E+E Elektronik EE895 User manual

BA_EE895 // V1.0 // technical data are subject to change
User Manual
EE895
MINIATURE SENSOR MODULE
FOR CO2 , TEMPERATURE AND
BAROMETRIC PRESSURE

E+E Elektronik Ges.m.b.H. doesn‘t accept warranty and liability claims neither upon this publication nor in case of
improper treatment of the described products.
The document may contain technical inaccuracies and typographical errors. The content will be revised on a
regular basis. These changes will be implemented in later versions. The described products can be improved and
changed at any time without prior notice.
© Copyright E+E Elektronik Ges.m.b.H. All rights reserved.
EMC note USA (FCC):
This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part 15
of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when
the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio
frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful
interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful
interference in which case the user will be required to correct the interference at his own expense.
EMC note Canada (ICES-003):
CAN ICES-3 (A) / NMB-3 (A)

CONTENTS
1 Introduction .........................................................................................................................................4
1.1 General..........................................................................................................................................................4
1.2 Explanation of Symbols.................................................................................................................................4
1.2.1 General Safety Instructions..................................................................................................................................4
1.3 Environmental Aspects..................................................................................................................................4
1.4 Product Description .......................................................................................................................................5
1.5 Operating Principle CO2Measurement .........................................................................................................5
2 Handling Instructions .........................................................................................................................5
3 Hardware ..............................................................................................................................................5
3.1 Dimensions in mm (inch)...............................................................................................................................5
3.2 Mounting Recommendation ..........................................................................................................................6
3.2.1 Mounting with Pin Header....................................................................................................................................6
3.2.2 Mounting by Soldering .........................................................................................................................................6
3.3 EE895 Block Diagram ...................................................................................................................................7
3.4 Pin Assignment..............................................................................................................................................7
3.5 Pin Description ..............................................................................................................................................7
3.6 Electrical Characteristics ...............................................................................................................................9
3.7 Typical Applications .....................................................................................................................................10
3.7.1 EE895 Connected to USB Interface ..................................................................................................................10
3.7.2 EE895 in Battery Powered Devices ...................................................................................................................10
3.7.3 EE895 Connected to a KNX Bus ....................................................................................................................... 11
4 Digital Interface ................................................................................................................................. 11
4.1 I2C Interface.................................................................................................................................................11
4.1.1 Modbus Protocol Over I2C Interface................................................................................................................... 11
4.1.2 I2C Simplified Protocol .......................................................................................................................................12
4.2 UART Interface............................................................................................................................................14
4.2.1 Modbus Protocol Over UART Interface .............................................................................................................14
4.3 Modbus Register Map .................................................................................................................................14
4.4 EE895 Commands ......................................................................................................................................15
4.4.1 Information .........................................................................................................................................................15
4.4.2 General Settings ................................................................................................................................................15
4.4.3 CO2Parameter Settings.....................................................................................................................................16
Appendix 1 : Technical Note AN0103..........................................................................18
Appendix 2: Technical Data.........................................................................................22

4User Manual EE895 Miniature Sensor Module for CO2, T and p
1 Introduction
1.1 General
This user manual serves for ensuring proper handling and optimal functioning of the device. It shall
be read before commissioning and it shall be provided to all staff involved in transport, installation,
operation, maintenance and repair.
The user manual may not be used for the purposes of competition without the written consent of E+E
Elektronik®and may not be forwarded to third parties. Copies may be made for internal purposes. All
information, technical data and diagrams included in the manual are based on the information available
at the time of writing.
Intended Use
The EE895 miniature sensor module measures the CO2concentration, the temperature (T) and the
absolute barometric pressure (p). It is intended to be used as sensor module in devices for diverse uses
in non-condensing environments. Applications can be , e.g., in building automation, demand controlled
ventilation and process control.
The sensor module can be mounted using several mounting methods. Please observe chapter 3 for
mounting recommendations and descriptions. The use of the EE895 other than described in this manual
is not recommended.
The manufacturer cannot be held responsible for damages as a result of incorrect handling, installation
and maintenance of the device. Unauthorized modifications of the product lead to loss of all warranty
claims. The device may only be powered with safety extra-low voltage (SELV).
Disclaimer
The manufacturer or his authorized agent can only be held liable in case of willful or gross
negligence. In any case, the scope of liability is limited to the corresponding amount of the order issued
to the manufacturer. The manufacturer assumes no liability for damages incurred due to failure to
comply with the applicable regulations, operating instructions or the operating conditions. Consequential
damages are excluded from the liability.
1.2 Explanation of Symbols
This symbol indicates safety information.
It is essential that all safety information is strictly observed. Failure to comply with this information can
lead to personal injuries or damage to property. E+E Elektronik® assumes no liability if this happens.
This symbol indicates instructions.
The instructions shall be observed in order to reach optimal performance of the device.
This symbol indicates ESD (electrostatic discharge) specific notes.
Non-observance can result in damage to the device.
1.2.1 General Safety Instructions
• Use the EE895 only as intended and observe all technical specs.
• This device is not appropriate for safety, emergency stop or other critical applications where device
malfunction or failure could cause injury to human beings.
1.3 Environmental Aspects
Products from E+E Elektronik®are developed and manufactured observing of all relevant requirements
with respect to environment protection. Please observe local regulations for the device disposal.
The individual components of the device shall be disposed of according to local recycling
regulations. The electronics shall be disposed of correctly as electronics waste.

