1. sports
2. skating
3. figure skating

Gas and Air Sensors
Technical Description
SenseAir ® S8
Miniature CO2 sensor module
PRELIMINARY
Technical Description
SenseAir ® S8
Miniature CO2 sensor module
.
Figure 1a. SenseAir ® S8
Article #400010
Figure 1b. SenseAir ® S8
Article #400011
Warning! ESD
sensitive device!
General
Revision 2.13 of this PRELIMINARY specification is intended to present the
first 2 models of the SenseAir® S8 model family and also discuss with
customers the preferable connection between customer’s system and
SenseAir ® S8 miniature CO2 measurement module.
The SenseAir® S8 models presented in this document are the first ones in the family
of models customized for a variety of sensing, control and alarm applications. The
sensor family is designed to be a miniature OEM module for built-in applications in a
host apparatus, and hence should be optimized for its tasks during a dialog between
SenseAir and the OEM customer. This document can be considered as the starting
point for such a dialog.
Please refer Appendix A for more information on possible options of the model
family. Some of described possible functionality of sensors in the SenseAir ® S8
model family is not implemented yet but it can be implemented on customer’s
request.
I/O notations used in this document, terminal positions and some important
SenseAir® S8 dimensions are described at the next pages.
IMPORTANT NOTICE: Current version of the document represents the series sensor
interfaces and mechanical dimensions. Descriptions of prototypes produced are
collected in Appendix B.
Revision 2.13, 2010-04-14
PRELIMINARY
SenseAir ® S8 – Key technical specification
SenseAir® S8
Item
CO2
Target gas
Measurement
range
Accuracy
Response time
Up to 10000ppm extended range (Note 2)
+-30ppm+-3% of reading
(Notes 3 and 4)
Operating
humidity
0 to 95% RH non condensed
Storage
temperature
-40 to + 70 C
Dimensions
(body)
32.7*19.7*8.3 mm3 for #400010
33.3*19.7*8.3 mm3 for #400011
Weight
TBD
Power supply
5V +-5% unprotected against surges and
reverse connection
Compliance with
Sensor rated for California standard is
planned. Please contact SenseAir for
further information
2 minutes by 90% for diffusion sampling method
model
0 to 50C
Sensor life
Contact SenseAir for other gases
availability
400 to 5000 ppm (Note 1),
Operating
temperature
Power
consumption
Possible functionality of other
members in SenseAir® S8 family
300 mA peak,
30 mA average
Sensors for extended temperature ranges
-40 to +85C are under development
Sensors for extended temperature ranges
-40 to +85C are under development
Low power versions are planned. Contact
SenseAir for details and schedule.
15 years in normal commercial environments
with ABC on (Note 3)
CE conformity declaration not required because SenseAir is going to perform immunity and
it’s not a product directed to end user. Our
emission tests anyway to confirm
customers have to make this declaration for
compliance of the module in immunity and
their entire product.
emission
RoHS directive 2002/95/EG
Other tests / approvals are available on
request, contact SenseAir
Continue on the next page….
Table I. Key technical specification for the SenseAir ® S8
__________________________________________________________________________________________
Note 1: Sensor is designed to measure in the range 0 to 5000 ppm with specified in the table accuracy. Nevertheless exposure
to concentrations below 400 ppm may result in incorrect operation of ABC algorithm and shall be avoided for model with
ABC on.
Note 2: Sensor provides readings via UART in the extended range but the accuracy is degraded compared to specified in the
table one.
Note 3: In normal IAQ applications. Accuracy is defined after minimum 3 weeks of continuous operation. However, some
industrial applications do require maintenance. Please, contact SenseAir for further information!
Note 4: Accuracy is specified over operating temperature range. Specification is referenced to certified calibration mixtures.
Uncertainty of calibration gas mixtures (+-2% currently) is to be added to the specified accuracy for absolute
measurements.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 3 of 27
PRELIMINARY
SenseAir ® S8 – Key technical specification (continuation)
Possible functionality of other
members in SenseAir® S8 family
SenseAir® S8
Item
Serial
communication
UART, Modbus protocol (Note 5)
Direction control pin for direct connection to
RS485 receiver integrated circuit.
FastStream protocol
delivering dedicated measurement data
with dedicated time intervals is under
development
Alarm output,
Open Collector
Normally Conducting after power up,
Non conducting (high level) at > 1000 ppm,
return to conducting (low level) at < 800 ppm
Non Conducting (high level) at error detected
Contact SenseAir for other optional
functionality of OC and threshold
configuration.
