1-100011_技术文档

ASF1400

Bidirectional Mass Flow Meter

_ Unique dynamic range:

0.01 sccm – 400 sccm

_ Outstanding resolution and accuracy

_ Ultra fast response time

_ Hysteresis & offset free

_ Calibrated & temperature compensated

_ RS-232 and SPI digital interface

Preliminary Information as of November 2001

ASF1400 Product Summary

The ASF1400 Mass Flow Meter enables extremely

accurate bidirectional measurement of gas flow over four

orders of magnitude. Its leading performance is based

on SENSIRION’s unsurpassed CMOSens™ sensor

technology. With CMOSens™, the on-chip sensor

element forms an integrated whole with the amplification

and A/D converter circuit. This results in superior

resolution, fast response time and large dynamic range

at lowest power consumption.

Mounted in rugged, chemically inert PBT housing the

ASF1400 is suitable for a wide range of applications.

Such include mass flow metering for process control,

medical applications, heating ventilation and air

conditioning (HVAC) solutions, as well as gas flow

metrology.

The sensor housing provides two inlets for measuring

the gas flow and withstands overpressures of 2 bar (29

psi).

All measurement data is fully calibrated and temperature

compensated by means of an internal microcontroller.

The ASF1400 requires a supply voltage of 7…18Vdc

and provides an RS-232 and SPI compliant electrical

interface.

ASF1400 MASS FLOW METER

GND

VDD

Power

VOLTAGE

MASS FLOW

Supply

REGULATOR

/CS

CMOSens™ SENSOR CHIP

MICRO

SPI

MOSI

MISO

SCK

CONTROLLER

Interface

RS232 LINE

DRIVER/

RxD

TxD

RS232

Interface

RECEIVER

EEPROM

MASS FLOW

Figure 1: Block Diagram ASF1400 Mass Flow Sensor with CMOSens™ technology.

www.sensirion.com

Sensirion AG, Eggbuhlstr. 14, 8052 Zurich, Switzerland, Phone: +41 1 306 40 00, Fax: +41 1 306 40 30

ASF1400 Bidirectional Mass Flow Meter

Introductory Description

The heart of the ASF1400 mass flow meter is

powered by Sensirion’s unsurpassed CMOSens

sensor technology. The ASF1400 mass flow meter

therefore provides unbeatable performance at very

attractive system cost. The lowest detectable gas flow

rate is 0.003 sccm, which means a minimum volume

In general, all gas types can be measured using the

ASF1400 product. However, the standard calibration

gas is nitrogen. Please contact SENSIRION, if you

would like to use the sensor for applications with other

gases.

To get you started quickly, an evaluation package

including ASF1400 devices, software, cables, rubber

hose and bypass is available from Sensirion AG.

3

of 3 mm gas per minute can be measured. Covering

at the same time a flow range of more than 4 orders

of magnitude, the ASF1400 sets a new standard

wherever mass flow has to be measured or

controlled.

CMOSens sensor technology

CMOSens is the base technology for all Sensirion

multi sensor modules and sensor systems. The

unification of semiconductor chip and sensor

technology serves as a platform for highly integrated

system solutions with excellent sensor precision and

reliability. With CMOSens, the on-chip sensor

element forms an integrated whole with a high-end

amplification and A/D converter circuit. Due to the

compact single-chip design, CMOSens based

sensors are very resistant to electromagnetic

disturbances (EMC), another important technical

advantage of this state of the art sensor technology.

As a result, CMOSens based multi sensor modules

offer excellent sensor precision, fast response time

and a very large dynamic measurement range. In

addition, the digital intelligence of the CMOSens

sensor technology enables digital interfaces that

permit an easy link with the system of the customer, a

real advantage and benefit that results in ready-to-use

problem solutions (“Mount&Sense”).

The ASF1400 device measures true mass flow

independent of the ambient temperature and pressure

changes. You simply connect the gas to be measured

to the ASF1400 device to get an instantaneous gas

flow rate at a sampling rate of up to 7Hz (please

contact us for sampling rates of up to 200Hz).

