0-1%
@25°C
From 0ppm to T90
default settings
MIN
TYP
0
MAX
VDD
33
±0.1
0.5
UNIT
V
uV/ppm
%
secs
Notes
1. The output CO2 accuracy is degraded where ANALOGUE_OUTPUT VDD–50mV
2. ANALOGUE_OUTPUT accuracy specified with a resistive loading @ >100Kohm
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CozIR®-A
Flexible Low Power CO2 Sensor
ELECTRICAL CHARACTERISTICS
PARAMETER
Digital Input/Output
Input HIGH Level
Input LOW Level
Output HIGH Level
Output LOW Level
SYMBOL TEST
CONDITIONS
MIN
TYP
MAX
UNIT
1.0
3.0
0.4
V
V
V
V
1.8
IOH = +1mA
IOL = -1mA
2.6
POWER CONSUMPTION - CozIR®-A
Test Conditions Unless Otherwise Specified
VDD = 3.3V, GND = 0V. CO2 = 450ppm, RH = 0% non-condensing, T= 25°C, Pressure = 1013mbar
SETTING
SYMBOL TEST CONDITIONS
OFF
Active, K0 SLEEP
mode, no
measurement
Active, K1 mode
whilst taking CO2
2 measurements
Additional with
RH active
Additional with T
active
Additional with
CO2 active
3.3
I (mA)
0
0.01
Total
Power
mW
0
0.03
3.3
1
3.5
RH measurement on
+0.05
+0.2
Temperature
measurement on
With analogue CO2
output
+0.05
+0.2
+0.02
+0.1
No power applied
Default settings
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VDD
V
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CozIR®-A
Flexible Low Power CO2 Sensor
INTERFACE TIMING – NITROGEN_ZERO and FRESH_AIR_ZERO
PARAMETER
Power On to NITROGEN_ZERO
Ready
NITROGEN_ZERO Low Pulse-Width
Control Interface Setup Time
SYMBOL
t1
t2
t3
MIN
Time to
stable gas
3
600
TYP
MAX
UNIT
ms
s
ns
Notes
1. The timing for FRESH_AIR_ZERO is identical to NITROGEN_ZERO
2. Ensure gas concentration is stable (t1) before beginning zeroing process
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CozIR®-A
Flexible Low Power CO2 Sensor
METHOD OF OPERATION
After power is applied to the CozIR®-A, the sensor will automatically start to take CO2 measurements
using the Mode 1 default settings, where the sensor is pre-programmed to send CO2 measurement
data at 2 readings per second.
The measurement rate is fixed at 2 readings per second at a fixed 9600 baud rate. The sensor will
return the previous CO2 measurement results if the user requests more frequent measurements.
The CozIR®-A family has 3 potential modes of operation.
MODE 0 COMMAND MODE
In this mode, the sensor is in a SLEEP mode, waiting for commands. No measurements are made.
There is no latency in command responses. All commands that report measurements or alter the
zero-point settings are disabled in Mode 0. Mode 0 is NOT retained after power cycling.
MODE 1 STREAMING MODE
This is the factory default setting. Measurements are reported twice per second. Commands are
processed when received, except during measurement activity, so there may be a time delay of up
to 10ms in responding to commands.
MODE 2 POLLING MODE
In polling mode, the sensor only reports readings when requested. The sensor will continue to take
measurements in the background, but the output stream is suppressed until data is requested. The
sensor will always power up in streaming or polling mode, whichever mode was used before the
power cycle.
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CozIR®-A
Flexible Low Power CO2 Sensor
DIGITAL FILTER
The CO2 gas chamber is illuminated with a nominal 4.25um wavelength LED and the signal received
using a photo-diode. The signal from the photo-diode is processed and filtered by the sensor to
remove noise and provide an accurate CO2 reading. High frequency noise coming from the sampling
process is removed using a proprietary lowpass filter. The digital filter setting can be varied,
allowing the user to reduce measurement noise at the expense of the measurement response time.
The ideal digital filter setting is application specific and is normally a balance between CO2 reading
accuracy and response time. The CozIR®-A sensor will also output the raw unfiltered CO2
measurement data. This data can be post processed using alternative filter algorithms.