PWM output, 1 kHz 0 to 100% duty cycle for 0 to 2000 ppm
Contact SenseAir for other optional
output ranges.
3.3V push-pull CMOS output, unprotected
Forced calibration
Background calibration in fresh air (400 ppm)
by forcing bCal input Low for about 4 sec.
Keeping bCal input low for more than 16 sec
forces sensor to perform zero (nitrogen)
calibration
Table I (continuation). Key technical specification for the SenseAir ® S8
__________________________________________________________________________________________
Note 5: See specification { Modbus on SenseAir(R) S8 rev_P01_1_00.doc preliminary specification}
Absolute maximum ratings
Stress greater than those listed in Table II may cause permanent damage to the device. These ratings
are stress ratings only. Operation of the device at any condition outside those indicated in the
operational section of these specifications is not implied. Exposure to absolute maximum rating for
extended periods may affect device reliability.
Parameter
Minimum
Maximum
Units Notes
Ambient temperature under bias
-40
85
C
Voltage on G+ pin with respect to G0 pin
-0.3
12
V
1, 2
Maximum output current from active output pin
-25
+25
mA
1
Maximum current on input
-5
+5
uA
1
Maximum voltage on UART lines, PWM and bCAL_in
-0.3
DVCC_out+0.5
V
1
Maximum voltage on Alarm_OC
-0.3
12
V
1,3
Table II. Absolute maximum ratings specification for the SenseAir ® S8
__________________________________________________________________________________________
Note 1: Specified parameter relies on specification of subcontractor and is not tested by SenseAir
Note 2: Refer chapter “Terminal Description” for rated voltage information
Note 3: Alarm_OC pin is internally pulled up to G+. External pull up to higher voltage will provide resistive divider powering
sensor via high resistance.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 4 of 27
PRELIMINARY
Assembling into customer’s system (examples)
Conventional through-hole pin header soldering / insert are used to mount SenseAir ® S8
into customer’s system. Either manual or automated wave soldering may be used. Pin assignment is
shown on figure 4 and description of function and electrical properties is given in the table III.
9.3*
8.3 max
10.16
Pin header, 2.54 mm pitch
3.18 ±0.15
19.6 ±0.1
10.7 ±0.2
26.3 ±0.1
13.2 ±0.1
2.54
12.6*
2.97 ±0.15
1.6**
6 ±0.15
29.7 ±0.1
7.6 ±0.15
+0.7
32.2 - 0.2
Article #400010 to customer PCB.
1.6 ±0.16
Figure 2a. Assembling SenseAir ® S8
Sensor
Customer PCB
* For reference only. It depends on pin header type.
** For reference only. It depends on customer PCB thickness.
Figure 2b. Assembling SenseAir ® S8
height.
Article #400010 to customer PCB for the smallest total
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 5 of 27
PRELIMINARY
Sensor
Connector
Adhesive double side tape
Customer PCB or other mounting surface
Figure 2c. Assembling SenseAir ® S8
Article #400011to customer PCB by double side tape.
Clamp
Screw
Sensor
Connector
Customer PCB or other mounting surface
Figure 2d. Assembling SenseAir ® S8
Article #400011 to customer PCB.
NOTE: SenseAir doesn’t offer the clamp part, picture represents assembling idea. Please contact
SenseAir for technical drawings.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 6 of 27
PRELIMINARY
Sample gas diffusion area
Diffusion area
Figure 3a. Diffusion area, SenseAir ® S8
Article #400010.
Diffusion area
Figure 3b. Diffusion area, SenseAir ® S8
Article #400011.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 7 of 27
PRELIMINARY
Pin assignment
Pin 6
Pin 7
Pin 8
Pin 9
G+
G0
Alarm_OC
PWM 1kHz
DVCC_out
UART_RxD
UART_TxD
UART_R/T
bCAL_in
pin 5
Pin 4
Pin 3
Pin 2
Pin 1
Figure 4a. Attachment to customer’s PCB, not in scale, SenseAir ® S8
Article #400010.
Pin 10 is absent and it serves as a key to prevent incorrect assembling into customer’s system.
Red designates difference from the prototype produced.
