www.sensirion.com Version 1.3 – January 2013 1/9
SFM4100 Series
Low-cost Digital Mass Flow Meter for Gases
Accuracy 3% m.v.
Digital output (I2C)
Multigas option available
Calibrated and temperature compensated
Excellent long-term stability
Downmount or legris carstick fittings
Product Summary
The SFM4100 gas flow meter series is designed as a
versatile OEM gas flow meter for demanding volume
applications.
The SFM4100 is designed to measure Air and non-
aggressive gases with excellent accuracy over a large
dynamic range. Mass flows ranges up to 20 slm are
available. The SFM4100 series operates with supply
voltage 5-9 VDC and through its digital I2C interface it can
be easily embedded into a microprocessor environment.
The sturdy design of the SFM4100 sensor allows for
operation pressures up to 10 barg. The flow signal is
internally lineralized and temperature compensated.
The outstanding performance of these sensors is based
on Sensirion’s patented CMOSens® sensor technology,
which combines the sensor element, signal processing
and digital calibration on a single microchip. The mass
flow is measured by a thermal method on the MEMS
sensor element. Compared to other thermal mass flow
sensors (MEMS, hotwire or capillary type) the SFM4100
features an extended dynamic range, higher long-term
stability, and improved repeatability.
The well-proven CMOS technology is perfectly suited for
high-quality mass production and is the ideal choice for
demanding and cost-sensitive OEM applications.
Applications
Medical (e.g. respiratory care, anesthesia)
Analytical Instruments
Leak testing
Process automation
Connection diagram
Sensor chip
The SFM4100 series features a fourth-generation silicon
sensor chip called SF04. In addition to a thermal mass
flow sensor element, the chip contains an amplifier, A/D
converter, EEPROM memory, digital signal processing
circuitry, and interface. The highly sensitive chip is
particularly sensitive at lowest flows, giving the SFM4100
sensor its large dynamic range.
SFM4100 OEM options
A variety of custom options such as other analog output,
different gases, flow ranges, multigas calibration can be
implemented for high-volume OEM applications
(>1000pc/y). Ask us for more information.
C
(master)
VDD=3.5-9V
VLS=2.9-5.5V
VDD
GND
SDA
SCK
SFM4100 series with bidirectional digital communication
(I2C bus)
www.sensirion.com Version 1.3 – January 2013 2/9
1. Sensor Performance
1.1 Physical specifications
Parameter 1
SFM4100
Measurement range
0-20 slm2
Calibration available
Air, N2, O2, N2O, Ar or CO2
Resolution
12 bits preset
(for 9–16 bits see documentation)
Zero point accuracy3,4
0.03 slm
Accuracy3,4
0.15% of full scale or 3% of reading,
whichever is bigger
Span repeatability
0.25% of reading or 5 sccm whichever
is bigger
Offset shift due to
temperature variation
2 sccm / °C
Span shift due to
temperature variation
< 0.1% of reading per °C
Offset stability
< 0.01 slm/year
Pressure drop at full
flow
<25mbar
Response time
4.6 ms @ 12-bit resolution
(See documentation for response times with
other resolutions, e.g. 1.3 ms with 10 bits)
Warm-up time for first
reliable measurement
Max. 500ms
in general 50 ms
1 Unless otherwise noted, all sensor specifications are at 23°C and
absolute pressure = 4,8 bar.
2 Reference conditions for standard liters per minute slm: 20°C,
1013mbar; sccm denotes standard cubic centimeters per minute
3 includes repeatability and hysteresis.
4 The zero-point accuracy and span accuracy are independent
uncertainties and add according to the principles of error propagation.
1.2 Ambient conditions
Parameter
SFM4100 Series
Media compatibility5
Noncorrosive gases and gas
mixtures
Limited media compatibility
corrosive Gases6
Calibrated temperature range5
0 °C to +50 °C
Operating temperature
-20 °C to +80 °C
Storage temperature5
-40 °C to +80 °C
Operating Pressure Range
0-6 bar gauge
Position sensitivity
Use flow horizontally, electronic
connector up
5 Contact Sensirion for information about other gases, wider calibrated
temperature ranges and higher storage temperatures.
6 For a limited time period, depending on chemical. Not recommended.
1.3 Materials
Parameter
SFM4100 Series
Wetted materials
Si, Si3N4, SiOx, Gold, Viton®, Epoxy, PA-
12, Stainless Steel, Nickel Plated Brass,
Nylon, Nitrile, coated Aluminium,
Oxygenoex
RoHS
fully RoHS compliant
2. Electrical Specifications
2.1 Power supply
The SFM4100 series sensors require a supply voltage
(VDD) between 3.5V and 9 V. For the power supply of the
level shifter (VLS) a voltage between 2.9V and 5.5V is
required. Please be aware that the VLS must be the same
as the voltage of SCK.