Filter Effect on Measurement Data Outputs
900
800
CO2 Levels (ppm)
700
600
500
400
Filtered (Z)
300
Unfiltered (z)
200
100
0
1
11
21
41
31
51
# Measurements
The graph above shows the effects of the filter on the CO2 measurement data (Z or z). The unfiltered
output is shown in orange and the filtered output shown in blue.
Filter Response vs. Filter Setting
4500
4000
CO2 Level (ppm)
3500
A=16
3000
A=32
2500
A=64
A=128
2000
T90
1500
1000
500
0
0
50
100
150
200
250
300
350
400
# Measurements
The graph above shows the effect of the filter on response times. Increasing the filter setting
increases the measurement output response time. T90 is the time to 90% of reading. The CozIR®-A
takes 2 readings per second.
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CozIR®-A
Flexible Low Power CO2 Sensor
ZERO POINT SETTING
There are a several methods available to the user to set the zero point of the sensor. The
recommended user method is zero-point setting in a known gas concentration. In all cases, the best
zero is obtained when the gas concentration is stable, and the sensor is at a stabilised temperature.
Note that zero-point settings are not cumulative and only the latest zero-point setting is effective.
For example, there is no benefit in zeroing in nitrogen, and then zeroing in a calibration gas. The
sensor will store only the latest zero point.
To improve zeroing accuracy, the recommended digital filter setting is 32. See the ‘A’ command.
ZERO IN A KNOWN GAS CONCENTRATION
Place the sensor in a known gas concentration, power up the sensor and allow time for the sensor
temperature to stabilise, and for the gas to be fully diffused into the sensor.
Send the ZERO IN A KNOWN GAS CONCENTRATION command X to the sensor. The sensor will be
zeroed using the known gas concentration level sent by the user. The concentration value written to
the sensor must be scaled dependent on the sensor CO2 measurement range. The multiplier for the
scaling factor is set according to the range of the sensor, see the ‘.’ command.
ZERO IN NITROGEN
Place the sensor in nitrogen gas and allow time for the sensor temperature to stabilise and the gas
to be fully diffused into the sensor. Send the ZERO IN NITROGEN command U to the sensor. The
sensor is zeroed assuming a 0ppm CO2 environment.
This function can also be enabled in hardware by pulling the NITROGEN_ZERO pin low for greater
than 3 seconds (CozIR®-A Only).
ZERO IN FRESH AIR
If there is no calibration gas or nitrogen available, the sensor zero point can be set in fresh air.
Ambient CO2 concentrations in fresh air are typically 400ppm. The CO2 concentration fresh air zero
level is programmable over a range from 0ppm to the full scale of the sensor.
Place the sensor in a fresh air environment and allow time for the sensor temperature to stabilise,
and for the fresh air to be fully diffused into the sensor. Power up the sensor, write the G command
to the sensor. The concentration value written to the sensor must be scaled dependent on the
sensor CO2 measurement range. The sensor can use the default fresh air CO2 concentration value
(400ppm), or the user can write a different fresh air value to the sensor if desired.
This function can also be enabled in hardware by pulling the FRESH_AIR_ZERO pin low for greater
than 3 seconds.
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CozIR®-A
Flexible Low Power CO2 Sensor
ZERO POINT ADJUSTMENT
If the CO2 concentration and the sensor reported concentration are known, the zero point can be
adjusted using the known concentration to fine tune the zero point. For example, if the sensor has
been in an environment that has been exposed to outside air, and the sensor reading is known at
that time, the zero point can be fine-tuned to correct the reading. This is typically used to
implement automated zeroing routines.
The known CO2 concentration value and the reported CO2 value from the sensor can be sent to the
sensor using the ZERO POINT ADJUSTMENT command F.
AUTO-ZERO FUNCTION
The sensor has a built-in auto-zero function. To function correctly, the sensor must be exposed to
typical background levels (400-450ppm) at least once during the auto-zero period. For example,
many buildings will drop quickly to background CO2 levels when unoccupied overnight or at
weekends. The auto-zero function uses the information gathered during these periods to re-zero.
The sensor will reset the ‘zero’ level every time it does an auto-zero. Auto-zero is disabled by
default. If the sensor is powered down, the auto-calibration is reset to default values.