Pin 1
Pin 2
Pin 3
Pin4
Pin 5
Pin 6
Pin 7
Pin 8
Pin 9
G+
G0
Alarm_OC
PWM 1kHz
DVCC_out
UART_RxD
UART_TxD
UART_R/T
bCAL_in
Figure 4b. Attachment to customer’s PCB, not in scale, SenseAir ® S8
G+
G0
Alarm_OC
PWM 1kHz
Figure 4c. Attachment to customer’s PCB, not in scale, SenseAir ® S8
back view.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Article #400011.
Pin 1
Pin 2
Pin 3
Pin 4
Article #400011,
Page 8 of 27
PRELIMINARY
Terminals description
The table below specifies terminals and I/O options dedicated in SenseAir ® S8 model.
Pin Function
Pin description /
Parameter description
Electrical specification
Power pins
G0
Power supply minus terminal
Sensor’s reference (ground) terminal
G+ referred
to G0
DVCC_out
Power supply plus terminal
Unprotected against reverse
connection!
Absolute max supply voltage (Note 1)
12v survival
Operating voltage range
5VDC+-5%
Output
Output may be used to logical level
converter if master processor runs at 5V
supply voltage.
Induced noise or excessive
current drawn may affect sensor
performance. External series
resistor is strongly
recommended if this pin is used
Series resistance
No internal protection!
Nominal voltage
3.3 VDC
Allowed source current
6 mA max
Voltage precision (Note 1)
+-3% max (+-0.75% typ)
from sensor’s voltage regulator.
Communication pins
UART_TxD
UART_RxD
UART_R/T
UART data transmission line.
Configured as digital output
No internal protection,
Pulled up to DVCC_out at
processor reset
(power up and power down).
Absolute max voltage range(Note 1)
G0 -0.3V to DVCC_out + 0.5V
Internal pull up to DVCC_out resistor
120k
Output low level (Note 1)
0.75 VDC max at 10mA sink
Output high level (Note 1)
2.4 VDC at 2mA source
UART data receive line.
Configured as digital input
No internal protection,
Pulled up to DVCC_out at
processor reset
(power up and power down).
Absolute max voltage range(Note 1)
G0 -0.3V to DVCC_out + 0.5V
Internal pull up to DVCC_out resistor
120k
Input low level (Note 1)
-0.3V to 0.75V
Input high level (Note 1)
2.3V to DVCC_out+0.3V
Direction control line for half duplex
RS485 transceiver like MAX485.
Configured as digital output
Absolute max voltage range(Note 1)
No internal protection,
Pulled down at processor reset
(power up and power down).
Internal pull down to G0 resistor
120k
Output low level (Note 1)
G0 -0.3V to DVCC_out + 0.5V
0.75 VDC max at 10mA sink
Output high level (Note 1)
2.4 VDC at 2mA source
.Table III. I/O notations, description and electrical specification. Please, continue on the next page!
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 9 of 27
PRELIMINARY
Pin Function
Pin description /
Parameter description
Electrical specification
Digital input forcing background
calibration.
Configured as digital input.
No internal protection,
Pulled up to DVCC_out at
processor reset
(power up and power down).
Input / output
bCAL_ in
Pulling input low in more than 2
seconds activates background
calibration procedure. See chapter
“Calibration” for details
PWM 1kHz
Absolute max voltage range(Note 1)
Internal pull up to DVCC_out resistor
G0 -0.3V to DVCC_out + 0.5V
Input low level (Note 1)
-0.3V to 0.75V
Input high level (Note 1)
2.3V to DVCC_out+0.3V
PWM output
Configured as digital output
No internal protection,
Pulled down at processor reset
(power up and power down).
120k
Used for direct reading by customer’s
microcontroller or to provide analog
output. Refer “Use scenario
suggestion” for details and ideas.
Alarm_OC
Duty cycle min
0%, output Low
Duty cycle max
100%, output High
PWM resolution
0.5usec +-4%
PWM period
1 msec +-4%
Absolute max voltage range(Note 1)
Internal pull down do G0 resistor
G0 -0.3V to DVCC_out + 0.5V
Output low level (Note 1)
0.75 VDC max at 10mA sink
Output high level (Note 1)
2.4 VDC at 2mA source
Open Collector output for alarm
indication
No internal protection,
Pulled up to G+ at processor reset
(power up and power down).
Absolute max voltage range(Note 1)
G0 -0.3V to 12V
Internal pull up to G+ resistor
120k
Max sink current (Note 1)
100 mA
Saturation voltage (Note 1)
2.3V to DVCC_out+0.3V
120k
Table III. I/O notations, description and electrical specification (continue, see previous page).