2.2 Electrical characteristics
Parameter
SFM4100
Supply voltage
3.5 – 9.0 VDD
Level Shifter Supply7
2.9 -5.5 VLS
Current drain
< 12.5 mA typical in operation
Interface
Digital 2-wire interface (I2C)
Bus clock frequency
SCL: 100 kHz typical
Default I2C address
per gas type
Air: 1 (0000001)
O2: 2 (0000010)
CO2: 3 (0000011)
N2O: 4 (0000100)
Ar: 5 (0000101)
Flow output signal
Flow in sccm = value received 1
Flow in slm = value received / 1000
7 Same voltage as the communication level of the P is required.
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3. Interface Specifications
The serial interface of the SFM4100 series is optimized in
terms of sensor readout and power consumption. It is
compatible with I2C interfaces. For detailed specifications
of the I2C protocol, see The I2C Bus Specification,
Version 2.1, January 2000 (source: NXP).
(www.nxp.com/products/interface_control/i2c)
3.1 Interface connection – external
components
Bi-directional bus lines are implemented by the devices
(master and slave) using open-drain output stages and a
pull-up resistor connected to the positive supply voltage.
The recommended pull-up resistor value depends on the
system setup (capacitance of the circuit or cable and bus
clock frequency). In most cases, 10 kΩ is a reasonable
choice.
The capacitive loads on SDA and SCL line have to be the
same. It is important to avoid asymmetric capacitive loads.
I2C Transmission Start Condition
SDA
SCL
VDD
master slave (SDP600)
Rp Rp
Both bus lines, SDA and SCL, are bi-directional and therefore
require an external pull-up resistor.
3.2 I2C Address
The I2C address consists of a 7-digit binary value. By
default, the I2C address of the SFM4100 is gas specific
(see chapter 2.2). The address is always followed by a
write bit (0) or read bit (1).
3.3 Transfer sequences
Transmission START Condition (S): The START condi-
tion is a unique situation on the bus created by the master,
indicating to the slaves the beginning of a transmission
sequence (the bus is considered busy after a START).
I2C Transmission Start Condition
S
START condition
SDA
SCL
A HIGH to LOW transition on the SDA line while SCL is HIGH
Transmission STOP Condition (P): The STOP condition
is a unique situation on the bus created by the master,
indicating to the slaves the end of a transmission
sequence (the bus is considered free after a STOP).
I2C Transmission Stop Condition
P
STOP condition
SDA
SCL
A LOW to HIGH transition on the SDA line while SCL is HIGH.
Acknowledge (ACK) / Not Acknowledge (NACK): Each
byte (8 bits) transmitted over the I2C bus is followed by an
acknowledge condition from the receiver. This means that
after the master pulls SCL low to complete the
transmission of the 8th bit, SDA will be pulled low by the
receiver during the 9th bit time. If after transmission of the
8th bit the receiver does not pull the SDA line low, this is
considered to be a NACK condition.
If an ACK is missing during a slave to master transmission,
the slave aborts the transmission and goes into idle mode.
I2C Acknowledge / Not Acknowledge
ACK
SCL R/_W D7 D0 ACK
SDA
not acknowledge
acknowledge
Each byte is followed by an acknowledge or a not
acknowledge, generated by the receiver
Handshake procedure (Hold Master): In a master-slave
system, the master dictates when the slaves will receive or
transmit data. However, in some situations a slave device
may need time to store received data or prepare data to
be transmitted. Therefore, a handshake procedure is
required to allow the slave to indicate termination of
internal processing.
I2C Hold Master
ACK
SCL R/_W D7 D0 ACK
SDA
Hold master:
SCK line pulled LOW data ready: SCK line released
After the SCL pulse for the acknowledge signal, the SFM4100
series sensor (slave) can pull down the SCL line to force the
master into a wait state. By releasing the SCL line, the sensor
indicates that its internal processing is completed and
transmission can resume. (The bold lines indicate that the
sensor controls the SDA/SCL lines.)
SFM4100
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3.4 Data transfer format
Data is transferred in byte packets in the I2C protocol,
which means in 8-bit frames. Each byte is followed by an
acknowledge bit. Data is transferred with the most
significant bit (MSB) first.
A data transfer sequence is initiated by the master
generating the Start condition (S) and sending a header
byte. The I2C header consists of the 7-bit I2C device
address and the data direction bit (R/_W).