The auto-calibration function works in the same way as the ZERO IN FRESH AIR command. Autozero is disabled by default, but can be enabled to operate automatically, or can be forced. The user
can also independently adjust the CO2 level used for auto-zeroing. Typically, it is set to the same
value as the ZERO IN FRESH AIR value, but it can also be set at a different level if desired.
AUTO-ZERO INTERVALS
The auto-zero period can be programmed by the user. The sensor can be programmed to undertake
an initial auto-zero after power-on. Thereafter, the auto-zero period can be set independently of
the start-up auto-zero time. Note, the auto-zero settings are reset if the sensor is powered down.
AUTO-ZERO SETTINGS
By default, the sensor will automatically ‘zero’ using the measured CO2 level sampled during the
auto-zero period. The user can alter the behaviour of the sensor as a result of the auto-zero process.
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CozIR®-A
Flexible Low Power CO2 Sensor
ALTITUDE COMPENSATION
NDIR gas sensors detect the concentration of gas by measuring the degree of light absorption by the
gas analyte. The degree of light absorption is then converted into a concentration reported by the
sensor.
The absorption process is pressure dependent, and a change in pressure will cause a change in the
reported gas concentration. As the pressure increases, the reported gas concentration also
increases. As the pressure decreases, the reported concentration decreases. This effect takes place
at a molecular level and is common to all NDIR gas sensors.
GSS sensors are calibrated at 1013mbar. The reading will vary by approximately 0.14% of reading for
each mbar change in barometric pressure.
If the sensor is installed at an elevated altitude, the mean barometric pressure will be lower than
1013mbar. It is possible to configure the sensor to correct for this effect, by setting the altitude
compensation value as part of the initial set up process. This will apply a permanent correction to
the output of the sensor, depending on the altitude setting selected.
ALTITUDE COMPENSATION TABLE
Altitude
(ft.)
Altitude
(m)
Pressure
(mbar)
Sea Level
Difference
%
Change
per
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
6,000
7,000
8,000
9,000
10,000
0
153
305
458
610
763
915
1,068
1,220
1,373
1,525
1,830
2,135
2,440
2,745
3,050
1,013
995
977
960
942
925
908
891
875
859
843
812
782
753
724
697
0
18
36
53
71
88
105
122
138
154
170
201
231
260
289
316
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
CO2
Measurement
Change (%)
0
3
5
7
10
12
15
17
19
22
24
28
32
36
40
44
Compensation
Value
8,192
8,398
8,605
8,800
9,006
9,201
9,396
9,591
9,775
9,958
10,142
10,497
10,841
11,174
11,506
11,816
Other altitude compensation values can be calculated using the following formula.
𝑺𝑺𝑺𝑺𝑺𝑺 𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳 𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫 ∗ 𝟎𝟎. 𝟏𝟏𝟏𝟏
� ∗ 𝟖𝟖𝟖𝟖𝟖𝟖𝟖𝟖
𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪 𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽𝑽 = 𝟖𝟖𝟖𝟖𝟖𝟖𝟖𝟖 + �
𝟏𝟏𝟏𝟏𝟏𝟏
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CozIR®-A
Flexible Low Power CO2 Sensor
CONTROL INTERFACE
The CozIR®-A family of sensors are controlled by writing and reading from the sensor via its UART
interface. The Rx_In and Tx_Out pins are normally high, suitable for direct connection to a UART. If
the sensor is to be read by a true RS232 device (e.g. a PC), it is necessary to pass through a level
converter to step up/down the voltage and invert the signal.
CONTROL INTERFACE TIMING - UART MODE
PARAMETER
Baud Rate
Data Bits
Parity
Stop Bits
Hardware Flow Control
SYMBOL
MIN
TYP
9600
8
None
1
None
MAX
UNIT
Bits/s
UART COMMAND PROTOCOL
All UART commands must be terminated with a carriage return and line feed , hex 0x0D
0x0A. In this document, this is shown as ‘\r\n’. UART commands that take a parameter always have
a space between the letter and the parameter. The sensor will respond with a ‘?’ if a command is
not recognised. The two most common causes are missing spaces or missing terminators.