Please, beware of the dark red colored texts that pinpoint important features for the system
integration!
__________________________________________________________________________________________
Note 1: Specified parameter relies on specification of subcontractor and is not tested by SenseAir
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 10 of 27
PRELIMINARY
Use scenario suggestion
The following schematics suggest use scenario of SenseAir ® S8
NOTICE: Drawings represent connections required for coming series produced sensors.
It differs from required connections for prototypes; see Appendix B for prototypes
required connection.
Figure 5. Use SenseAir ® S8 for simple low cost transmitter with optional background calibration
button.
Figure 6. Use SenseAir ® S8 for simple low cost Modbus over RS485 transmitter.
Calibration button is optional.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 11 of 27
PRELIMINARY
Figure 7a. Use SenseAir ® S8 in microprocessor based system, general approach with UART
communication and separate voltage supply to sensor and master microprocessor.
Figure 7b. Use SenseAir ® S8 in microprocessor based system, general approach with UART
communication. Master microprocessor is powered from 5V and voltage translator is required to
for logical levels conversion.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 12 of 27
PRELIMINARY
Figure 8. Use SenseAir ® S8 in microprocessor based system, general approach without UART
communication. Duty cycle of PWM1 can be measured by processor with 1 timer only.
ATTENTION! It’s duty cycle that should be measured to obtain best accuracy of reading. PWM has
worst case +-4% tolerance of the time scale that can result in errors when measuring only pulse
length.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 13 of 27
PRELIMINARY
General mechanical overview
6 ±0.15
+0.7
3.18 ±0.15
1
19.6 ±0.1
9 pins
10.7 ±0.2
2.54
13.2 ±0.2
2.97 ±0.15
26.3 ±0.1
8.3 max
7.60 ±0.15
1.6 ±0.16
32.2 - 0.2
29.7 ±0.1
Article #400010.
Figure 9a. Mechanical drawing SenseAir ® S8
Red designates difference from the prototype produced.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 14 of 27
PRELIMINARY
+0.7
33 - 0.2
26.3 ±0.1
View A
0.651
9.8 ±0.2
+0.7
1.60 ±0.16
32.7 - 0.2
0.3 ±0.15
7.6 ±0.15
8.3 max
0.851 ±0.2
3 ±0.2
4.56 ±0.2
11
19.6 ±0.1
13.20 ±0.2
A
ja by predpochel razmer kak 32.7 -0.2 +0.7 I analogichno s razmerom 33.
Nuzhno uchest’ scoring na prototypah tozhe.
Krome togo, ja by erestavil 33 razmer naverh, imenno na nego ja snachala dumal, chto eto max
gabarit.
Kstati, zdes’ tozhe neploho prostavit’ kontrol’nye razmery, kotorye dolzhna proverjat’ sluzhba kontrolja
kachestva. Obsudi s Jan-Åke I Ulfom!
Figure 9b. Mechanical drawing SenseAir ® S8
.
Article #yyyyyyyyyy.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 15 of 27
Maintenance
The models based on SenseAir ® S8 platform are basically maintenance free in normal environments
thanks to the built-in self-correcting ABC algorithm. Discuss your application with SenseAir in order to
get advice for a proper calibration strategy.
When checking the sensor accuracy, PLEASE NOTE that the sensor accuracy is defined at
continuous operation (at least 3 weeks after installation)!
ABC (Automatic Baseline Correction)
The default sensor OEM unit is maintenance free in normal environments thanks to the built-in selfcorrecting ABC algorithm (Automatic Baseline Correction). This algorithm constantly keeps track of
the sensor’s lowest reading over a 7,5 days interval and slowly corrects for any long-term drift
detected as compared to the expected fresh air value of 400ppm (or 0.04%vol) CO2.
Calibration
Rough handling and transportation might result in a reduction of sensor reading accuracy. With time,
the ABC function will tune the readings back to the correct numbers. The default “tuning speed” is
however limited to about 70 ppm/week. For post calibration convenience, in the event that one cannot
wait for the ABC algorithm to cure any calibration offset, switch inputs may be defined for the operator
or master system to select one out of two prepared calibration codes. One of internal calibration codes
is bCAL (background calibration), in which case it is assumed that the sensor is operating in a fresh
air environment (400 ppm CO2). Another operation code is CAL (zero calibration), in which case the
sensor must be purged by some gas mixture free from CO2 (i.e. Nitrogen or Soda Lime CO2 scrubbed
air). Make sure that the sensor environment is steady and calm!
