Datasheet SEN5x
Environmental Sensor Node for HVAC and Air Quality Applications
▪
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PM, NOx, VOC, RH & T sensor platform
Fast & easy integration
One driver for up to 8 data signals
Superior sensing accuracy and lifetime
Fully calibrated digital output

Overview
The SEN5x is a unique sensor module family combining the measurement of critical air quality parameters –particulate matter, VOC, NOx, humidity, and temperature – in a single package. The modules are a result of
Sensirion’s extensive experience in environmental sensing and offers best possible performance of eachsensing parameter, a superior lifetime, as well as a compact form factor. The SEN5x sensors provide fully
calibrated outputs with a digital interface. The combination of all measurement parameters in a single device
allows manufacturers of air quality devices to reduce design and integration efforts, shorten development times
and simplify their supply chain. Proprietary algorithms enable straightforward integration into HVAC and air
quality applications allowing resource/time savings and focus on core competencies. The implemented
Sensirion Temperature Acceleration Routine (STAR) engine accelerates the device’s response to ambient
temperature change by a factor of 2-3 to provide better UX and more accurate measurements to end users.

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Air
Flow

RH & T
I2C

VOC & NOx
3V3
Laser

Power
Supply

5V

VDD

Laser
Controller

SDA
MCU

SCL

Amplifier &FilterPhotodiode

Fan

ESD
Protection

GND
Fan
Controller

Figure 1 Functional block diagram of the SEN5x. The RH & T and VOC sensors are only contained in the SEN54 and SEN55, theNOx signal is only contained in the SEN55.

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Content
1 Product Family Overview and Ordering Information

4

2 Environmental Sensor Node Specifications

5

3 Electrical Specifications

11

4 Hardware Interface Specifications

13

5 Functional Overview

14

6 Operation and Communication through the I2C Interface

17

7 Technical Drawings

26

8 Revision History

28

9 Important Notices

29

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1 Product Family Overview and Ordering Information
The SEN5x product family consists of a lineup of sensors with identical dimensions, identical hardware & firmwareinterface, and varying number of sensor outputs. Table 1 gives an overview of all available product variants with theirrespective sensor outputs.
Specifications and commands for sensor inputs/outputs only apply for the given product if the sensor output is part ofthis product.
Products
SEN50-SDN-T

Sensor outputs
Particulate Matter

Description

Article Number
3.000.667

Particulate matter sensor, tray packaging,
45 pcs. per tray
SEN54-SDN-T

Particulate Matter
Relative Humidity
Temperature
VOC Index

Environmental sensor node, tray packaging,
45 pcs. per tray

3.000.535

SEN55-SDN-T

Particulate Matter
Relative Humidity
Temperature
VOC Index
NOx Index

Environmental sensor node, tray packaging,
45 pcs. per tray

3.000.593

Table 1: Sensor module specifications.

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2 Environmental Sensor Node Specifications
Default conditions of standard Measurement-Mode (6.1.1), 25 °C and 5 V supply voltage apply to values in the tablebelow, unless otherwise stated.
2.1 Sensor Module Specifications
Parameter
Sampling interval

Conditions-

Lifetime1
Acoustic emission level
Long term acoustic emission level drift
Weight

24 h/day operation
0.2 m
0.2 m
-

Value
1  0.03
> 10
24
+0.5
36.4  10%

Units
s
years
dB(A)
dB(A) / yearg

Table 2: Sensor module specifications.

1 Lifetime is based on mean-time-to-failure (MTTF) calculation. Lifetime might vary depending on different operating conditions.

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2.2 Particulate Matter Specifications
Parameter
Mass concentration specified range
Mass concentration size range

Conditions
PM1.0
PM2.5
PM4
PM10
0 to 100 μg/m3

Value
0 to 1’000
0.3 to 1.0
0.3 to 2.5
0.3 to 4.0
0.3 to 10.0

Units
μg/m3
μm
μm
μm
μm

100 to 1000 μg/m3

5 μg/m3 AND 5 % m.v.
% m.v.
10

0 to 100 μg/m3

25

μg/m3

100 to 1000 μg/m3

25% m.v.

Maximum long-term mass concentration precision
limit drift

0 to 100 μg/m3

1.25

μg/m3 / year

100 to 1000 μg/m3

Typical start-up time6

numberconcentration% m.v. / year
1.25
8
s
16
s
30
s
Calibrated to TSI DustTrak™
DRX 8533 Ambient Mode% m.v. / °C
0.5

Mass concentration precision2,3 for PM1 and PM2.54
Mass concentration precision2,3 for PM4, PM105

Sensor output characteristics
Additional T-dependent mass precision limit drift3
Laser wavelength(DIN EN 60825-1 Class 1)

200 – 3000 #/cm3
100 – 200 #/cm3
50 – 100 #/cm3
PM2.5 mass concentration
temperature
difference to 25°C
typ.

typ.

660

nm

Table 3: Particulate matter sensor specifications. Default conditions of 252 °C, 5010% relative humidity and 5 V supply voltage
apply unless otherwise stated. ‘max.’ means ‘maximum’, ‘typ.’ means ‘typical’, ‘% m.v.’ means ‘% of measured value’.