A flow range between ±400 sccm can directly be

mea-sured by connecting the ASF1400. To increase

the range, a bypass can be used in conjunction with

the ASF1400 device (see Section 1.4 of this data

sheet).

In addition to mass flow, the ASF1400 device

provides information about the temperature on the

CMOSens sensor element. Both mass flow and

temperature data are accessed through an RS-232 or

SPI interface. The RS-232 interface allows you to

directly connect the ASF1400 device to a PC or PDA

using standard terminal software. The serial

peripheral interface (SPI) also enables the ASF1400

to be used in smaller systems. If a special interface

such as 4-20 mA current output or other is required

contact Sensirion for a customer specific solution.

www.sensirion.com

November 2001 Preliminary Information

2/11

ASF1400 Bidirectional Mass Flow Meter

1 Mass Flow Sensor Performance

Table 1: Overview of ASF1400 Gas Sensor Performance

Maximu

m

Parameter

Condition

Minimum

Typical

Units

Flow Sensor

(1)

direct measurement

using proposed bypass tube

customized bypass tube

400 sccm flow

-400

-100

unlimited

400

100

unlimited

sccm

(2)

(3)

Dynamic Range

Resolution

liter/min

0.09

0.01

sccm

< 10 sccm flow

Lowest

(4)

< 10 sccm flow

0.015

0.003

sccm

Detectable Flow

Pressure Drop

(5)

400 sccm, p_abs.= 1 bar

120

Pa

(6)

0.0025 % FS

Repeatability

0.025 % m.v.

(7)

0…5 % of full scale

0.05 % FS

Accuracy

23 C

23°C

(7)

5…100 % of full scale

1 % m.v.

Offset

< 0.005

< 0.02

2

% FS

bar

Overpressure

(8)

Resistance

Response Time

depends on resolution setting

(see Section 3, Table 2)

142

0

1280

70

ms

°C

(9)

Operating

Temperature

Ambient

Zero

< 0.005

< 0.08

% FS / °C

% measured value /

°C

Temperature

Coefficient

Span

Position

p_abs=1 bar, small nitrogen flow

±0.008

% FS

Sensitivity

Temperature

Sensor

(10)

Measures temperature inside the sensor, but not of the surrounding air

Dynamic Range

0

70

°C

Resolution

Accuracy

0.1

2

3

Notes:

All data for 23°C unless otherwise noted.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

3

1 sccm = 1 cm /min at 0°C and 1013mbar pressure (1sccm = 0.001 norm liter)

using bypass tube included in Sensirion’s mass flow meter evaluation kit EK-F1

1 liter/min = 1000 sccm

0.015 sccm is standard ASF1400, 0.003 sccm is available on request.

1 bar = 100 000 Pa = 0.9869 atm = 401.9 inch H₂O = 14.5 psi

Error = % of full scale (FS) or % of measured value, whichever is bigger.

Better calibration available on request. Allow the Sensor to warm up for best results.

Higher overpressure resistance can be realised in OEM-solutions.

For faster response times please check out the ASF1430 high speed mass flow meter data sheet

The sensor warms up by about 7°C (depending on supply voltage and ventilation).

www.sensirion.com

November 2001 Preliminary Information

3/11

ASF1400 Bidirectional Mass Flow Meter

1.1 Gas Flow Characteristics

Figure 2 shows the applied gas flow vs. the digital

output of the ASF1400.

1.3 Gas Flow and Pressure Difference

The ASF1400 is calibrated for mass flow

measurements. However, there is a well defined

relation between mass flow and pressure drop. This

relation is shown in Figure 4. On request the

ASF1400 can also be calibrated for the pressure drop

at its output (for more details refer to the

documentation of the Sensirion Differential Pressure

Sensor ASP1400).

500

250

0

-250

-500

150

100

50

-500

-250

0

250

500

Mass Flow [sccm]

Figure 2: ASF1400 transfer characteristics.