Both background and zero calibrations are made available for starting by hardware
Input
bCAL_in
Default function
(when closed for minimum 4, max 8 seconds)
bCAL (background calibration) assuming 400 ppm CO2 sensor exposure
bCAL_in
(when closed for minimum 16 seconds)
CAL (zero calibration) assuming 0 ppm CO2 sensor exposure
Table IV. Switch input default configurations for SenseAir ® S8
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 16 of 27
Self-diagnostics
The system contains complete self-diagnostic procedures. A full system test is executed automatically
every time the power is turned on. In addition, constantly during operation, the sensor probes are
checked against failure by checking the valid dynamic measurement ranges. All EEPROM updates,
initiated by the sensor itself, as well as by external connections, are checked by subsequent memory
read back and data comparisons. These different system checks return error bytes to the system
RAM. The full error codes are available from the UART port communication. Out of Range error is the
only bit that is reset automatically after return to normal state. All other error bits have to be reset after
return to normal by UART overwrite, or by power off/on.
Error code and action plan
(error code can be read via one of the communication channels)
Bit #
Error
code
0
Error description
Suggested action
1
Fatal Error
Try to restart sensor by power OFF/ON.
Contact local distributor.
1
2
Reserved
2
4
Algorithm Error.
Indicate wrong configuration.
Try to restart sensor by power OFF/ON.
Check detailed settings and configuration
with software tools.
Contact local distributor.
3
8
Output Error
Detected errors during output signals
calculation and generation.
Check connections and loads of outputs.
Check detailed status of outputs with
software tools.
4
16
Check detailed self-diagnostic status with
software tools. Contact local distributor.
5
32
Self-Diagnostic Error.
May indicate the need of zero
calibration or sensor replacement.
Out Of Range Error
Accompanies most of other errors.
Can also indicate overload or failures
of sensors and inputs.
Resets automatically after source of
error disappearance.
Check connections of temperature and
relative humidity probe (if mounted).
Try sensor in fresh air.
Perform CO2 background calibration.
Check detailed status of measurements
with software tools.
See Note 1!
Check detailed settings and configuration
with software tools.
6
64
Memory Error
Error during memory operations.
7
128
Reserved
Table V. Error codes for SenseAir ® S8
Note 1. Any probe is out of range. Occurs, for instance, during over-exposure of CO2 sensor, in which
case the error code will automatically reset when the measurement values return to normal. Could
also indicate the need of zero point calibration. If the CO2 readings are normal, and still the error code
remains, any other sensor probe mounted (if any) can be defect, or the connection to this probe is
broken.
Please remark: If several errors are detected at the same time the different error code numbers will
be added together into one single error code!
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 17 of 27
WARRANTY and Limitation of Liability
1. SenseAir warrants that for a period of twenty four (24) months following receipt by Buyer
the Product supplied by SenseAir to Buyer will be, under normal use and care, free from
defects in workmanship or material and to be in material conformity with SenseAir's
specifications. Units returned to SenseAir for warranty repairs shall be shipped to SenseAir,
at Buyer’s expense, according to SenseAir's instruction. Within ninety (90) days of the receipt
of product, SenseAir shall replace or repair such units and shall ship them to Buyer’s
designated return destination freight pre paid.
2. Warranty Limitations. This warranty does not extend to any unit that has been
subject to misuse, neglect or accident; that has been damaged by causes external to the
unit; that has been used in violation of SenseAir's instructions; that has been affixed to any
non-standard Accessory attachment; or that has been modified, disassembled, or
reassembled by anyone other than SenseAir.
3. The retailer is not responsible for any consequential loss or damages, which may occur by
reason of purchase and use of this product. The warranty is, in any event, strictly limited to
the replacement/repair of the product
SenseAir AB • Box 96 • SE-820 60 Delsbo • Sweden
Phone: +46-(0)653-71 77 70 • Fax: +46-(0)653-71 77 89
Home page: www.senseair.com • E-mail: senseair@senseair.com
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 18 of 27
Appendix A.
Possible digital I/O configurations
The following pins have hardwired configuration:
Pin Function
Pin description /
Parameter description
Electrical specification
Power pins
G0
Power supply minus terminal
Sensor’s reference (ground) terminal
G+ referred
to G0
DVCC_out
Power supply plus terminal
Unprotected against reverse
connection!