2 Also referred to as “between-parts variation” or “device-to-device variation”.
3 For further details, please refer to the document “Sensirion Particulate Matter Sensor Specification Statement”.
4 Verification Aerosol for PM2.5 is a 3% atomized KCl solution. Deviation to reference instrument is verified in end-tests for every sensor after calibration.
5 PM4 and PM10 output values are calculated based on distribution profile of all measured particles.
6 Time after starting Measurement-Mode, until a stable measurement is obtained.

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2.3 Temperature and Humidity Specifications
Parameter
Compensated outputs8

Conditions-

Value 7
Temperature andRelative Humidity

Typical accuracy temperature@ 15-30 °C, 50 %RH

Max. accuracy temperature
Repeatability temperature
Response time temperature9@ 15-30 °C, 50 %RH@ 25 °C, 50 %RH

0.45
±0.7
0.1
< 60

Typical accuracy relative humidity@ 25 °C, 30-70 %RH

Max. accuracy relative humidity
Repeatability relative humidity@ 25 °C, 30-70 %RH@ 25 °C, 50 %RH

Response time relative humidity 10@ 25 °C, 50 %RH,  63%@ 25 °C, 50 %RH,  63%

4.5
±6
1
< 20

Units
°C
%RH
°C
°C
°C
s
%RH
%RH
%RH
s

Table 4: Temperature and humidity specifications.

7 For the definition of the typical and max. accuracy tolerance, please refer to the document “Sensirion Humidity Sensor Specification Statement”.
8 Self-heating of the module is compensated according to the application note “Temperature Acceleration and Compensation Instructions for SEN5x”.
9 For a step from 15°C to 25°C

10 For a step from 75%RH to 25%RH

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2.4 Gas Specifications
Parameter
Output signals
Device-to-device
variation

ValuesMin.
11–Comments
VOC Index
NOx Index
VOC Index12

Typ.11
–
–
<±15

Max.
500
500
–

Changing concentration
63
from 5 to 10 ppm of ethanol, at 
90
sampling interval of 1 s
Time until reliably detecting events13

–

<10

–

Units
VOC Index points
NOx Index points
VOC Index pointsor% VOC Index m.v.
(the larger)
NOx Index pointsor% NOx Index m.v.
(the larger)
VOC Index pointsor% VOC Index m.v.
(the larger)
NOx Index pointsor% NOx Index m.v.
(the larger)
s

–

<30

–

s

–

<60

–

s

Time until specifications in this table
are met

VOC Index <1
NOx Index <6

–
–

h
h

<±15
NOx Index12

–

<±50

–

<±50
Repeatability

VOC Index12

–

<±5

–

<±5
NOx Index12

–

<±10

–

<±10
Response time

Switch-on behavior

Table 5: Gas sensing specifications at 25 °C and 50 % RH in zero air (considered as clean air for indoor air quality applications). Allconcentrations refer to ethanol as test gas.

11 95 % of the sensors will be within the typical tolerance corresponding to 2σ assuming a normal distribution for ≥100 sensors.
12 Evaluated using the calibration and test sequence according to the application note SGP40 – Testing Guide.
13 Signal change during 60-s event of 5000 to 10000 ppb of ethanol or of 100 to 300 ppb of NO

2 is three times larger than raw signals drift, without this event during

the same duration.

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2.5 Recommended and Absolute Maximum/Minimum Operating and Storage Conditions
The SEN5x contains different sensing components with different recommended operating and storage ranges. To ensure
an optimal performance of the SEN5x, the “SEN5x Handling Instructions” as well as the “SEN5x Mechanical Assemblyand Design-in Guidelines” need to be followed.

2.5.1 SEN54 and SEN55
Table 6 and Figure 2 show the recommended operating and storage conditions in which all the sensing components of
the SEN54 and SEN55 show best performance, as well as absolute maximum/minimum conditions which must not be
exceeded. Gas sensing specifications are guaranteed only when the SEN54 and SEN55 are operated and stored under
the recommended conditions given in Table 6.
Exposure to conditions outside the recommended range may temporarily reduce sensor performance (reversible RH
drift, reduced RH, T, gas, PM accuracy). Exposure to conditions outside absolute maximum/minimum range may leadto permanently reduced sensor performance (gas sensitivity drift) or cause permanent damage to the device.
The sensor must not be exposed towards condensing conditions at any time.
Recommended

Absolute Maximum/Minimum

Min.

Max.

Min.

Max.

Temperature

10

40

-10

50

Relative humidity

20

80

0

90 (non-condensing) % RH

Temperature

10

30

-40

70

Relative Humidity

20

60

0

80 (non-condensing) % RH

Condition

Parameter

Operating conditions

Storage conditions

Unit

°C

°C

Table 6 Recommended and absolute maximum/minimum operating and storage conditions for SEN54 and SEN55.

Storage
100

80

80

Relative humidity / %Relative humidity / %Operating
100

60
40
20

60
40
20

0
-40

-20

0

20

40

60

80

0
-40

Temperature / °C

-20

0

20

40

60

80

Temperature / °C
Recommended range

Absolute maximum/minimum range

Figure 2 Recommended and absolute maximum/minimum operating and storage conditions for SEN54 and SEN55.

