SFM4100-AIR-N2 DOWNMOUNT - SENSIRION

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.

www.sensirion.com Version 1.3 – January 2013 3/9

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

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

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

www.sensirion.com Version 1.3 – January 2013 4/9

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

28 3130 36

Check Byte

29 32 33 34 35

1 2 3 4 5 6 7 8

ACK

9 18

I2CAdr

ACK

123456789

Hold Master

ACK

10 11 12 13 14 15 16 17

11110001

Command

1 0 0 0 0 0 0

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

ACK

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.

www.sensirion.com Version 1.3 – January 2013 5/9

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

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

0-20 slm

1-100685-02

1-100887-02

SFM7xxx

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.

CMOSens® is a trademark of Sensirion

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.

www.sensirion.com Version 1.3 – January 2013 9/9

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