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User Manual EE895 Miniature Sensor Module for CO2, T and p
1.4 Product Description
Beside CO2concentration up to 10.000 ppm, the EE895 measures temperature (T) and absolute
barometric pressure (p). The active pressure and temperature compensation minimizes the impact of
altitude and ambient conditions on the CO2measured data.
The CO2, T and p measured data is available on I²C or UART digital interfaces. The solder pads, the
plated half-holes and the through-holes allow for various mounting options.
1.5 Operating Principle CO2Measurement
The CO2measurement is based on the dual wavelength Non Dispersive Infra-Red (NDIR) technology
which compensates for ageing effects, is highly insensitive to pollution and offers outstanding long term
stability.
The infrared detector 1 (IR-1) is tuned to 4.2 μm, which is the wavelenght absorbed by CO2, the infrared
detector 2 (IR-2) is tuned to 3.9 μm, which is not affected by any gas. For every single flash of the
infrared lamp (IR-L), the device calculates the CO2concentration from the outputs of both infrared
detectors IR-1 and IR-2. The measuring interval is user selectable (factory default: 15 s).
2 Handling Instructions
EE895 is an ESD sensitive device and must be handled with corresponding precautions. Protect the
sensor outside the EPA (Electrostatic Protected Area) using ESD protective packaging.
The EE895 is packed in stacks of ESD trays with 50 pieces each. The tray dimension is 354.2 x 278.6 x
23.8 mm (13.94 x 10.97 x 0.94 inch).
Operating and storage conditions: -40…60 °C (-40…140 °F)
0…95 % RH (non-condensing)
700...1100 mbar (10.15...15.95 psi)
The EE895 housing and the circuit board shall not be exposed to unneccessary mechanical stress
during installation and operation. The forces exerted shall not exceed 50 N.
The sensor module deploys a fine dust filter for sensing element protection. If the EE895 is deployed in a
device which is designed for harsh environments, the device shall deploy a filter as well.
3 Hardware
3.1 Dimensions in mm (inch)
Fig. 1 Dimensions

6User Manual EE895 Miniature Sensor Module for CO2, T and p
Fig. 2 Recommended PCB footprint
3.2 Mounting Recommendation
The EE895 is not intended for reflow soldering and consequently it does not feature a moisture
sensitivity level rate (MSL). Nevertheless, for storage and handling it shall be regarded as compatible
with MSL 1.
EE895 may only be soldered manually. A max. temperature of 360°C may be applied for max.
10s/solder point.
ESD precautions shall be observed while manually soldering the EE895.
The EE895 can be mounted facing either upwards or downwards.
3.2.1 Mounting with Pin Header
The EE895 module can be mounted onto a pluggable female header or directly onto the electronics
board by using a pin-header with 2.54 mm (0.1 inch) pitch.
The minimum clearance of 2 mm (0.08 inch) shall be strictly observed. This is necessary for free air
flow around the CO2sensing cell and around the T/p sensor.
T/p sensor
T/p sensor
h>2 mm (0.08")
h>2 mm (0.08")
Air inlet through dust filter
towards CO2sensing cell
Pin header
Female header
Pluggable
Single pin header
Pin header
Fig. 3 Mounting with pin header
3.2.2 Mounting by Soldering
The EE895 can be mounted by manually soldering the plated half-holes onto the host board.
T/p sensor
8 mm (0.32")
Air inlet through dust filter
towards CO2sensing cell
Solder
Solder
T/p sensor
Fig. 4 Mounting by soldering