All command communications are in ASCII and are terminated by carriage return, line feed (0x0D
0x0A). This document uses the protocol “\r\n” to indicate the carriage return line feed. All
responses from the sensor, including measurements, have a leading space (ASCII character 32).
The character ‘#’ represents an ASCII representation of a numeric character (0-9). Note there is a
space between the first letter and any parameter. For example, the X command reads “X space 2000
carriage return line feed”.
UART OPERATION
When initially powered, the sensor will immediately start to transmit a CO2 reading on receiving any
character.
The CO2 measurement is reported as:
Z #####\r\n
where Z ##### shows the CO2 concentration.
Note that all outputs from the sensor have a leading space.
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CozIR®-A
Flexible Low Power CO2 Sensor
UART INTERFACE SUMMARY
Syntax
Use
Example
Response
A ###\r\n
Set value of the
digital filter
Return the value of
the digital filter
Fine Tune the zeropoint setting
Zero-point setting
using fresh air
Returns the relative
humidity value
Switches the sensor
between different
modes
Sets the number of
measurement data
types output by the
sensor
Sets value of CO2
background
concentration in ppm
for auto-zeroing
A 128\r\n
A 00128\r\n
See “Digital Filter”
a\r\n
a 00128\r\n
See “Digital Filter”
F 410 400\r\n
F 33000\r\n
G\r\n
G 33000\r\n
See “Zero Point
Setting”
See “Zero Point
Setting”
Only if fitted as an
option
Sets value of CO2
background
concentration in ppm
used for zero- point
setting in fresh air.
P 10 1\r\n
P 11 144\r\n
Reports the latest
measurement data
types, as defined by
‘M’
Sets the pressure and
concentration
compensation value
Returns the altitude
compensation value
Returns the
temperature value
Zero-point setting
using nitrogen
Manual setting of the
zero point.
Zero-point setting
using a known gas
calibration
Return firmware
version and sensor
serial number
Q\r\n
H 12345 T 12345 Z
00010\r\n
S 8192\r\n
S 08192\r\n
See “Altitude
Compensation”
s\r\n
s 08192\r\n
See “Altitude
Compensation”
Only if fitted as an
option
See “Zero Point
Setting”
See “Zero Point
Setting”
See “Zero Point
Setting”
a\r\n
F ##### #####\r\n
G\r\n
H\r\n
K #\r\n
M ###\r\n
P 8 ###\r\n
P 9 #\r\n
P 10 ###\r\n
P 11 #\r\n
Q\r\n
S #####\r\n
s\r\n
T\r\n
U\r\n
u #####\r\n
X #####\r\n
Y\r\n
H 00551\r\n
K 1\r\n
K 1\r\n
M 212\r\n
M 212\r\n
See “Output Fields”
P 8 1\r\n
P 9 144\r\n
Two-byte value,
P 8 = MSB
P 9 = LSB
400ppm in the
example
Two-byte value,
P 8 = MSB
P 9 = LSB
400ppm in the
example
T 01224\r\n
U\r\n
U 33000\r\n
u 32997\r\n
u 32997\r\n
X 2000\r\n
X 32997\r\n
Y\r\n
Returns two lines
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CozIR®-A
Flexible Low Power CO2 Sensor
Syntax
Use
Example
Response
Z\r\n
Return the most
recent filtered CO2 2
measurement in ppm
Return the most
recent unfiltered CO2
2 measurement in
ppm
Sets the timing for
initial and interval
auto-zero periods
Returns the autozero configuration
Switch Auto-zero on
or off
Returns the scaling
factor multiplier
required to convert
the Z or z output to
ppm
Z\r\n
Z 01521\r\n
z\r\n
Z 01521\r\n
@ 1.0 8.0\r\n
@ 1.0 8.0\r\n
See “Auto-Zero
Function” for details
@ 1.0 8.0\r\n
@ 1.0 8.0\r\n
@ 0\r\n
@ 0\r\n
.\r\n
. 00010\r\n
See “Auto-Zero
Function” for details
See “Auto-Zero
Function” for details
Multiply by 10 in the
example
z\r\n
@ #.# #.#\r\n
@ r\n
@ #r\n
.\r\n
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Comments
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CozIR®-A
Flexible Low Power CO2 Sensor
CO2 LEVEL MEASUREMENT VALUE - Z INFORMATION (0x5A)
Description
Syntax
Example
Response
Reports the latest filtered CO2 measurement
ASCII Character 'Z', terminated by 0x0D 0x0A (CR & LF)
Z\r\n
Z 00521\r\n
This value needs to be multiplied by the appropriate scaling factor to derive the ppm value. See the
‘.’ command.