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2.5.2 SEN50
Table 7 and Figure 3 show the recommended operating and storage conditions in which all the sensing components of
the SEN50 shows the best performance, as well as absolute maximum/minimum conditions which must not be exceeded.
Exposure to conditions outside the recommended range may temporarily reduce sensor performance (PM accuracy).
Exposure to conditions outside absolute maximum/minimum range may lead to permanently reduced sensor
performance (gas sensitivity drift) or cause permanent damage to the device.
The sensor must not be exposed towards condensing conditions at any time.
Recommended

Absolute Maximum/Minimum

Min.

Max.

Min.

Max.

Temperature

10

40

-10

60

Relative humidity

20

80

0

95 (non-condensing) % RH

Temperature

10

30

-40

70

Relative Humidity

20

60

0

95 (non-condensing) % RH

Condition

Parameter

Operating conditions

Storage conditions

Unit

°C

°C

Table 7 Recommended and absolute maximum/minimum operating and storage conditions for SEN50.

Storage
100

80

80

Relative humidity / %Relative humidity / %Operating
100

60
40
20
0

60
40
20

-40

-20

0

20

40

60

80

0

-40

Temperature / °C

-20

0

20

40

60

80

Temperature / °C
Recommended range

Absolute maximum/minimum range

Figure 3 Recommended and absolute maximum/minimum operating and storage conditions for SEN50.

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3 Electrical Specifications
3.1 Electrical Characteristics
Parameter
Supply voltage
Sensor startup time (Time after
power-on until I2C
communication can be started)

Conditions-

Idle Mode (first 10 seconds)

Idle Mode (after first 10 seconds)

Average supply current

RHT/Gas-only Measurement Mode
Measurement-Mode (first 60 seconds)

Measurement-Mode (after first 60
seconds)
Peak supply current
Input high level voltage (VIH)
Input low level voltage (VIL)
Output low level voltage (VOL)

SEN55
SEN54
SEN50
SEN55
SEN54
SEN50
SEN55
SEN54
SEN55
SEN54
SEN50
SEN55
SEN54
SEN50

Measurement mode (pulse width of 16µs)
Sink current <6mA

Min
4.5

Typ
5.0

Max
5.5

Unit
V

-

-

50

ms

2.31
0
0

3.8
0.7
0.7
2.6
0.7
0.7
6.8
6.5
70
70
70
63
63
63
100
0

4.2
1
1
3
1
1
8
7.7
100
100
100
80
80
80
110
5.5
0.99
0.4

mA

mA
V

Table 8 Electrical specifications at 25°C.

3.2 Absolute Maximum Ratings
Stress levels beyond those listed in Table 9 may cause permanent damage to the device. These are stress ratings only
and functional operation of the device at these conditions cannot be guaranteed. Exposure to the absolute maximum
rating conditions for extended periods may affect the reliability of the device.
Parameter
Supply voltage VDDInterface Select SEL
I/O pins (RX/SDA, TX/SCL)
Max. current on any I/O pin
Operating temperature range
Operating humidity range
Storage temperature range (short-term, e.g. transport)
Storage humidity range (short-term, e.g. transport)

Min
-0.3
-0.3
-0.3
-16

Max
5.5
5.5
5.5
16
see Table 6
see Table 6
see Table 6
see Table 6

Unit
V
mA

Table 9: Absolute minimum and maximum ratings.

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3.3 ESD / EMC Ratings
Immunity
Description
Electro Static Discharge
Power-Frequency Magnetic Field
Radio-Frequency EM-Field AM-modulatedRadio-Frequency EM-Field AM-modulatedStandard
IEC 61000-4-2
IEC 61000-4-8
IEC 61000-4-3
IEC 61000-4-3

Rating±4 kV contact, ±8 kV air
30A/m, 50Hz and 60Hz
80MHz - 1000MHz, 3V/m, 80% AM @1kHz
1.4GHz – 6GHz, 3V/m, 80% AM @1kHz

Standard
IEC/CISPR 16
IEC/CISPR 16

Rating40dB(µV/m) QP @3m
47dB(µV/m) QP @3m

Emission
Description
Emission in SAC for 30MHz to 230MHz
Emission in SAC for 230MHz to 1000MHz

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4 Hardware Interface Specifications
The sensor is equipped with a serial communication interface. The interface connector is located at the side of the sensor
adjacent to the air outlet. The used connector is ACES 51451-0060N-001 on the sensor’s side, while the corresponding
plug is ACES 51452-006H0H0-001. At the time of writing JST GHR-06V-S is compatible and can be used as well. In
Table 11, a description of the pin layout is given.
Part

Connector

Sensorside

ACES 51451-0060N-001

Cable side Compatible with ACES 51452-006H0H0-001 (e.g.,
JST GHR-06V-S)
Table 10: SEN5x connector
Pin

Name

Description

Comments

1

VDD

Supply voltage

5V ± 10%2

GND

Ground3

SDA

Serial data input / output

LVTTL 3.3V
compatible

4

SCL

Serial clock input

LVTTL 3.3V
compatible

5

SEL

Interface select

6

NC

Do not connect

Connect to
GND

Figure 4 Pin layout. The communication interface
connector (ACES 51451-0060N-001) is located at the sideof the sensor adjacent to the air outlet.

Table 11: SEN5x pin assignment.