Absolute max supply voltage (Note 1)
12v survival
Operating voltage range
5VDC+-5%
Output
Output may be used to logical level
converter if master processor runs at 5V
supply voltage.
Induced noise or excessive
current drawn may affect sensor
performance. External series
resistor is strongly
recommended if this pin is used
Series resistance
No internal protection!
Nominal voltage
3.3 VDC
Allowed source current
6 mA max
Voltage precision (Note 1)
+-3% max (+-0.75% typ)
from sensor’s voltage regulator.
Communication pins
UART_TxD
UART_RxD
UART_R/T
UART data transmission line.
Configured as digital output
No internal protection,
Pulled up to DVCC_out at
processor reset
(power up and power down).
Absolute max voltage range(Note 1)
G0 -0.3V to DVCC_out + 0.5V
Internal pull up to DVCC_out resistor
120k
Output low level (Note 1)
0.75 VDC max at 10mA sink
Output high level (Note 1)
2.4 VDC at 2mA source
UART data receive line.
Configured as digital input
No internal protection,
Pulled up to DVCC_out at
processor reset
(power up and power down).
Absolute max voltage range(Note 1)
G0 -0.3V to DVCC_out + 0.5V
Internal pull up to DVCC_out resistor
120k
Input low level (Note 1)
-0.3V to 0.75V
Input high level (Note 1)
2.3V to DVCC_out+0.3V
Direction control line for half duplex
RS485 transceiver like MAX485.
Configured as digital output
Absolute max voltage range(Note 1)
No internal protection,
Pulled down at processor reset
(power up and power down).
Internal pull down to G0 resistor
120k
Output low level (Note 1)
Output high level (Note 1)
G0 -0.3V to DVCC_out + 0.5V
0.75 VDC max at 10mA sink
2.4 VDC at 2mA source
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 19 of 27
Alarm_OC
Open Collector output for alarm
indication
No internal protection,
Pulled up to G+ at processor reset
(power up and power down).
Absolute max voltage range(Note 1)
G0 -0.3V to 12V
Internal pull up to G+ resistor
120k
Max sink current (Note 1)
100 mA
Saturation voltage (Note 1)
2.3V to DVCC_out+0.3V
Table VI. I/O notations used in this document for the SenseAir ® S8 model
Other pin’s functionality can be configured in firmware and customized after customer’s wishes and
application ideas. The table VII below lists the possible functions:
Function
Descriptions and ratings
Input / Outputs
There are 4 pins with 3.3V CMOS logical levels that can have
one of the following functions.
Status Output
Digital output, unprotected CMOS.
1. Generates High or Low level if error is discovered during selftest.
Alarm Output
Digital output, unprotected CMOS.
High CO2 alarm at for example 2000 ppm. Active low or active high
level.
Warning Output
Digital output, unprotected CMOS.
High CO2 warning at for example 800 ppm. Active low or active high
level.
Fast PWM1 Output
Digital output, unprotected CMOS.
1. PWM output, 10 (alt. 12 to 16) bit resolution. Period 1 msec
Pulse length proportional to measured CO2 value. May be filtered by
external RC network to provide linear analog output.
Slow PWM2 Output
Digital output, unprotected CMOS.
1. PWM output, 10 (alt. 12 to 16) bit resolution. Period 1004 msec
Pulse length proportional to measured CO2 value.
Zero Calibration
input
Digital switch inputs
Used for zero calibration forcing.
Background
Calibration input
Digital switch inputs
Used for background calibration forcing.
UART_R/T output
Digital output
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 20 of 27
Used to control RS485 transceiver. Future option.
Sleep forcing input
Digital switch inputs
Used to force sensor into sleep low power consumption mode.
Range switch input
Digital switch inputs
Used to force sensor to change output range, for example, from
0..2000 ppm to 0..5000 ppm for given PWM output.
Used to force sensor to change alarm level, for example, from 1000
ppm to 1400 ppm.
Table VII. I/O ideas for the SenseAir ® S8 family sensors
Other use ideas
2 mm pin header
Sensor
Cutout for plastic part of sensor
Customer PCB
Figure ii. Assembling SenseAir ® S8 Article #zzzzzzzzzz
SMD connector) to customer PCB for smallest height.