CO2 LEVEL MEASUREMENT VALUE - z INFORMATION (0x7A)
The sensor is also capable of reporting the real time unfiltered CO2 measurement value.
Description
Syntax
Example
Response
Reports the unfiltered CO2 measurement
ASCII Character 'Z', terminated by 0x0D 0x0A (CR & LF)
z\r\n
z 00521\r\n
‘.’ COMMAND (0x2E)
To calculate the measurement value in ppm, the ‘Z’ or ‘z’ value, they must be converted into ppm by
using the ‘.’ multiplier factor. This multiplier will depend on the full-scale measurement range of the
sensor. The multiplier is related to the full-scale range of the sensor.
The multiplier must also be used when sending CO2 concentration levels to the sensor, for example
when setting the fresh air CO2 concentration value. The ‘.’ Command can also be used to read back
the scaling factor.
For example, if the user wants to zero the sensor in a known concentration of gas (e.g. 450ppm), the
value written to the sensor must be 450/scaling factor.
Description
Syntax
Example
Response
Returns a number indicating what multiplier must be applied to the Z CO2
measurement output to convert it into ppm.
ASCII character '.', terminated by 0x0D 0x0A ( CR & LF )
.\r\n
. 00010\r\n
(this number is variable, usually 10)
Measurement
Range of Sensor
CO2 Measurement
Scaling Factor (Z)
CO2 Measurement
Output Units
Example
0 – 60%
10
ppm/10
Z 01200 = 12000ppm = 1.2%
0 – 100%
100
ppm/100
Z 01500 = 15000ppm = 15%
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CozIR®-A
Flexible Low Power CO2 Sensor
TEMPERATURE MEASUREMENT VALUE - CozIR®-A Option
Command
Use
Example
Response
Comments
T\r\n
Returns the most
recent temperature
measurement.
T #####\r\n
T 01224\r\n
Where ##### is a 5-digit number.
Temperature (°C) = (##### - 1000)/10.
22.4°C in the example
Description
Syntax
Example
Response
Returns the most recent temperature measurement.
ASCII character 'T', SPACE, decimal, terminated by 0x0D 0x0A ( CR & LF )
T\r\n
T 01224\r\n
(this number is variable)
HUMIDITY MEASUREMENT VALUE - CozIR®-A Option
Command
Use
Example
Response
Comments
H\r\n
Return the most
recent humidity
measurement.
H #####\r\n
H 00551\r\n
Where ##### is a 5-digit
number.
Humidity (%RH) = #####/10.
55.1% RH in the example
Description
Syntax
Example
Response
Returns the most recent the humidity measurement.
ASCII character 'H', SPACE, decimal, terminated by 0x0D 0x0A ( CR & LF )
H\r\n
H 00551\r\n
(this number is variable)
Note both temperature and humidity outputs are a factory fit option on the CozIR®-A only. If not
fitted, sensor will return either T 00000 or H 00000.
The sensor default data output is filtered CO2 only. To output temperature, humidity, and filtered
CO2, send “M 4164\r\n” (see “Output Fields”).
The output format will have the form: H 00345 T 01195 Z 00065\r\n
This example indicates 34.5% RH, 19.5°C and 650ppm CO2.