The value of the R/_W bit in the header determines the
data direction for the rest of the data transfer sequence. If
R/_W = 0 (WRITE) the direction remains master-to-slave,
while if R/_W = 1 (READ) the direction changes to slave-
to-master after the header byte.
4. Command Set and Data Transfer
Sequences
A command is represented by an 8-bit command code.
The data direction may not change after the command
byte, since the R/_W bit of the preceding I2C header has
already determined the direction to be master-to-slave. In
order to execute commands in Read mode using I2C, the
following principle is used. On successful (acknowledged)
receipt of a command byte, the sensor stores the
command nibble internally. The Read mode of this
command is then invoked by initiating an I2C data transfer
sequence with R/_W = 1.
If a correctly addressed sensor recognizes a valid
command and access to this command is granted, it
responds by pulling down the SDA line during the
subsequent SCL pulse for the acknowledge signal (ACK).
Otherwise it leaves the SDA line unasserted (NACK).
The two most important commands are described in this
data sheet, and the data transfer sequences are specified.
Contact Sensirion for advanced sensor options.
4.1 Measurement triggering
Each individual measurement is triggered by a separate
read operation.
Note that two transfer sequences are needed to perform a
measurement. First write command byte hF1 (trigger
measurement) to the sensor, and then execute a read
operation to trigger the measurement and retrieve the flow
or differential pressure information.
On receipt of a header with R/_W=1, the sensor generates
the Hold Master condition on the bus until the first
measurement is completed (see Section 3.3 for timing).
After the Hold Master condition is released, the master
can read the result as two consecutive bytes. A CRC byte
follows if the master continues clocking the SCL line after
the second result byte. The sensor checks whether the
master sends an acknowledge after each byte and aborts
the transmission if it does not.
I2C Measurement
8-bit command code: hF1
Command: Trigger flow measurement
1312 18 19 2221 27
MSByte MeasData LSByte MeasData
11 14 15 16 17 20 23 24 25 26
ACK
ACK
28 3130 36
Check Byte
29 32 33 34 35
1 2 3 4 5 6 7 8
ACK
9 18
S
I2CAdr
ACK
S
ACK
W
123456789
10
Hold Master
P
ACK
10 11 12 13 14 15 16 17
11110001
Command
1 0 0 0 0 0 0
R
1000000
I2CAdr
0 1
Hatched areas indicate that the sensor controls the SDA line.
4.2 Soft reset
This forces a sensor reset without switching the power off
and on again. On receipt of this command, the sensor
reinitializes the control/status register contents from the
EEPROM and starts operating according to these settings.
I2C Soft Reset
8-bit command code: hFE
Command: Soft reset
1 2 3 4 5 6 7 8
S
9
ACK
ACK
18
system reboot
10 11 12 13 14 15 16 17
I2CAdr W
1 0 0 0 0 0 0 1 1 1 1
Command
11100
4.3 CRC-8 Redundant Data Transmission
Cyclic redundancy checking (CRC) is a popular technique
used for error detection in data transmission. The
transmitter appends an n-bit checksum to the actual data
sequence. The checksum holds redundant information
about the data sequence and allows the receiver to detect
transmission errors. The computed checksum can be
regarded as the remainder of a polynomial division, where
the dividend is the binary polynomial defined by the data
sequence and the divisor is a “generator polynomial”.
The SF04 sensor implements the CRC-8 standard based
on the generator polynomial
x8 + x5 + x4 +1.
Note that CRC protection is only used for date transmitted
from the slave to the master.
For details regarding cyclic redundancy checking, please
refer to the relevant literature.
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5. Conversion to Physical Values
5.1 Signal scaling and physical unit
The calibrated signal read from the sensor is a signed
INTEGER number (two's complement number). The
INTEGER value can be converted to the physical value by
dividing it by the scale factor (mass flow = sensor output
scale factor). The scale factor is specified in Section 2.2.
5.2 Temperature compensation
The SFM4100 sensor series features digital temperature
compensation. The temperature is measured on the
CMOSens® chip by an on-chip temperature sensor. This
data is fed to a compensation circuit that is also integrated
on the CMOSens® sensor chip. No external temperature
compensation is necessary.
6. OEM Options
A variety of custom options can potentially be
implemented for high-volume OEM applications. None of
these options is available with the standard sensors.
Contact Sensirion for more information.
6.1 Switch function
A switch version with a programmable trigger level and
programmable hysteresis can be realized.
6.2 Temperature measurement
The sensor temperature can be read out via the digital
interface.