Note, that there is an internal electrical connection between GND pin (2) and metal shielding. Keep this metal shielding
electrically floating to avoid any unintended currents through this internal connection. If this is not an option, proper
external potential equalization between GND pin and any potential connected to the shielding is mandatory. Any current
though the connection between GND and metal shielding may damage the product and poses a safety risk throughoverheating.

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5 Functional Overview
5.1 Operating Modes

Start
RHT/Gas-Only
Measurement

Start
Measurement

Figure 5 SEN5x operating modes. The RHT/Gas-Only Measurement Mode is applicable for SEN55 and SEN54 only. The directswitch between Measurement and RHT/Gas-Only Measurement mode is available only for firmware version v2 and newer.

Idle





The module is in Idle Mode after power on or reset.
Most of the internal electronics switched off /reduced power consumption.
Fan and laser are switched off.
The module is ready to receive and process any command.

MeasurementAll electronics switched on / max. power consumption.
The measurement is running, and the module is continuously processing measurement data.
New readings are available every second.

RHT/Gas-Only Measurement






The RHT/Gas-Only Measurement mode can be entered from Idle and the Measurement modes. The directswitch between Measurement and RHT/Gas-Only Measurement mode is available only for firmware version v2
and newer.
Fan and laser are switched off for reduced power consumption.
RHT and gas sensor are switched on. RHT and gas measurement is running, and the module is continuously
processing measurement data.
New readings are available every second.
The PM output is 0xFFFF

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5.2 Fan Auto Cleaning
When the module is in Measurement-Mode an automatic fan-cleaning procedure will be triggered periodically following
a defined cleaning interval. This will accelerate the fan to maximum speed for 10 seconds to blow out the accumulated
dust inside the fan.







Measurement values are not updated while the fan-cleaning is running.
The cleaning interval is set to 604’800 seconds (i.e., 168 hours or 1 week) with a tolerance of 3%.
The interval can be configured using the Set Automatic Cleaning Interval command.
Set the interval to 0 to disable the automatic cleaning.
A sensor reset, resets the cleaning interval to its default value
If the sensor is switched off, the time counter is reset to 0. Make sure to trigger a cleaning cycle at least every
week if the sensor is switched off and on periodically (e.g., once per day).
The cleaning procedure can also be started manually with the Start Cleaning command.



5.3 Temperature compensation
By default, the temperature and humidity outputs from the sensor are compensated for the modules self-heating. If themodule is designed into a device, the temperature compensation might need to be adapted to incorporate the change inthermal coupling and self-heating of other device components.
A guide to achieve optimal performance, including references to mechanical design-in examples can be found in the app
note “Temperature Acceleration and Compensation Instructions for SEN5x” at www.sensirion.com.
5.4 Device Status Register
The Device Status Register is a 32-bit register that contains information about the internal state of the module.
31

30

29

28

27

26

25

24

23

22

21

20

Warning
res.

res.

res.

res.

res.

res.

res.

res.

15

14

13

12

11

10

9

8

res.

Note:

res.

res.

res.

res.

res.

res.

res.

res.

SPEED

19

18

17

16

Info
res.

FAN

res.

res.

res.

3

2

1

0

res.

res.

res.

res.

7

6

5

4

Error

Error

Error

Error

GAS
SENSOR

RHT

LASER

FAN

All “res.” bits are reserved for internal use or future versions. These bits can be both 0 and 1 and should therefore
be ignored.

Bit 21 SPEED: Fan speed out of range
0: Fan speed is ok.
1: Fan speed is too high or too low.
During the first 3 seconds after starting the measurement (fan start-up) the fan speed is not checked.

The fan speed is also not checked during the auto cleaning procedure.



Apart from the two exceptions mentioned above, the fan speed is checked once per second in themeasurement mode. If it is out of range twice in succession, the SPEED-bit is set.



At very high or low ambient temperatures, the fan may take longer to reach its target speed after start-up. In
this case, the bit will be set. As soon as the target speed is reached, this bit is cleared automatically.



If this bit is constantly set, this indicates a problem with the power supply or that the fan is no longer working
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Bit 19 FAN: Fan cleaning active
0: Fan is running normal.
1: Active during the automatic cleaning procedure of the fan
Bit 7 GAS SENSOR: Gas sensor error (VOC & NOx)
0: Gas sensor is running normal.
1: Gas sensor error
Bit 6 RHT: RHT communication error
0: RHT sensor is running normal.
1: Error in internal communication with the RHT sensor
Bit 5 LASER: Laser failure
0: Laser current is ok.
1: Laser is switched on and current is out of range.
The laser current is checked once per second in the measurement mode. If it is out of range, the LASER-bit
is set.



If the laser current is back within limits, this bit will be not cleared automatically.



A laser failure can occur at very high temperatures outside of specifications or when the laser module isdefective.

Bit 4 FAN: Fan failure, fan is mechanically blocked or broken.
0: Fan works as expected.
1: Fan is switched on, but the measured fan speed is 0 RPM.


The fan is checked once per second in the measurement mode. If 0 RPM is measured twice in succession,
the FAN bit is set.



The FAN-bit will not be cleared automatically.



A fan failure can occur if the fan is mechanically blocked or broken.