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User Manual EE895 Miniature Sensor Module for CO2, T and p
3.3 EE895 Block Diagram
Fig. 5 Block diagram
3.4 Pin Assignment
Fig. 6 Pin assignment
Pin Name Type Comment
1 VCC_EM Power supply Power supply emitter infra-led lamp (IR-L)
2 VCC_IO Power supply Power supply for the microcontroller
3 EN Input Enable the module. Tie to Vcc_IO for normal operation
4 GND Power supply Ground1)
5 GND Power supply Ground1)
6 RDY Output Data ready (open drain output)
7 ISEL Input Interface selection
8 TX / SCL I/O Transmission line (TX) / Serial Clock (SCL)
9 RX / SDA I/O Receive line (RX) / Serial Data (SDA)
1) pins 4 and 5 shall be connected to the same potential
Tab. 1 Pin assignment
3.5 Pin Description
Pin 1 - VCC_EM
Power supply for the infrared lamp (IR-L). For optimizing of the energy consumption such as in battery-
powered devices, the IR-L can be powered separately.
The IR-L does not have to be powered continuously, as it needs power supply during the measurement
cycle tmeas only, see Figure 6. Between the measurement cycles the current consumption of IR-L is
approx. 0.1 µA.

8User Manual EE895 Miniature Sensor Module for CO2, T and p
Pin 2 - VCC_IO
Power supply for the microcontroller and the digital functional blocks.
Pin 3 – EN (Enable)
For battery-powered devices the user can optimize the energy consumption controlling the status of the
EN pin by an external host controller.
When the EN pin is pulled-down to the logic Low 0 (≤0.4 V), the internal voltage regulator of EE895 is
switched off and the current consumption is typically 1 µA (max 2 µA).
When pulled-up to the logic state High (≥0.9 V), the EE895 operates normally.
If the energy consumption of EE895 is not relevant, the EN pin shall be connected to VCC_IO.
The EN pin may not be left open.
Pin 6 – RDY (Data ready)
During the measurement cycle (tmeas), when CO2, T and p are measured and processed, the pin RDY is
in logic state High. As soon as data is available for read out, the pin RDY goes to logic state Low. The
falling edge at this pin indicates that measured data is available for reading, see Figure 6.
If used, an external pull-up resistor is required. If not used, the RDY pin may be left open.
Fig. 7 Timing details (see chapter 4.4.3: „CO2Parameter Settings“)
Pin 7 – ISEL (Interface selection)
The EE895 features I2C and UART interfaces.
Interface selection:
ISEL logic state EE895 interface
Low (0…0.9 V) I2C
High (2.1…5.5 V) or not connected UART
Tab. 2 Interface selection
Serial interface pins:
Pin 8 – TX_SCL Transmission data / Serial clock
Pin 9 – RX_SDA Receiving data / Serial data
The function of pins 8 and 9 depends on the interface selected with pin 7 ISEL:

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User Manual EE895 Miniature Sensor Module for CO2, T and p
Pin 7 – ISEL connected to ground: EE895 features I2C interface:
Pin Mode Note
8 SCL (serial clock) External pull-up resistor to V+ (bus high voltage level) is required.
9 SDA (serial data) External pull-up resistor to V+ (bus high voltage level) is required.
Tab. 3 Pin assignement I2C interface
Example:
Fig. 8 Example I2C interface
Pin 7 – ISEL connected to VCC or left open: EE895 features UART interface:
Pin Mode Note
8 TX (transmission line) CMOS compatible (VOutLowMax 0.4 V; VOutHighMin 2.6 V)
9 RX (receive line) CMOS compatible (VInputLowMax 0.9 V; VInputHighMin 2.1 V)
Tab. 4 Pin assignement UART interface
Example:
Fig. 9 Example UART interface
3.6 Electrical Characteristics
Signal Unit Min Max Note
VCC_EM mA 95 mA @ 3.3V
61 mA @ 5 V
during IR lamp pulse
only (300 ms)
VCC_IO mA 9 mA @ 3.3 V
9 mA @ 5 V
during CO2measurement (600 ms)
and communication only;
else 200 µA
Clock frequency Hz 500 100000
Pull-up resistor kΩ 4.7 100 Typical 10 KΩ
Tab. 5 Electrical characteristics