1.2 Sensor Principle and Gas Types

0

-50

-100

-150

The ASF1400 device detects mass gas flow by

measuring heat transfer. A heating resistor on a

thermally insulated membrane is kept above ambient

temperature. In the presence of gas flow, the

temperature distribution up- and downstream is

disturbed. This asymmetry is then measured. Due to

the minimal thermal mass of the membrane,

symmetrical arrangement, and accurate temperature

measurement, the revolutionary specifications of the

ASF1400 devices are achieved.

-400

-200

0

200

400

Massflow[sccm]

Figure 4: Differential Pressure vs. Mass Flow of

ASF1400 Device.

1.4 Adjusting the Measurement Range

To adjust the measurement range, the ASF1400

device is used in conjunction with a bypass

configuration (see Figure 5). Only a sample of the

total flow actually gets directed through the bypass

channel and the sensor system. A tube with flow

restrictor and all required connection items are

included in the Mass Flow Meter Evaluation Kit EK-

F1, also available from SENSIRION AG.

The above mentioned thermal principle requires

information about the gas type to be measured. The

ASF1400 is available for air and nitrogen. Other gas

types are available on request.

In Figure 3 the repeatability of the ASF1400 devices

is compared with the repeatability of a typical Mass

Flow Controller (MFC). It emphasizes the superior

performance of the ASF1400 device.

0.5

Specs of typical MFC

0.4

Repeatability ASF 1400

0.3

0.2

0.1

0

Figure 5: Extending the measurement range of the

ASF1400 device using a bypass configuration. Only a

sample of the total flow actually gets directed through

the bypass channel and the sensor. Shown tube with

flow restrictor is included in the EK-F1 evaluation kit.

0

100

200

300

400

Massflow[sccm]

Figure 3: Comparison of the repeatability of the

CMOSens ASF1400 device compared to a typical

Mass Flow Controller (MFC).

www.sensirion.com

November 2001 Preliminary Information

4/11

ASF1400 Bidirectional Mass Flow Meter

Since the calibrated mass flow and temperature

output values of the ASF1400 sensor have floating

point precision, the transmitted integer data is

multiplied with an SPI factor. This factor is 100.

Example: a received flow SPI value of +1234

corresponds to a flow of 12.34 sccm. Figure 7 shows

the internal setup of the SPI inter-face lines and

Figure 8 an example of cascading four ASF1400

devices using a single microcontroller.

2 Pins and Digital Interface

T

R

S

M

/

V

G

x D

x

C

I

O

D

K

D

S

O

S

I

C

S

D

N

D

Note: With each additional sensor the capacitive load

will increase, causing an increase of the output

fall/rise time and an output signal deterioration.

Figure 6: ASF1400 pin out.

GND and VDD (Power Supply)

The ASF1400 requires a voltage supply of between 7

V and 18 V. Since this voltage is internally regulated,

there are no stringent requirements as far as ripple

and stability are concerned.

2.1 RS-232 Interface

All configurations (see also Section 3) for the

ASF1400 can be set using its RS-232 interface). To

communicate with the ASF1400 via RS-232 the

following pins are required:

Figure 7: Internal ASF1400 SPI hardware.

RxD

TxD

(Receiving Data Line)

(Transmitting Data Line)

(Ground)

GND

The RS-232 of the ASF1400 is configured as follows:

Baudrate

Data Bits

Stop Bits

Parity

9600

8

1

none

Protocol

With these settings, the ASF1400 device can be

connected to any PC or PDA equipped with terminal

software.

The measurement values are provided as a signed

floating point number together with the corresponding

unit (sccm for mass flow, C for temperature). In case

of an overflow, the output shows oF.

2.2 Serial Peripheral Interface (SPI)

To make measurement data available also for smaller

systems or to cascade several ASF1400 devices, the

ASF1400 provides a uni-directional SPI interface.