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6 Operation and Communication through the I2C Interface
Usage:
 I2C address:
0x69
 Max. speed:
standard mode, 100 kbit/s
 Clock stretching: not used
Both SCL and SDA lines are open drain I/Os. They should
be connected to external pull-up resistors (e.g. Rp = 10kΩ). Important notice: in order to correctly select I2C asinterface, the interface select (SEL) pin must be pulled to
GND before or at the same time the sensor is powered up.
Figure 6: Typical I2C application circuit.

To avoid electromagnetic interference and crosstalk, use as short as possible electronic connections (< 10 cm) and/or
well shielded connection cables.
For detailed information on the I2C protocol, refer to NXP I2C-bus specification14.
Checksum Calculation
The Read and Write Commands transmit the data in 2-byte packets, followed by an 8-bit checksum. The checksum is
calculated as follows:
Property
Name
Protected Data
Width
Polynomial
Initialization
Reflect Input
Reflect Output
Final XORExample

Value
CRC-8
read and/or write data
8 bit
0x31 (x^8 + x^5 + x^4 + 1)
0xFF
false
false
0x00
CRC(0xBEEF) = 0x92

uint8_t CalcCrc(uint8_t data[2]) {uint8_t crc = 0xFF;
for(int i = 0; i < 2; i++) {crc ^= data[i];for(uint8_t bit = 8; bit > 0; --bit) {if(crc & 0x80) {crc = (crc << 1) ^ 0x31u;} else {crc = (crc << 1);}}}
return crc;}

Please note that the checksums are used only for the 2-byte data packets. The command code itself already contains a
3-bit CRC and therefore no checksum must be appended to it.

14 http://www.nxp.com/documents/user_manual/UM10204.pdf

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6.1 I2C Commands
The following table shows an overview of the available I2C commands.
Address
Pointer
0x00210x00370x01040x02020x03C40x60B20x60C6
0x60D00x60E10x60F70x61810x56070x80040xD0140xD033
0xD100
0xD206
0xD2100xD304

Command Name

Communication

Start Measurement
Write Data
Start Measurement inWrite Data
RHT/Gas-Only Measurement Mode
Stop Measurement
Write Data
Read Data-Ready Flag
Read/ Write Data
Read Measured Values
Read/ Write Data
Read/ Write Temperature
Read/ Write Data and Parameters
Compensation Parameters
Read/ Write Warm Start
Read/ Write Data and Parameters
Parameters
Read/Write VOC Algorithm Tuning Read/ Write Data and Parameters
Parameters
Read/Write NOx Algorithm Tuning Read/ Write Data and Parameters
Parameters
Read/Write RH/T Acceleration
Read/ Write Data and Parameters
Mode
Read/Write VOC Algorithm State
Read/ Write Data and Parameters
Start Fan Cleaning
Write Data
Read/Write Auto Cleaning Interval Read/ Write Data and Parameters
Read Product Name
Read/ Write Data
Read Serial Number
Read/ Write Data
Read Firmware Version
Read/ Write Data
Read Device Status
Read/ Write Data
Clear Device Status
Write Data
Reset
Write Data

Command execution time
< 50 ms< 50 ms< 200 ms
< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 20 ms< 100 ms

Table 12: Reference table for I2C commands.

Please note that all commands are volatile.
6.1.1 Start Measurement (0x0021)
Starts the measurement. After power up, the module is in Idle-Mode. Before any measurement values can be read, theMeasurement-Mode needs to be started using this command.
6.1.2 Start Measurement in RHT/Gas-Only Measurement Mode (0x0037)
Starts a continuous measurement without PM. Only humidity, temperature, VOC, and NOx are available in this mode.
Laser and fan are switched off to keep power consumption low.
6.1.3 Stop Measurement (0x0104)
Stops the measurement. Use this command to return to the initial state (Idle-Mode).
6.1.4 Read Data-Ready Flag (0x0202)
This command can be used for polling to find out when new measurements are available.

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Read/Write Data:

Byte #
0
1

Description
unused, always 0x00
Data-Ready Flag
0x00: no new measurements available
0x01: new measurements ready to read
Checksum for bytes 0, 1

2

6.1.5 Read Measured Values (0x03C4)
Reads the measured values from the sensor module and resets the “Data-Ready Flag”. If the sensor module is in
Measurement-Mode, an updated measurement value is provided every second and the “Data-Ready Flag” is set. If no
synchronized readout is desired, the “Data-Ready Flag” can be ignored. The command “Read Measured Values” always
returns the latest measured values. After sending the “Read Measured Values” command, a wait time of 10 ms is needed
so that the sensor internally can fill the data buffers. After 20 ms, the read data header can be sent to read out the sensor
data. In RHT/Gas-Only Measurement Mode, the PM output is 0xFFFF. If any value is unknown, 0xFFFF is returned.
Command
0x03C4Returned data
PM Mass concentration, Relative humidity, Temperature, VOC Index, NOx Index

Read/Write Data:

Byte #
0..1

Datatype
big-endian, uint16

2

Checksum for bytes 0, 1

3..4

big-endian, uint16

5

Checksum for bytes 3, 4

6..7

big-endian, uint16

8

Checksum for bytes 6, 7

9..10

big-endian, uint16

11

Checksum for bytes 9, 10

12..13big-endian, int16

14

Checksum for bytes 12, 13

15..16big-endian, int16

17

Checksum for bytes 15, 16

18..19big-endian, int16

20

Checksum for bytes 18, 19

21..22

big-endian, int16

23

Checksum for bytes 21, 22

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Scale factor
10

Description
Mass Concentration PM1.0 [µg/m³]

10Mass Concentration PM2.5 [µg/m³]

10Mass Concentration PM4.0 [µg/m³]

10Mass Concentration PM10 [µg/m³]

100Compensated Ambient Humidity [%RH]200

Compensated Ambient Temperature [°C]10

VOC Index

10

NOx Index

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6.1.6 Read/ Write Temperature Compensation Parameters (0x60B2)
These commands allow to compensate temperature effects of the design-in at customer side by applying a custom
temperature offset to the ambient temperature. The compensated ambient temperature is calculated as follows:
T_Ambient_Compensated = T_Ambient + (slope*T_Ambient) + offset
Where slope and offset are the values set with this command, smoothed with the specified time constant. The time
constant is how fast the slope and offset are applied. After the speciﬁed value in seconds, 63% of the new slope
and offset are applied.
More details about the tuning of these parameters are included in the application note “Temperature Acceleration andCompensation Instructions for SEN5x”.
All temperatures (T_Ambient_Compensated,T_Ambient and offset) are represented in °C.
Read/Write Data and Parameters:

Byte #
0..1

Datatype
big-endian, int16

2

Checksum for bytes 0, 1

3..4

big-endian, int16

5

Checksum for bytes 3, 4

6..7

big-endian, uint16

8

Checksum for bytes 6, 7

Scale factor
200

Description
Temperature offset [°C] (default value: 0)

10000

Normalized temperature offset slope (default value: 0)1Time constant in seconds (default value: 0)

6.1.7 Read/ Write Warm Start Parameter (0x60C6)
The temperature compensation algorithm is optimized for a cold start by default, i.e., it is assumed that the "Start
Measurement" commands are called on a device not yet warmed up by previous measurements. If the measurement isstarted on a device that is already warmed up, this parameter can be used to improve the initial accuracy of theambient temperature output. This parameter can be gotten and set in any state of the device, but it is applied only thenext time starting a measurement, i.e., when sending a "Start Measurement" command. So, the parameter needs tobe written before a warm-start measurement is started.
Read/Write Data and Parameters:

Byte #
0..1

2

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Datatype
big-endian, uint16

Scale factor
1

Description
Warm start behavior as a value in the range from0 (cold start, default value) to 65535 (warm start).
(default value: 0)

Checksum for bytes 0, 1

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6.1.8 Read/ Write VOC Algorithm Tuning Parameters (0x60D0)
The VOC algorithm can be customized by tuning 6 different parameters. More details on the tuning instructions areprovided in the application note “Engineering Guidelines for SEN5x”. Note that this command is available only in idle
mode. In measure mode, this command has no effect. In addition, it has no effect if at least one parameter is outside
the speciﬁed range.
Read/Write Data and Parameters:

Byte #

Datatype

0..1

big-endian, int16

2

Checksum for bytes 0, 1

3..4

big-endian, int16

5

Checksum for bytes 3, 4

6..7

big-endian, int16

8

Checksum for bytes 6, 7

9..10

big-endian, int16

11

Checksum for bytes 9, 10

12..13big-endian, int16

14

Checksum for bytes 12, 13

15..16big-endian, int16

17

Checksum for bytes 15, 16

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Scale
factor
1

Description
Index Offset
VOC index representing typical (average) conditions. Allowed
values are in range 1..250. The default value is 100.

1

Learning Time Offset Hours
Time constant to estimate the VOC algorithm offset from thehistory in hours. Past events will be forgotten after about twice thelearning time. Allowed values are in range 1..1000. The default
value is 12 hours.

1

Learning Time Gain Hours
Time constant to estimate the VOC algorithm gain from the history
in hours. Past events will be forgotten after about twice thelearning time. Allowed values are in range 1..1000. The default
value is 12 hours.

1

Gating Max Duration Minutes
Maximum duration of gating in minutes (freeze of estimator duringhigh VOC index signal). Zero disables the gating. Allowed values
are in range 0..3000. The default value is 180 minutes.

1

Std Initial
Initial estimate for standard deviation. Lower value boosts events
during initial learning period, but may result in larger device-todevice variations. Allowed values are in range 10..5000. The
default value is 50.

1

Gain Factor
Gain factor to amplify or to attenuate the VOC index output.
Allowed values are in range 1..1000. The default value is 230.

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6.1.9 Read/ Write NOx Algorithm Tuning Parameters (0x60E1)
The NOx algorithm can be customized by tuning 6 different parameters. More details on the tuning instructions areprovided in the application note “Engineering Guidelines for SEN5x”. This command is available only in idle mode. In
measure mode, this command has no effect. In addition, it has no effect if at least one parameter is outside thespeciﬁed range.
Read/Write Data and Parameters:

Byte #
0..1

Datatype
big-endian, int16

Scale factor
1

Description
Index Offset
NOx index representing typical (average) conditions. Allowed
values are in range 1..250. The default value is 1.