10 User Manual EE895 Miniature Sensor Module for CO2, T and p
A DC/DC converter is used to flash the lamp (VCC_EM). Therefore, the supply current is reduced with
higher voltage and vice versa. The microcontroller (VCC_IO) is supplied via a linear reglator, hence the
supply current is constant.
The average current consumption at a sampling interval of 15 s (factory default) is 1.5 mA. For the
maximum values, please compare Tab. 5
3.7 Typical Applications
3.7.1 EE895 Connected to USB Interface
Fig. 10 Example USB Interface
Pin 7 - ISEL is not connected → the EE895 features UART interface.
VCC_EM is connected to the nominal 5 V from USB, the VCC_IO and EN are connected to 3.3 V
voltage regulator.
The host can read the values at any time, pin 6 - RDY is not used.
3.7.2 EE895 in Battery Powered Devices
Fig. 11 Example battery powerd devices
Pin 7 - ISEL is connected to the ground → the EE895 features I2C interface.

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User Manual EE895 Miniature Sensor Module for CO2, T and p
VCC_EM is supplied by a low ESR super-capacitor and VCC_IO is connected to a typical low drop
3.3 V regulator.
The I2C host enables the EE895 with pin 3 - EN.
By checking the status of pin 6 - RDY (pulled up), the host can read the data as soon as available. After
reading the data, EE895 can be disabled with pin 3.
3.7.3 EE895 Connected to a KNX Bus
Fig. 12 Example KNX Bus
Pin 7 - ISEL is connected to the ground → the EE895 features I2C interface.
The VCC_EM and the VCC_IO are connected to the typical 5 V bus voltage.
The I2C host keeps the EE895 enabled with the pin 3 – EN and can read the values at any time,
pin 6 - RDY is not used.
4 Digital Interface
The EE895 features standard I2C and UART interfaces.
The interface selection is made with pin 7 – ISEL, see Tab. 2 on page 8.
On both interfaces, I2C and UART, the data is encapsulated in Modbus Protocol Data Units (Modbus
PDUs).
4.1 I2C Interface
The EE895 supports the standard I²C specification. For detailed information about the I2C interface,
please refer to NXP document „I²C-bus specification and user manual“, Rev. 6, 4 April 2014:
www.nxp.com/docs/en/user-guide/UM10204.pdf
The I2C interface simultaneously supports two protocols on two different slave addresses:
• Modbus over I2C address 0x5F
• I2C simplified address 0x5E
These addresses are fixed, they cannot be changed by the user.
4.1.1 Modbus Protocol Over I2C Interface
I2C slave address: 0x5F

12 User Manual EE895 Miniature Sensor Module for CO2, T and p
The I2C interface encapsulates the data according Modbus PDU packets, including CRC:
SSlave Address W A Request: Modbus PDU + Modbus CRC P
SSlave Address R A Response: Modbus PDU + Modbus CRC P
Every byte of the Modbus PDU and the Modbus CRC must be acknowledged
(according to I2C specification, not shown above).
The EE895 module supports repeated START or STOP conditions between the request packet and the
response packet. If a START condition and an address match are detected, the EE895 will stay active
until a STOP condition is received or an idle timeout of 500 ms occurs. This might increase the power
consumption and self-heating. The I2C master shall ensure that the data is retrieved as soon as possib-
le in case of a repeated START.
The CRC16 shall be calculated including the slave address. For the Modbus register map please refer
to chapter 4.3, page 14. For Modbus specifications, please refer to Appendix 1, page 18.
Example of command reading the temperature (floating point value) T = 27.50 °C from the register 0x3EA:
Request [Hex]: S BE 03 03 EA 00 02 E8 C5 P
START Slave address
7-bit shifted
Function
code
Starting
address Hi
Starting
address Lo
No. of
register Hi
No. of
register Lo CRC STOP
S BE 03 03 EA 00 02 E8 C5 P
Response [Hex]: S BF 03 04 00 00 41 DC 74 3F P
START Slave address
7-bit shifted
Function
code
Byte
count
Register 1
value Hi
Register 1
value Lo
Register 2
value Hi
Register 2
value Lo CRC STOP
S BF 03 04 00 00 41 DC 74 3F P
For decoding of float values stored according standard IEEE754, please refer to Appendix 1, page 18.
Example of Decoding:
Response [Hex]:
Byte 1
(Register 2 - Hi)
Byte 2
(Register 2 – Lo)
Byte 3
(Register 1 - Hi)
Byte 4
(Register 1 - Lo) Decimal value
41 DC 00 00 27.50
Please note: For obtaining the correct value, both registers have to be read within the same reading
cycle. The measured value can change between two Modbus requests, therefore, exponent and
mantissa may get inconsistent.
4.1.2 I2C Simplified Protocol
I2C slave adress: 0x5E
This I²C protocol is intended for I2C master reading the measured values from EE895 in
“EEPROM-like-mode”.
The simplified I2C does not support any error detection (such as CRC) and provides the measured data
in 8 subsequent registers, as 16 bit integers.
Slave address 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07
0x5E CO2
high byte
CO2
low byte
T
high byte
T
low byte
reserved*)
high byte
reserved*)
low byte
p
high byte
p
low byte
*) reserved for future use