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CozIR®-A
Flexible Low Power CO2 Sensor
K COMMAND
Command
Use
Default
K #\r\n
Switches the
sensor between
different control
modes
1
Range
Example
Response
Comments
K 1\r\n
K 1\r\n
See ‘K’ Commands
K COMMAND (0x4B)
Description
Syntax
Sets the control interface mode
ASCII character 'K', SPACE, mode number, terminated by 0x0D 0x0A (CR &
LF)
K 1\r\n
K 00001\r\n
(this number is variable)
Example
Response
DIGITAL FILTER COMMANDS
Command
Use
Default
Range
Example
Response
A ###\r\n
Set value of the
digital filter
16
065635
A 16\r\n
A 00016\r\n
a\r\n
Return value of
digital filter
065365
a\r\n
a 00016\r\n
Comments
A COMMAND (0x41)
Description
Syntax
Example
Response
Set the value for the digital filter
ASCII character 'A', SPACE, decimal, terminated by 0x0D 0x0A (CR & LF)
A 16\r\n
A 00016\r\n
(this number is variable)
a COMMAND (0x61)
Description
Syntax
Example
Response
Set the value for the digital filter
ASCII character 'A', SPACE, decimal, terminated by 0x0D 0x0A (CR & LF)
A 16\r\n
A 00016\r\n
(this number is variable)
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CozIR®-A
Flexible Low Power CO2 Sensor
ZERO POINT SETTING COMMANDS
Command
Use
F #####
#####\r\n
Fine Tune the
zero point
G\r\n
Range
Example
Response
Comments
Range of
sensor
F 410
400\r\n
F 33000\r\n
See “Zero Point
Setting”
Zero-point
setting using
fresh air
G\r\n
G 33000\r\n
See “Zero Point
Setting”
U\r\n
Zero-point
setting using
nitrogen
U\r\n
U 33000\r\n
See “Zero Point
Setting”
u #####\r\n
Manual setting
of the zero
point
u
32997\r\n
u 32997\r\n
See “Zero Point
Setting”
X #####\r\n
Zero-point
setting using a
known gas
concentration
X 2000\r\n
X 32997\r\n
See “Zero Point
Setting”
P 8 ###\r\n
P 9 #\r\n
Sets value of
CO2
background
concentration
in ppm for
auto-zeroing
P 8 1\r\n
P 9 144\r\n
Sets value of
CO2
background
concentration
in ppm used
for zero- point
setting in fresh
air.
P 10 1\r\n
P 11 144\r\n
P 10 ###\r\n
P 11 #\r\n
Default
Range of
sensor
400ppm in the
example
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Two-byte value,
P 8 = MSB
P 9 = LSB
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Two-byte value,
P 8 = MSB
P 9 = LSB
400ppm in the
example
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CozIR®-A
Flexible Low Power CO2 Sensor
F COMMAND (0x46)
Description
Syntax
Example
Response
Sets the zero-point using a known reading and a known CO2 concentration
terminated by 0x0D 0x0A (CR & LF)
ASCII character 'F', SPACE, then the reported gas concentration, SPACE, then
the actual gas concentration, terminated by 0x0D 0x0A (CR & LF)
F 41 39\r\n
F 33000\r\n
(the numbers are variable)
G COMMAND (0x47)
Description
Syntax
Example
Response
Sets the zero point assuming the sensor is in fresh air (typically 400ppm CO2,
but level can be set by user – see P commands.)
ASCII character 'G' terminated by 0x0D 0x0A (CR & LF)
G\r\n
G 33000\r\n
(the number is variable)
U COMMAND (0x55)
Description
Syntax
Example
Response
Sets the zero point assuming the sensor is in 0ppm CO2 such as nitrogen.
ASCII Character 'U' terminated by 0x0D 0x0A (CR & LF)
U\r\n
U 32767\r\n(the number is variable)
u COMMAND (0x75)
Description
Syntax
Example
Response
Forces a specific zero set point value.
Input value is scaled by CO2 value multiplier, see ‘.’ command.
ASCII character 'u', SPACE, then the gas concentration, terminated by 0x0D
0x0A (CR & LF)
u 32767\r\n
u 32767\r\n
X COMMAND (0x58)
Description
Syntax
Example
Response
Sets the zero point with the sensor in a known concentration of CO2. Input
value is scaled by CO2 value multiplier, see ‘.’ command.
ASCII character 'X', SPACE, then the gas concentration, terminated by 0x0D
(CR & LF)
X 1000\r\n
X 33000\r\n
(the number is variable).
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CozIR®-A
Flexible Low Power CO2 Sensor
P COMMAND - CO2 Level for Auto-Zeroing
Description
Syntax
Example
Response
Sets the value of CO2 in ppm used for auto-zeroing.
Input value is scaled by CO2 value multiplier, see ‘.’ command.