1

Learning Time Offset Hours
Time constant to estimate the NOx algorithm offset from thehistory in hours. Past events will be forgotten after about twice thelearning time. Allowed values are in range 1..1000. The default
value is 12 hours.

1

Learning Time Gain Hours
The time constant to estimate the NOx algorithm gain from thehistory has no impact for NOx. This parameter is still in place forconsistency reasons with the VOC tuning parameters command.
This parameter must always be set to 12 hours.

1

Gating Max Duration Minutes
Maximum duration of gating in minutes (freeze of estimator duringhigh NOx index signal). Set to zero to disable the gating. Allowed
values are in range 0..3000. The default value is 720 minutes.

2

Checksum for bytes 0, 1

3..4

big-endian, int16

5

Checksum for bytes 3, 4

6..7

big-endian, int16

8

Checksum for bytes 6, 7

9..10

big-endian, int16

11

Checksum for bytes 9, 10

12..13big-endian, int16

1

Std Initial
The initial estimate for standard deviation parameter has no
impact for NOx. This parameter is still in place for consistency
reasons with the VOC tuning parameters command. Thisparameter must always be set to 50.

14

Checksum for bytes 12,
13
big-endian, int16

1

Gain Factor
Gain factor to amplify or to attenuate the NOx index output.
Allowed values are in range 1..1000. The default value is 230.

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Checksum for bytes 15,
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6.1.10 Read/ Write RH/T Acceleration Mode (0x60F7)
By default, the RH/T acceleration algorithm is optimized for a sensor which is positioned in free air. If the sensor is
integrated into another device, the ambient RH/T output values might not be optimal due to different thermal behavior.
This parameter can be used to adapt the RH/T acceleration behavior for the actual use-case, leading in an
improvement of the ambient RH/T output accuracy. There is a limited set of different modes available, each identiﬁedby a number:• 0: Low Acceleration• 1: High Acceleration• 2: Medium Acceleration
Medium and high accelerations are particularly indicated for air quality monitors which are subjected to large
temperature changes. Low acceleration is advised for stationary devices not subject to large variations in temperature.
This parameter can be changed in any state of the device, but it is applied only the next time starting a measurement,i.e., when sending a "Start Measurement" command. So, the parameter needs to be set before a new measurement isstarted.
Read/Write Data and Parameters:

Byte #
0..1
2

Datatype
big-endian, uint16

Scale factor
1

Description
RH/T acceleration mode.

Checksum for bytes 0, 1

6.1.11 Read/ Write VOC Algorithm State (0x6181)
Allows to backup and restore the VOC algorithm state to resume operation after a short interruption, skipping initial
learning phase. By default, the VOC algorithm resets its state to initial values each time a measurement is started,even if the measurement was stopped only for a short time. So, the VOC index output value needs a long time until it isstable again. This can be avoided by restoring the previously memorized algorithm state before starting the measure
mode.
Read/Write Data and Parameters:

Byte #
0..1
2

Datatype
Bytearray8

Scale factor
1

Description
VOC algorithm state.

Checksum for bytes 0, 1

…
9..10

Bytearray811

Checksum for bytes 9, 101

6.1.12 Start Fan Cleaning (0x5607)
Starts the fan-cleaning manually. This command can only be executed in Measurement-Mode. For more details, notethe explanations given in 5.2 Fan Auto Cleaning.
6.1.13 Read/Write Auto Cleaning Interval (0x8004)
Reads/Writes the interval [s] of the periodic fan-cleaning. For more details, note the explanations given in 5.2 Fan Auto
Cleaning. Please note that since this configuration is volatile, it will be reverted to the default value after a device reset.

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Read/Write Data and Parameters:

Byte #
0, 1
2
3, 4
5

Description
Most Significant Byte
Checksum for bytes 0, 1
Least Significant Byte
Checksum for bytes 3, 4

big-endian, unsigned 32-bit integer value:
Auto Cleaning Interval [s]6.1.14 Read Product Name (0xD014)
This command returns the product name SEN5x (SEN50, SEN54 or SEN55). It is defined as a string value with amaximum length of 32 ASCII characters (including terminating null-character).
Read/Write Data:

Byte #
0
1
2
…
45
46
47

Description
ASCII Character 0
ASCII Character 1
Checksum for bytes 0, 1…
ASCII Character 30
ASCII Character 31
Checksum for bytes 45, 46

6.1.15 Read Serial Number (0xD033)
This command returns the requested serial number. It is defined as a string value with a maximum length of 32 ASCII
characters (including terminating null-character).
Read/Write Data:

Byte #
0
1
2
…
45
46
47

Description
ASCII Character 0
ASCII Character 1
Checksum for bytes 0, 1…
ASCII Character 30
ASCII Character 31
Checksum for bytes 45, 46

6.1.16 Read Firmware Version (0xD100)
Get firmware version.
Read/Write Data:

Byte #
0
1

Description
Firmware version
Reserved

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2

Checksum for bytes 0, 1

6.1.17 Read Device Status (0xD206)
Use this command to read the Device Status Register. For more details, note the explanations given in section 5.4
Device Status Register.
Read/Write Data:

Byte #
0, 1
2
3, 4
5

Description
Most Significant Byte
Checksum for bytes 0, 1
Least Significant Byte
Checksum for bytes 3, 4

big-endian, unsigned 32-bit integer value:
Device Status Register

6.1.18 Clear Device Status (0xD210)
Clears all flags in device status register.
6.1.19 Device Reset (0xD304)
Device software reset command. After calling this command, the module is in the same state as after a power reset.