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User Manual EE895 Miniature Sensor Module for CO2, T and p
The read pointer is the first register to read. Additional bytes are answered by the EE895 module
with NACK. If more bytes are read than the 8 registers, the EE895 answers with 0xFF
(i.e. the SDA line is not pulled down). If a START condition and an address match are detected, the
EE895 will stay active until a STOP condition is received or an idle timeout of 500 ms occurs.
The measured data is available as a 16 bit integer and is expressed in SI units:
Measurand Register pointer Unit Scale
CO2 average 0x00 ppm 1:1
T 0x02 °C 1:100 *
p 0x06 mbar 1:10 **
* Example: 2575 means 25.75 °C
** Example: 10130 means 1013 mbar
Tab. 6 Data availability from the EE895 Miniature Sensor Module
Example for reading all measurands (7-bit address shifted):
Request [Hex]: S BC 00 P
START Slave address
7-bit shifted
Register
pointer STOP
S BC 00 P
Response [Hex]: S BD 03 B0 0A B7 6 70 P
START Slave address
7-bit shifted
CO2
high byte
CO2
low byte
T
high byte
T
low byte
res.*)
high byte
res.*)
low byte
p
high byte
p
low byte STOP
S BD 03 B0 A0 B7 80 00 26 70 P
*) reserved for future use
Conversion:
Measurand Response [Hex] Response [Dec] Value
CO20x03B0 944 944 ppm
T 0x0AB7 2743 27.43 °C
p 0x2670 9840 984.0 mbar
Tab. 7 Interpretation of data from the response
Example for reading the air pressure value (7-bit address shifted):
Request [Hex]: S BC 06 P
START Slave address
7-bit shifted
Register
pointer STOP
S BC 06 P
Response [Hex]: S BD 26 70 P
START Slave address
7-bit shifted
p
high byte
p
low byte STOP
S BD 26 70 P
Conversion:
Measurand Response [Hex] Response [Dec] Value
p 0x2670 9840 984.0 mbar
Tab. 8 Interpretation of data from the response

14 User Manual EE895 Miniature Sensor Module for CO2, T and p
4.2 UART Interface
4.2.1 Modbus Protocol Over UART Interface
Modbus slave address: 0x5F
The interface settings are: Baud rate 9600, 8 Data, No parity, 1 Stop bit (9600 8 N 1)
The slave address and the interface settings are fixed, they cannot be changed by the user.
The EE895 module shall be addressed according to the specification “Modbus over serial line V1.02”,
see http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf .
Modbus frame description (screenshot taken from the “Modbus over serial line Specification and Imple-
mentation Guide V1.02” mentioned above):
4.3 Modbus Register Map
Following Modbus register map is valid for both, the I2C and the UART interface. The measured data is
saved as 32 bit floating point values (data type FLOAT) and as 16 bit signed integer values (data type
INTEGER), please refer to Tab. 9 and Tab. 10 below:
FLOAT 32 bit
Parameter Unit Register number1) [DEC] Register address2) [HEX]
Read register: function code 0x03
Temperature T ° C 1003 0x3EA
Temperature T ° F 1005 0x3EC
Temperature T K 1009 0x3F0
CO2(average) ppm 1061 0x424
CO2(raw) ppm 1063 0x426
Pressure p mbar 1201 0x4B0
Pressure p psi 1203 0x4B2
1) Register number starts from 1
2) Register address starts from 0
Tab. 9 I2C and UART Modbus register map for 32 bit floating point values