ASCII character 'P', SPACE, then 8, SPACE, then MSB terminated by 0x0D
0x0A (CR & LF)
ASCII character 'P' then a space, then 9, then a space, then LSB terminated
by 0x0D 0x0A (CR & LF)
P 8 0\r\n
P 9 40\r\n
p 8 0\r\n
p 9 40\r\n
The value is entered as a two-byte word, MSB first.
MSB = Integer (Concentration/256)
LSB = Concentration – (256*MSB)
In the above example, target CO2 background concentration is 400ppm.
MSB = Integer (400/256) = 1
LSB = 400 – 256 = 144
P COMMAND – CO2 Level for Zero-Point Setting
Description
Syntax
Example
Response
Sets value of CO2 in ppm for zero-point setting in fresh air.
Input value is scaled by CO2 value multiplier, see ‘.’ command.
ASCII character 'P', SPACE, then 10, SPACE, then MSB terminated by 0x0D
0x0A (CR & LF)
ASCII character 'P', SPACE, then 11, SPACE, then LSB terminated by 0x0D
0x0A (CR & LF)
P 10 7\r\n
P 11 208\r\n
p 10 7\r\n
p 11 208\r\n
MSB = Integer (Concentration/256)
LSB = Concentration – (256*MSB)
In the above example, target zero-point CO2 concentration is 2000ppm.
MSB = Integer (2000/256) = 7
LSB = 2000 – (256*MSB) = 208
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CozIR®-A
Flexible Low Power CO2 Sensor
AUTO-ZERO INTERVALS
UART
Command
Use
Default
@ #.# #.#\r\n
Auto-zero
interval
settings
Range
Example
Response
Comments
@ 1.0 8.0\r\n
@ 1.0 8.0\r\n
See “Auto-zero”
for details
@ COMMAND (0x2E)
Description
Syntax
Example
Response
Set the ‘Initial Interval’ and ‘Regular Interval’ for auto-zero events.
ASCII character '@', SPACE, decimal, SPACE, decimal terminated by 0x0D
0x0A (CR & LF)
@ 1.0 8.0\r\n
@ 1.0 8.0\r\n (the number mirrors the input value)
Both the initial interval and regular interval are given in days. Both must be entered with a decimal
point and one figure after the decimal point. In the above example, the auto-zeroing interval is set to
8 days, and the initial interval set to 1 day.
To disable auto-zeroing, send @ 0\r\n.
To start an auto-zeroing immediately, send 65222\r\n.
To determine the auto-zeroing configuration, send @\r\n.
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Flexible Low Power CO2 Sensor
ALTITUDE COMPENSATION
UART
Command
Use
Default Range
Example
Response
Comments
S #####\r\n
Sets the altitude
compensation value
8192
S 8192\r\n
S 08192\r\n
See “Altitude
Compensation”
s\r\n
Returns the altitude
compensation value
s\r\n
s 08192\r\n
See “Altitude
Compensation”
0-65536
S COMMAND (0x53)
Description
Syntax
Example
Response
Set the ‘Altitude Compensation' value
ASCII character 'S', SPACE, decimal, terminated by 0x0D 0x0A (CR & LF)
S 8192\r\n
S 8192\r\n
(the number mirrors the input value)
s COMMAND (0x73)
Description
Syntax
Example
Response
Reports the ‘Altitude Compensation' value.
ASCII Character 's', terminated by 0x0D 0x0A (CR & LF)
s\r\n
s 8192\r\n
MEASUREMENT DATA OUTPUTS
The CozIR®-A family of sensors can be configured to provide CO2, temperature, and humidity data as
a single string of data.
UART
Command
Use
Default
M #####\r\n
Sets the number of
measurement data
types output by
the sensor. #####
is the mask value
M 04164\r\n
Measurement Parameter
Humidity
Temperature
CO2 (Filtered)
CO2 (Unfiltered)
Range
Field Identifier
H
T
Z
z
Example
Response
Comments
See “Output
Fields”
M #####\r\n
Sets the number of
measurement data
types output by
the sensor
Mask Value
4096
64
4
2
The required mask value is the sum of the ‘Mask Value’ for each field required. To output filtered
and unfiltered CO2 data, set M=6.