The configuration of the ASF1400 (as described in

Section 3) has to be done using the RS-232 port. The

SPI interface provides the measurement data as a 24

bit signed integer, where bit 0…22 defines the value

and bit 23 the sign (0 indicates the positive, and a 1

the negative sign). The 24 bits are transmitted in 3

blocks, each consists of one byte. The MSB (bit 23) is

sent first.

Figure 8: Cascading four ASF1400 devices using the

SPI interface.

SCK (Serial Clock, Output)

The SCK synchronizes data transfer out of the device

through the MOSI line. Data on the MOSI pin is ready

after a falling edge of SCK (see Figure 9 and 10 for

details).

www.sensirion.com

November 2001 Preliminary Information

5/11

ASF1400 Bidirectional Mass Flow Meter

#13). After completion of a command, the ASF1400 returns

ok and is ready to take a new instruction. Before entering a

command, it may be necessary to clear the buffer by

means of using ↵.

/CS

(Chip Select, Input or Output)

There are two SPI modes, namely the PUSH and the GET

mode. In PUSH mode the /CS pin is controlled by the

ASF1400 device which behaves like a master. Low going

/CS announces a new data transfer (see also Section 4.3).

There is a trade-off between resolution and measurement

time. Possible settings are listed in Table 2. Choosing 12

bit results in a measurement interval of 142 ms. With the

max resolution of 15.2 bit, a new measurement is provided

every 1280 ms. For faster sampling rates refer to the

ASF1430 high speed mass flow meter device data sheet.

In GET mode the data transfer is initiated externally by

pulling /CS low. In this case, as soon as the measurement

data is ready, it appears on the MOSI pin.

MOSI (Master Out Slave In, Output)

MOSI is the serial data output of the ASF1400 device. Data

is clocked out on the rising edge SCK with MSB first. This

output goes into a high-impedance state when the device is

not selected.

Table 2: Resolution settings using the res=value command

and corresponding response times

MISO (Master In Slave Out, Not Connected)

The ASF1400 firmware only supports a uni-directional SPI

protocol. Therefore, the MISO pin should always left

unconnected.

res=

1

Resolution [bit] data interval [ms]

12.0

13.0

13.5

14.0

14.3

14.6

14.8

15.0

15.2

142

284

427

569

711

853

995

1138

1280

2

3

4

5

6

7

8

9

3 Configuration and Commands

The ASF1400 device accepts a set of commands through

its RS-232 interface (see table 3 for valid commands; for

correct settings of the RS-232 refer to Section 2.1).This

allows the user to configure the ASF1400 device. Since the

configuration is stored in the internal EEPROM, it is

maintained after power breaks.

With the exception of the stop s command, all commands

have to be terminated by the return key (↵, ASCII #10 or

Table 3: Commands of the ASF1400 device.

Command

help↵

Output

commands

version

Description

Lists all available commands

ver↵

Provides type of sensor, software, hardware and customer version

Start single measurement

get↵

go↵

Starts series of measurements

s

stop

Stops series of measurements

reset↵

res=1..9↵

res?

Resets ASF1400 device

resolution

mode

Sets resolution: 1 -> 12 bits; 9 -> 15 bits, see Table 2

Shows actual setting

mod=F | T↵

mod?

Selects Flow- (F) or Temperature mode (T)

Shows actual setting

mode

Disp=s,d

Disp?

display mode

define spi

Shows Flow (s) or Flow+Temperature (d)

Shows actual setting

*no effect in the Temerature mode

defspi=P | G↵

Sets SPI in Push- (P) or Get mode (G), see also Section 4.3

Notes:

•

Default settings are marked in bold letters

The commands are not case sensitive.

In order to send a new command to the ASF1400 make sure the ASF1400 is not in measurement mode. Issue therefore a

stop command s first. After this, any instruction can be given to the ASF1400 and a new series of measurement can be

started by go↵.