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User Manual EE895 Miniature Sensor Module for CO2, T and p
INTEGER 16 bit
Parameter Unit Scale3) Register number1) [DEC] Register address2) [HEX]
Read register: function code 0x03
Temperature T** ° C 100 4002 0xFA1
Temperature T** ° F 50 4003 0xFA2
Temperature T** K 50 4005 0xFA4
CO2(average) ppm 1 4031 0xFBE
CO2(raw) ppm 1 4032 0xFBF
Pressure p* mbar 10 4101 0x1004
Pressure p* psi 100 4102 0x1005
1) Register number starts from 1
2) Register address starts from 0
3) Examples: For scale 100, the reading of 2550 means a value of 25.5. For scale 50, the reading of 2550 means a value of 51.
Tab. 10 I2C and UART Modbus register map for 16 bit signed integer values
4.4 EE895 Commands
The following commands are available via Modbus over I2C and Modbus over UART.
Please note: I2C simplified does not support Modbus encapsulation. Therefore, no Modbus
communication and no settings are possible.
4.4.1 Information
Function code Register address1) [Hex] Description Note
0x06
0x00 Serial number EE895 serial number, ASCII, 0 terminated
0x08 FW-Version (Major, Minor)
High-Byte= Major Version
Low-Byte = Minor Version
Example:
0x011A = 1.26 [01=1; 1A=26]
0x09 Sensor name 2 ASCII characters for each Register (“EE895”)
String is 0-terminated
1) Register address starts from 0
Tab. 11 Available commands for I2C and UART
Please note: When reading the serial number or the sensor name, it is always necessary to read all 8
registers, even if the desired information requires less.
4.4.2 General Settings
The following functions allow for EE895 settings. These are stored in the RAM, therefore they are volatile.
Measuring mode: continuous or single shot
Function code Register address1) [Hex] Note
0x03 0x1F8
[Bit 0] Default status = 0
0 = continuous. The EE895 measures at the regular interval set with the
command “CO2measuring interval”, see 4.4.3.
1 = single shot. The EE895 measures only with the command
“Measuring trigger”, see below.
[Bit 1..15]
reserved (must be written as 0)
1) Register address starts from 0
Tab. 12 Continuous or single shot measurement

16 User Manual EE895 Miniature Sensor Module for CO2, T and p
Measuring status: indicates when new single shot measurement is possible.
Function code Register address1) [Hex] Note
0x03 0x1F9
[Bit 0]: Data ready. The data are available for read out.
0 = busy, 1 = ready
[Bit 1]: Trigger ready. The EE895 is ready for new measurement cycle.
The minimum time interval between two triggers is 10 s.
0 = trigger not possible
1 = ready for new trigger
[Bit 2..15]
reserved (do not use)
1) Register address starts from 0
Tab. 13 Single shot measurement possible
Measuring trigger: command for the single shot measurement. For accurate measurement results,
there are recommended six single shot measurements under stable temperature conditions.
Function code Register address1) [Hex] Note
0x06 0x1FA
[Bit 0]: Measurement Trigger
0 = don’t care
1 = Start new measurement cycle
[Bit 1..15]
reserved (must be written as 0)
1) Register address starts from 0
Tab. 14 Command single shot measurement
EE895 detailed status
Function code Register address1) [Hex] Note
0x06 0x258
[Bit 0]: CO2measurement too high
[Bit 1]: CO2measurement too low
[Bit 2]: T measurement too high
[Bit 3]: T measurement too low
[Bit 6]: p measurement too high
[Bit 7]: p measurement too low
[Bit 8…15]: reserved (do not use)
1) Register address starts from 0
Tab. 15 Status details
4.4.3 CO2Parameter Settings
The CO2parameter settings are non-volatile since they are stored in the flash memory.
Function code Register address1) [Hex] Description Note
0x06
0x1450 CO2measuring interval s
16 bit integer unsigned
Scale 1:10. Example: 150 = 15 seconds
Range 100…36000
Default 15 s
0x1451 CO2filter coefficient*)
16 bit integer unsigned
Range 1…20
Default: 4
0x1452 CO2customer offset ppm
16 bit integer signed
Range -32786…32785
Default: 0 ppm
1) Register address starts from 0
Tab. 16 CO2parameter settings
*) The EE895 features an exponential moving average filter which to a certain degree suppresses the
influence of short-term CO2variations onto the output CO2data. The filter coefficient is user selectable
and affects the response time of the EE895. A higher filter coefficient leads to smoother output data and
to longer response time, see figure 12. Figure 13 shows the number of samples required to reach 63%
or 90% of a CO2 step as function of the filter coefficient.