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CozIR®-A
Flexible Low Power CO2 Sensor
M COMMAND
Description
Syntax
Example
Response
Sets the type and number of data outputs
ASCII character 'M', terminated by 0x0D 0x0A ( CR & LF )
M\r\n
M 04164\r\n
Q COMMAND
Description
Syntax
Reports the output data fields
ASCII character 'Q', SPACE, then Mask Value, terminated by 0x0D 0x0A ( CR
& LF )
Q\r\n
H 12345 T 12345 Z 00010\r\n
Example
Response
SERIAL NUMBER AND FIRMWARE VERSION
UART
Command
Use
Default Range
Y\r\n
Return
firmware
version and
sensor serial
number
Example
Response
Y\r\n
Returns two
lines
Comments
Y COMMAND (0x59)
Description
Syntax
Example
Response
The present version string for the firmware and serial number of the sensor.
ASCII character 'Y', terminated by 0x0D 0x0A ( CR & LF )
Y\r\n
Y,Jan 30 2013,10:45:03,AL17\r\n
ingB 00233 00000\r\n
N.B. This command returns two lines split by a carriage return line feed and terminated by a carriage
return line feed. This command requires that the sensor has been stopped (see ‘K’ command).
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CozIR®-A
Flexible Low Power CO2 Sensor
CONNECTION DIAGRAM FOR UART INTERFACE
SENSOR SLAVE
Rx_IN
Tx_OUT
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UART MASTER
Tx_OUT
Rx_IN
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CozIR®-A
Flexible Low Power CO2 Sensor
IMPORTANT NOTICE
Gas Sensing Solutions Ltd. (GSS) products and services are sold subject to GSS’s terms and conditions of sale,
delivery and payment supplied at the time of order acknowledgement. GSS warrants performance of its
products to the specifications in effect at the date of shipment. GSS reserves the right to make changes to its
products and specifications or to discontinue any product or service without notice.
Customers should therefore obtain the latest version of relevant information from GSS to verify that the
information is current. Testing and other quality control techniques are utilised to the extent GSS deems
necessary to support its warranty. Specific testing of all parameters of each device is not necessarily
performed unless required by law or regulation. In order to minimise risks associated with customer
applications, the customer must use adequate design and operating safeguards to minimise inherent or
procedural hazards. GSS is not liable for applications assistance or customer product design. The customer is
solely responsible for its selection and use of GSS products. GSS is not liable for such selection or use nor for
use of any circuitry other than circuitry entirely embodied in a GSS product.
GSS products are not intended for use in life support systems, appliances, nuclear systems or systems where
malfunction can reasonably be expected to result in personal injury, death or severe property or
environmental damage. Any use of products by the customer for such purposes is at the customer’s own risk.
GSS does not grant any licence (express or implied) under any patent right, copyright, mask work right or other
intellectual property right of GSS covering or relating to any combination, machine, or process in which its
products or services might be or are used. Any provision or publication of any third party’s products or
services does not constitute GSS’s approval, licence, warranty or endorsement thereof. Any third party trademarks contained in this document belong to the respective third-party owner.
Reproduction of information from GSS datasheets is permissible only if reproduction is without alteration and
is accompanied by all associated copyright, proprietary and other notices (including this notice) and
conditions. GSS is not liable for any unauthorised alteration of such information or for any reliance placed
thereon.
Any representations made, warranties given, and/or liabilities accepted by any person which differ from those
contained in this datasheet or in GSS’s standard terms and conditions of sale, delivery and payment are made,
given and/or accepted at that person’s own risk. GSS is not liable for any such representations, warranties or
liabilities or for any reliance placed thereon by any person.
ADDRESS
Gas Sensing Solutions Ltd.
Grayshill Road
Cumbernauld
G68 9HQ
United Kingdom
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CozIR®-A
Flexible Low Power CO2 Sensor
REVISION HISTORY
DATE
05/03/2020
13/05/2020
10/06/2020
15/01/2021
RELEASE
4.0
4.1
4.2
4.3
01/02/2021 4.4
DESCRIPTION OF CHANGES
First revision
Updated auto-zero language
ABSOLUTE MAXIMUM RATINGS
INTERFACE TIMING – NITROGEN_ZERO and
FRESH_AIR_ZERO
ABSOLUTE MAXIMUM RATINGS
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