6.3 Minimized power consumption
For low-power applications, the current consumption can
be reduced to approximately 3.5mA.
6.4 Broken sensor element detection
Breakage of the sensor element can be detected by a
sensor chip self-test.
6.5 Plausibility checks
An OEM version of the sensor can be configured to provide
certain plausibility checks triggered by a microprocessor. This
can be used to create a combined sensor/microprocessor
system that can be certified as fail-safe.
6.6 Multigas / Multirange Option
The Sensor can be calibrated for the use with multiple
Gases and/or for multiple flow ranges.
6.7 Gas Mixture Detection
In combination with a external microprocessor the Sensor
can be used to also asses the concentration of many two
gas mixtures. This feature can be made available for high
volume applications. Please contact Sensirion for details.
6.8 Customer-specific interface
For analog voltage output, please contact Sensirion.
www.sensirion.com Version 1.3 – January 2013 6/9
7. Mechanical Specifications
7.1 Mechanical concept
The SFM4100 Series is designed for both through-hole
technology hand-soldered to a PCB or downmount
configuration for mounting on the manifold.
For mounting on a basis plate 4 screw holes (Ø=3.42mm)
are available (see Figure 1: position 0/0).
The flow connection is realized with Legris carstick 6mm
quick connectors, and thus standard-size plastic tubes
(OD 6 mm) are best used.
7.2 Mechanical characteristics
Parameter
Flow connector
Legris Carstick 6mm / Downmount
Electrical connector
E-Tec: SL2-008-SH108/01-55B or
Samtec: HTSW-104-07-6.D
Allowable
overpressure
10 bar
Rated burst pressure
> 20 bar
Weight
< 60 g
7.3 SFM4100 – Physical Dimensions
Figure 1: Straight-through flow channel geometry (all
dimensions are in mm)
Figure 2: Downmount version with 90° angle (all dimensions are
in mm)
7.4 Pin Layout
Figure 3: Pin Layout SFM4100
Gas Flow
Pin 1
www.sensirion.com Version 1.3 – January 2013 7/9
7.5 Pin assignments
.
Figure 4: Digital output pin assignments (top view)
7.6 Electrical Connection
The SFM4100 Sensor has a 8 pin 2.54 mm pitch electrical
connector (E-Tec: SL2-008-SH108/01-55B).
The following connectors can be used as corresponding
sockets :
for direct PCB mounting of the SFM4100
Through Hole: Digikey: S7107-ND
SMD: Digikey: S5713-ND
with ribbon cable connector
Digikey: 609-3568-ND
Mouser: 649-71600-008LF
corresponding ribbon cable
Mouser: 517-3365/08-300SF
Farnell: 9187111
The cable length from the sensor to the microprocessor is
recommended to be below 30 cm. In case longer cable
length is required, please contact Sensirion.
7.7 Sensor handling
The sensors of the SFM4100 series are designed to be
robust and vibration resistant. Nevertheless, the accuracy
of the high-precision SFM4100 series can be degraded by
rough handling. Sensirion does not guarantee proper
operation in case of improper handling. Note: avoid
applying any mechanical stress to the solder joints of the
sensor during or as a result of PCB assembly.
The sensor ships in an antistatic package to prevent
electrostatic discharge (ESD), which can damage the part.
To avoid such damage, ground yourself using a grounding
strap or by touching a grounded object. Furthermore store
the parts in the antistatic package when not in use.
7.8 Packaging, Labeling
Housing: The sensor housing consists of Grillamid (PA12).
The device is fully RoHS compliant – it is free of Pb, Cd,
Hg, Cr(6+), PBB and PBDE.
Each sensor is labelled on the front side:
Traceability Information: SFM4xxx are shipped in trays
of 10pcs with 4 trays per box. The tray dimension is
355mm x 255mm x 21.5mm. Each Sensor is traceable
through its unique serial number.
Sensor type
Sensirion item # (plain
& barcode)
Ser. # (plain &
barcode)
Calib. Gas / max flow /
fitting
Reference conditions
Figure 5: Label sticking on each sensor
8. Ordering Information
Use the part names and item numbers shown in the
following table when ordering SFM4100 series mass flow
sensors. For the latest product information and local
distributors, visit www.sensirion.com.
Part name
Gas
Calibrated
range
Item number
Legris
Downmount
SFM4100
Air; N2
0-20 slm
1-100688-02
1-100890-02
SFM4100
O2
0-20 slm
1-100686-02
1-100888-02
SFM4100
CO2
0-20 slm
1-100687-02
1-100889-02
SFM4100
N2O
0-20 slm
1-100684-02
1-100886-02
SFM4100
Ar
0-20 slm
1-100685-02
1-100887-02
SFM7xxx
OEM
OEM
tbd
Packaging units: 10 items/tray and 40 items/box.