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User Manual EE895 Miniature Sensor Module for CO2, T and p
Fig. 13 Step response vs. samples
Fig. 14 Step response vs. filter coefficient

18 User Manual EE895 Miniature Sensor Module for CO2, T and p
APPENDIX 1 : TECHNICAL NOTE AN0103
1 Supported Function Codes ..............................................................................................................19
2 Packet Format for Read Coil Code 0x01 .........................................................................................19
2.1 Example: Reading Status............................................................................................................................19
3 Packet Format for Read Function Codes 0x03 and 0x04 ..............................................................19
3.1 Example: Reading Temperature..................................................................................................................20
4 Packet Format for Write Coil Code 0x05 .........................................................................................20
5 Packet Format For Write Function Code 0x06................................................................................20
6 Packet Format for Write Multiple Function Code 0x10 ..................................................................21
7 Data Encoding of Float Values.........................................................................................................21
7.1 IEEE 754 Format.........................................................................................................................................21
7.2 Modbus Floating Point Format ....................................................................................................................21

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User Manual EE895 Miniature Sensor Module for CO2, T and p
1 Supported Function Codes
Following function codes are supported:
• 0x01 Read Coil Register
• 0x03 Read Holding Registers
• 0x04 Read Input Registers
• 0x05 Write Coil Register
• 0x06 Write Single Register
• 0x10 Write Multiple Registers
The measured values can be read by using 0x03 and 0x04 codes. The register numbers and the cor-
responding physical quantities are listed in the datasheet and in the user manual of the specific E+E
device.
2 Packet Format for Read Coil Code 0x01
Request:
Modbus
Address
Function
Code
Communication Address Qunatity of Coils CRC
HB LB HB LB LB HB
YY 01 YY YY YY YY CC CC
Response from the E+E Modbus device:
Modbus
Address Function Code Byte Count
N * Coil Status CRC
HB LB LB HB
YY 01 YY YY YY CC CC
2.1 Example: Reading Status
This example demonstrates reading the device status from a desired address. The supported addres-
ses can be found in the datasheet and in the user manual of the specific E+E device.
Request:
Modbus
Address
Function
Code
Communication Address Qunatity of Registers CRC
HB LB HB LB LB HB
YY 01 00 XX 00 08 CC CC
Quantity of Coils = 8…1 Byte (8Bit)
Response from the E+E Modbus device:
Modbus
Address
Function
Code
Byte
Count
Coils
Status
CRC
LB HB
YY 01 01 YY CC CC
3 Packet Format for Read Function Codes 0x03 and
0x04
Request:
Modbus
Address
Function
Code
Communication Address Qunatity of Registers CRC
HB LB HB LB LB HB
YY 03, 04 YY YY YY YY CC CC
Response from the E+E Modbus device:
Modbus
Address Function Code Byte Count
N * Register CRC
HB LB LB HB
YY 03, 04 YY YY YY CC CC

20 User Manual EE895 Miniature Sensor Module for CO2, T and p
3.1 Example: Reading Temperature
This example demonstrates reading the temperature (float value) from address 0x3A. A float value
consists of 4 Bytes.
Request:
Modbus
Address
Function
Code
Communication Address Qunatity of Registers CRC
HB LB HB LB LB HB
YY 03 00 3A 00 02 CC CC
Response from the E+E Modbus device:
Modbus
Address
Function
Code
Byte
Count 2 Registers (4 Byte) CRC
LB HB
YY 03 04 YY YY YY YY CC CC
4 Packet Format for Write Coil Code 0x05
Request:
Modbus
Address
Function
Code
Communication Address Register Value CRC
HB LB HB LB LB HB
YY 05 YY YY YY YY CC CC
Response from the E+E Modbus device:
Modbus
Address
Function
Code
Communication Address Register Value CRC
HB LB HB LB LB HB
YY 05 YY YY YY YY CC CC
The supported addresses can be found in the datasheet and in the user manual of the specific E+E
device.
5 Packet Format For Write Function Code 0x06
Request:
Modbus
Address
Function
Code
Communication Address Register Value CRC
HB LB HB LB LB HB
YY 06 YY YY YY YY CC CC
Response from the E+E Modbus device:
Modbus
Address
Function
Code
Communication Address Register Value CRC
HB LB HB LB LB HB
YY 06 YY YY YY YY CC CC