(400011 without mounted
Diffusion area
Figure 3c. Diffusion area, SenseAir ® S8
Article #zzzzzzzzzzz.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 21 of 27
4.6 ±0.20
View A
26.3 ±0.1
2
6
19.6 ±0.1
13.20 ±0.2
A
+0.7
32.7 - 0.2
0.3 ±0.15
7.6 ±0.15
4.6 ±0.2
8.3 max
1.60 ±0.16
+0.7
33 - 0.2
Figure 9c. Mechanical drawing SenseAir ® S8
Article #zzzzzzzzzzzzzzz.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 22 of 27
Appendix B.
Description of produced prototypes run
Pin assignment
Pin 6
Pin 7
Pin 8
Pin 9
G+
G0
bCAL_ in
DVCC_out
PWM 1kHz
UART_RxD
UART_TxD
UART_R/T
Reserved
Pin 5
Pin 4
Pin 3
Pin 2
Pin 1
Figure 4. Attachment to customer’s PCB, SenseAir ® S8.
Pin 10 is absent and it serves as a key to prevent incorrect assembling into customer’s system.
Dimensions
Figure 9. Mechanical drawing SenseAir ® S8.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 23 of 27
Use scenario suggestion
The following schematics suggest use scenario of SenseAir ® S8 prototypes
NOTICE: Drawings represent connections required by prototype and will be updated for
series products. Pull-up/down resistors are moved to the sensor. Pinout of the sensor is
changed
Figure 5. Use SenseAir ® S8 for simple low cost transmitter.
Figure 6. Use SenseAir ® S8 for simple low cost Modbus over RS485 transmitter.
Calibration button is optional.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 24 of 27
Figure 7a. Use SenseAir ® S8 in microprocessor based system, general approach with UART
communication and separate voltage supply to sensor and master microprocessor.
Figure 7b. Use SenseAir ® S8 in microprocessor based system, general approach with UART
communication. Master microprocessor is powered from 5V and voltage translator is required to
for logical levels conversion.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 25 of 27
Figure 8. Use SenseAir ® S8 in microprocessor based system, general approach without UART
communication. Duty cycle of PWM1 can be measured by processor with 1 timer only.
ATTENTION! It’s duty cycle that should be measured to obtain best accuracy of reading. PWM has
worst case +-4% tolerance of the time scale that can result in errors when measuring only pulse
length.
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 26 of 27
Revision history
Revision
1.00
1.01
1.02
Date
2009-03-30
2009-05-15
2009-07-30
Author
PZ and IU
PZ
PZ and IU
1.03
2009-08-05
PZ and IU
1.04
2009-08-08
1.06
1.07
1.08
2.00
2009-12-19
2009-12-20
2010-01-15
2010-01-17
HM
PZ
IU
PZ
IU
PZ
2.01
2.02
2.04
2.05
and
IB
to
2010-03-02
HM, IU,
PZ
IU, PZ
2.10
2010-03-09
IU, PZ
2.11
2010-03-17
IU, PZ
2.12
2010-04-13
HO
2.13
2010-04-14
IU, PZ
2.15
2010-04-14
IU
Description and Comments
First appearance. Preliminary mechanical design
Use scenario drawings are added
Mechanical drawings are updated. Use scenario drawings
are updated and RS485 transmitter is added.
Deleted PCB’s in first two figures. Added figures 15 and 16
for diffusion areas designation
Corrections and additions after review
Mechanical drawings are updated for variant B.
Review and pin functions correction
Changed filter appearance for variant B
1. Change product name according decision of marketing
department.
2. Keep only one “OBA11” version of optics. Another
optical solution that got the name OBA12 will be
documented separately.
3. Add new default pinout configuration and move most
of other use variants into appendix.
Change template to new SenseAir template, format text,
corrections in writing.
Corrections after product board decisions
Corrections after new decisions on the changed pinout and
one more model introduction. Added Appendix B with
description of next version / production series sensor.
The text and figures are left the same in main text describing
already produced prototypes.
Correction and additions after discussions at product board
and project meetings. Prototype description is moved to the
Appendix B and the description of several article numbers is
added to the main text.
Correction and additions after discussions at product board
and project meetings.
Application examples are updated.
Added electrical spec for Alarm_OC
Maximum supply voltage is changed to 0 to 12V
Synchronization
of
marketing
and
development
specifications. The present specification is a development
one.
Updated pictures according design decisions made for S( 2
variants.
Suggestion to change functionality of the alarm output as
more fitting application examples
Updated pictures
EM_ SenseAir _S8_TechnicalDescription_Rev_2_13
Page 27 of 27