•

Due to the limited write cycles allowed for the EEPROM, excessive configuration modifications should be avoided.

www.sensirion.com

November 2001 Preliminary Information

6/11

ASF1400 Bidirectional Mass Flow Meter

4 Specifications ASF1400

4.1 Absolute Maximum Ratings

Ambient storage temperature

Ambient operating temperature

Overpressure resistance

-65°C to 150°C

0°C to 70°C

2.0 bar

4.2 Electrical Specifications

Table 3: ASF1400 DC Characteristics.

Parameter

Conditions

Min.

7

Typ.

9

Max.

18

Units

V

mA

mW

Power Supply DC

DC

VDD = 9 V, no load

VDD = 9 V, 3kΩ at RS232 output

VDD = 9 V, no load

20

Operating Current

Power Dissipation

27

180

Table 4: ASF1400 RS-232 Characteristics.

Parameter

Conditions

Min.

Typ.

Max.

Units

RS232 Output

Transmitter output loaded

±5

±9

V

Output Voltage Swing

with 3kΩ

Power-Off Output Resistance

Output Short Circuit Current

RS-232 Input

Voltage Range

Voltage Threshold

Low

300

Ω

mA

±18

-15

0.8

15

V

1.2

1.7

0.5

5

V

High

2.4

1.0

7

Hysteresis

Resistance

0.2

3

kΩ

www.sensirion.com

November 2001 Preliminary Information

7/11

ASF1400 Bidirectional Mass Flow Meter

Table 5: ASF1400 SPI Characteristics (refer to Figure 9 for a timing diagram).

Symbol Parameter

Conditions

not connected

Rl=100kΩ

Vdd = 5V

Min.

0

Typ.

0.2

4.9

0.2

4.45

-60

0.3

87

Max.

0.4

5

Units

V

Vol

Voh

Vol

Voh

Ioh

Iol

Output Low Voltage

Output High Voltage

Output Low Voltage

Output High Voltage

Output High Current

Output Low Current

SCK Frequency

Output Rise Time

Output Fall Time

Output Rise Time

Output Fall Time

Clock High Time

Clock Low Time

/CS Setup Time

Send Time

4.8

0

V

0.5

V

2.4

µA

mA

kHz

ns

Vdd = 5V

fop

tro

not connected

Rl=100kΩ

40

tfo

26

ns

tro

42

ns

tfo

30

ns

Rl=100kΩ

tclh

tcll

5.70

5.80

µs

tcss

tst

15.0

27.0

930

/CS

SCK

MOS

I

Figure 9: Timing Diagram of the ASF1400 SPI Interface.

www.sensirion.com

November 2001 Preliminary Information

8/11

ASF1400 Bidirectional Mass Flow Meter

4.3 SPI Push-Mode Detailed Description

The subsequent scope diagrams further describe the ASF1400 device SPI mode data access protocol in PUSH

mode.

1 = SCK

2 = /CS

Serial clock output

Chip select (Push-Mode)

Serial data output

3 = MOSI

Complete read cycle (three bytes)

Close up of one byte

First byte

Third byte

Figure 10: Sample for SPI read cycle of the ASF1400 in Push Mode.

www.sensirion.com

November 2001 Preliminary Information

9/11

ASF1400 Bidirectional Mass Flow Meter

5 Physical Dimensions and Mounting Information

The ASF1400 is mounted in chemically inert PBT housing.

The rugged package has been designed to withstand

overpressures of up to 2 bars. Higher pressure packages of

up to 10 bars are available on request.

Physical dimensions and mounting information are

provided in Figure 11 and Table 6.

holes for ∅ 3 mm screws

8

nozzles for ∅ 6 mm

rubber hose.

1

h

Table 6: Physical Dimensions of the ASF1400 device.

Length

Width

L

45.0 mm

40.0 mm

15.5 mm

25.2 mm

5.0 mm

W

h

Height

Distance

Diameter

Pitch

D

d

s

2.54 mm

20.6 mm

29.1 mm

10.0 mm

Pitch

H

G

N

Pitch

Holes for

PT^screws

(∅ 2.2 mm, screw in

not more than 4.4 mm)

Figure 11: Physical dimensions and mounting information of the ASF1400.