MOQ: 1 box = 40 Sensors of the same type.
Pin Number
Definition
Pin 1
Sensor Supply voltage
VDD: 3.5-9 V
Pin 2
Not connected
Pin 3
Level shifter supply voltage
VLS: 2.9-5.5 V
Pin 4
GND
Pin 5
Bus Clock Line
SCL: 10-120 kHz
Pin 6
GND
Pin 7
Data Line / SCK
Pin 8
GND
SFM4100-Air www. sensirion.com
1-100XXX-02 Made in Switzerland
╽║║║║▎▏╽║║▕║║▍▎▏╽║║╿▎▏
Air
09320023 20slm
╽║║║║▎▏╽║║▕║║▍▎▏╽║║╿▎▏
fitting
20°C, 1013 mbar
VDD
VLS
SCK
www.sensirion.com Version 1.3 – January 2013 8/9
9. Safety Precautions
Do not use this product as safety or emergency stop device
or in any other application where failure of the product could
result in personal injury. Failure to comply with these
instructions could result in death or serious injury.
10. Revision history
Date
Version
Changes
September 2009
V1.0
Initial release
June 2010
V1.1
Correction of I2C address
September 2010
V1.2
Several corrections
January 2013
V1.3
Item number update, manifold version
added, improved accuracy, other
corrections
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 (including death). Do not use this product for
applications other than its intended and authorized use. Before
installing, handling, using or servicing this product, please
consult the datasheet and application 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 shall defend, 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 be
allegedly 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 ESD-induced damage and/or
degradation, take customary and statutory ESD precautions when
handling this product.
Warranty
SENSIRION warrants solely to the original purchaser of this product for
a period of 12 months (one year) from the date of delivery that this
product shall be of the quality, material and workmanship defined in
SENSIRION’s published specifications of the product. Within such
period, if proven to be defective, SENSIRION shall repair and/or
replace this product, 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 their appearance;
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 WARRANTIES EXPRESSLY 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 EXPRESSLY EXCLUDED AND DECLINED.
SENSIRION is only liable for defects of this product arising under the
conditions of operation provided for in the datasheet 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 specifically disclaims 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 in this document and (ii) to
improve reliability, functions and design of this product.
Copyright© 2001-2009, SENSIRION.
CMOSens® is a trademark of Sensirion
All rights reserved
RoHS and WEEE Statement
The SFM4100 Series complies with requirements of the following
directives:
EU Directive 2002/96/EC on waste electrical and electronic
equipment (WEEE), OJ13.02.2003; esp. its Article 6 (1) with
Annex II.
EU Directive 2002/95/EC on the restriction of the use of certain
hazardous substances in electricaland electronic equipment
(RoHS), OJ 13.02.2003; esp. its Article 4.
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Headquarter and Sales Offices
Headquarter
SENSIRION AG Phone: +41 44 306 40 00
Laubisruetistr. 50 Fax: +41 44 306 40 30
CH-8712 Staefa ZH info@sensirion.com
Switzerland http://www.sensirion.com/
Sales Office USA:
SENSIRION Inc. Phone: +1 805 409 4900
2801 Townsgate Rd., Suite 204 Fax: +1 805 435 0467
Westlake Village, CA 91361 michael.karst@sensirion.com
USA http://www.sensirion.com/
Sales Office Japan:
SENSIRION JAPAN Co. Ltd. Phone: +81 3 3444 4940
Postal Code: 108-0074 Fax: +81 3 3444 4939
Shinagawa Station Bldg. 7F, info@sensirion.co.jp
4-23-5, Takanawa, Minato-ku http://www.sensirion.co.jp
Tokyo, Japan
Sales Office Korea:
SENSIRION KOREA Co. Ltd. Phone: +82 31 440 9925~27
#1414, Anyang Construction Tower B/D, Fax: +82 31 440 9927
1112-1, Bisan-dong, Anyang-city info@sensirion.co.kr
Gyeonggi-Province http://www.sensirion.co.kr
South Korea
Sales Office China:
Sensirion China Co. Ltd. phone: +86 755 8252 1501
Room 2411, Main Tower fax: +86 755 8252 1580
Jin Zhong Huan Business Building, info@sensirion.com.cn
Futian District, Shenzhen, www.sensirion.com.cn
Postal Code 518048
PR China
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