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7 Technical Drawings
7.1 Product outline drawings

Figure 7: Package outline dimensions (given in mm) of the SEN5x.

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7.2 Product LabelThe SEN5x contains a label (size: 18 x 12 mm) which is attached to one side of the sensor and contains the following
information:
Label Design

Label Content
SEN5x
SDN-T
xxxxxxxxxxxxxxxx / S

Description
Product nameSensirion internal marking
16-digit decimal serial number

Table 13 Label information.

label
position

Figure 8: Indication of label position on SEN5x.

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8 Revision History
Date
January 2022
March 2022

VersionPage(s)Changes

1
2

4
9-10

Initial version
Updated table
Added Recommended and Absolute Maximum/Minimum Operating andStorage Conditions for SEN55 and SEN50
Updated flowchart and description of operating modes
Updated names for the RH/T Acceleration Mode parameters

14
23

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9 Important Notices
Warning, Personal Injury
Do not use this product as safety or emergency stop devices or in any other application where failure of the
product could result in personal injury. Do not use this product for applications other than its intended andauthorized use. Before installing, handling, using or servicing this product, please consult the data sheet andapplication notes. Failure to comply with these instructions could result in death or serious injury.
If the Buyer shall purchase or use SENSIRION products for any unintended or unauthorized application, Buyer shalldefend, indemnify and hold harmless SENSIRION and its officers, employees, subsidiaries, affiliates and distributors
against all claims, costs, damages and expenses, and reasonable attorney fees arising out of, directly or indirectly, any
claim of personal injury or death associated with such unintended or unauthorized use, even if SENSIRION shall beallegedly negligent with respect to the design or the manufacture of the product.
ESD Precautions
The inherent design of this component causes it to be sensitive to electrostatic discharge (ESD). To prevent ESDinduced damage and/or degradation, take customary and statutory ESD precautions when handling this product.
See application note “ESD, Latchup and EMC” for more information.
Warranty
SENSIRION warrants solely to the original purchaser of this product for a period of 12 months (one year) from the dateof delivery that this product shall be of the quality, material and workmanship defined in SENSIRION’s publishedspecifications of the product. Within such period, if proven to be defective, SENSIRION shall repair and/or replace thisproduct, in SENSIRION’s discretion, free of charge to the Buyer, provided that: notice in writing describing the defects shall be given to SENSIRION within fourteen (14) days after theirappearance;
 such defects shall be found, to SENSIRION’s reasonable satisfaction, to have arisen from SENSIRION’s faulty
design, material, or workmanship;
 the defective product shall be returned to SENSIRION’s factory at the Buyer’s expense; and the warranty period for any repaired or replaced product shall be limited to the unexpired portion of the original
period.
This warranty does not apply to any equipment which has not been installed and used within the specifications
recommended by SENSIRION for the intended and proper use of the equipment. EXCEPT FOR THE WARRANTIESEXPRESSLY SET FORTH HEREIN, SENSIRION MAKES NO WARRANTIES, EITHER EXPRESS OR IMPLIED,WITH RESPECT TO THE PRODUCT. ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION,WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE EXPRESSLYEXCLUDED AND DECLINED.
SENSIRION is only liable for defects of this product arising under the conditions of operation provided for in the data
sheet and proper use of the goods. SENSIRION explicitly disclaims all warranties, express or implied, for any period
during which the goods are operated or stored not in accordance with the technical specifications.
SENSIRION does not assume any liability arising out of any application or use of any product or circuit and specificallydisclaims any and all liability, including without limitation consequential or incidental damages. All operating
parameters, including without limitation recommended parameters, must be validated for each customer’s applications
by customer’s technical experts. Recommended parameters can and do vary in different applications.
SENSIRION reserves the right, without further notice, (i) to change the product specifications and/or the information inthis document and (ii) to improve reliability, functions and design of this product.
Copyright © 2021, by SENSIRION. CMOSens® is a trademark of Sensirion. All rights reserved

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Headquarters and Subsidiaries
Sensirion AG
Laubisruetistr. 50
CH-8712 Staefa ZH
Switzerland

Sensirion Inc., USA
phone: +1 312 690 5858
info-us@sensirion.com
www.sensirion.com

Sensirion Korea Co. Ltd.
phone: +82 31 337 7700~3
info-kr@sensirion.com
www.sensirion.com/kr

phone: +41 44 306 40 00
fax:+41 44 306 40 30
info@sensirion.com
www.sensirion.com

Sensirion Japan Co. Ltd.
phone: +81 3 3444 4940
info-jp@sensirion.com
www.sensirion.com/jp

Sensirion China Co. Ltd.
phone: +86 755 8252 1501
info-cn@sensirion.com
www.sensirion.com/cn

Sensirion Taiwan Co. Ltd
phone: +886 3 5506701
info@sensirion.com
www.sensirion.com

To find your local representative, please visit www.sensirion.com/distributors

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