6 Ordering Information

For small ordering quantities the ASP1400 sensor can be ordered directly at Farnell on http://www.farnell.com. Farnell is a

worldwide distributor of electrical, electronic and industrial component products.

When ordering ASF1400 series devices at SENSIRION please refer to the following part numbers. For the latest product

information access SENSIRION’s website on http://www.sensirion.com

Calibrated for Gas Type

Nitrogen

Other gas types on request

Range

± 400 sccm

Packaging

2 bar

Part Number

1-100011

-

Notes:

ꢀ

Packages to sustain common mode pressures of 10 bars are available on request.

Special electrical interfaces such as 4-20 mA output or others are available on request.

For faster response times refer to the ASF1430 data sheet.

A evaluation kit including ASF1400 devices, evaluation software and other accessories such a bypass, rubber hose and

cables can be ordered. For detailed information check out the description of the Mass Flow Meter Evaluation Kit EK-F1 on

http://www.sensirion.com

www.sensirion.com

November 2001 Preliminary Information

10/11

ASF1400 Bidirectional Mass Flow Meter

IMPORTANT NOTICES

The warranty for each SENSIRION AG product

comes in the form of a written warranty which governs

sale and use of such product. Such warranty is

contained in the printed terms and conditions under

which such product is sold, or in a separate written

warranty supplied with the product. Please refer to

such written warranty with respect to its applicability

to certain applications of such product.

Flow product specifications and/or information in this

document and to improve reliability, functions and

design.

SENSIRION AG assumes no responsibility or liability

for any use of SENSIRION ASF1400 product.

Application examples and alternative uses of the

SENSIRION ASF1400 are for illustration purposes

only and SENSIRION AG makes no representation or

warranty that such applications shall be suitable for

the use specified.

These products may be subject to restrictions on use.

Please contact SENSIRION AG for a list of the

current additional restrictions on these products. By

purchasing these products, the purchaser of these

products agrees to comply with such restrictions.

Please contact SENSIRION AG for clarification of any

restrictions described herein.

SPI is a trademark of Motorola. LabView is a

trademark of National Instruments.

reserved.

SENSIRION AG reserves the right, without further

notice, to change the SENSIRION ASF1400 Mass

FCC and CE Statement

The ASF1400 product has been tested and found to

comply with the limits for a Class B digital device,

pursuant to part 15 of the FCC Rules (FCC CFR 47).

These limits are designed to provide reasonable

protection against harmful interference in a residential

installation. This equipment generates, uses and can

radiate radio frequency energy and, if not installed

and used in accordance with the instructions, may

cause harmful interference to radio communications.

However, there is no guarantee that interference will

not occur in a particular installation. If this equipment

does cause harmful interference to radio or television

reception, which can be determined by turning the

equipment off and on, the user is encouraged to try to

correct the interference by one of more of the

following measures:

•

Increase the separation between the

equipment and the receiver

Connect the equipment into an outlet on a

circuit different from that to which the

receiver is connected.

•

Consult a dealer or an experienced radio/TV

technician for help.

The ASF1400 device fully complies with norm EN

50081-2 (Emission Test Series) as well as EN 50082-

2 (Immunity Test Series).

•

Reorient or relocate the receiving antenna.

Headquarters and Sales Office

SENSIRION AG

Eggbühlstr. 14

P.O. Box

Phone: + 41 (0)1 306 40 00

Fax:

+ 41 (0)1 306 40 30

e-mail: info@sensirion.com

http://www.sensirion.com/

CH-8052 Zürich

Switzerland

www.sensirion.com

November 2001 Preliminary Information

11/11


型号：	1-100011
厂家：	ETC
描述：	SENSOR MASS FLOW 传感器质量流量\n 传感器
文件：	总11页 (文件大小：614K)
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