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www.sensirion.com sensirion ag, laubisrtistrasse 50, ch-8712 st?fa zh, switzerland, phone: +41 44 306 40 00, fax: +41 44 306 4 0 30 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 & tem perature compensated _ rs-232 and 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. all measurement data is fully calibrated and temperature compensated by means of an internal microcontroller. 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). the asf1400 requires a supply voltage of 7?18vdc and provides an rs-232 compliant electrical interface. version 2.2 / november mass flow voltage regulator micro controller rs232 line driver/ receiver eeprom gnd vdd /cs mosi miso sck rxd txd mass flow asf1400 mass flow meter spi interface rs232 interface power supply cmosens ? sensor chip thermal sensor amplifier adc no longer supported figure 1: block diagram asf1400 mass flow sensor with cmosens ? technology.
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 of 3 mm 3 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. 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. the rs-232 interface allows you to directly connect the asf1400 device to a pc or pda using standard terminal software. if a special interface such as 4-20 ma current output or other is required contact sensirion for a customer specific solution. 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. 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?). www.sensirion.com version 2.2 2/9
asf1400 bidirectional mass flow meter 1 mass flow sensor performance table 1: overview of asf1400 gas sensor performance 1 parameter condition minimum typical maximu m units flow sensor direct measurement -400 400 sccm ( ) 2 using proposed bypass tube (2 ) 3 -100 100 liter/min ( ) 4 dynamic range customized bypass tube unlimited unlimited resolution 400 sccm flow 0.09 sccm < 10 sccm flow 0.01 sccm lowest detectable flow < 10 sccm flow 0.015 (4) sccm pressure drop 400 sccm, p abs. = 1 bar 120 pa ( ) 5 repeatability 0.0025 % fs ( ) 6 0.025 % m.v. 0?5 % of full scale 0.05 % fs ( ) 7 accuracy 23 c 5?100 % of full scale 1 % m.v. ( ) 7 offset 23c < 0.005 < 0.02 % fs overpressure resistance 2 bar ( ) 8 depends on resolution setting 142 1280 ms response time ( ) 9 (see section 3, table 2) operating temperature 0 70 c zero < 0.005 % fs / c ambient temperature coefficient span < 0.08 % measured value / c position sensitivity p =1 bar, small nitrogen flow 0.008 % fs abs temperature sensor measures temperature inside the sensor, but not of the surrounding air (10 ) 10 dynamic range 0 70 c resolution 0.1 c accuracy 3 2 c 1 all data apply for calibration conditions (20c, 1013 mbar) unless otherwise noted. 2 1 sccm = 1 cm 3 /min at 0c and 1013mbar pressure (1sccm = 0.001 norm liter) 3 using bypass tube included in sensirion?s mass flow meter evaluation kit ek-f1 4 1 liter/min = 1000 sccm 5 1 bar = 100 000 pa = 0.9869 atm = 401.9 inch h 2 o = 14.5 psi 6 error = % of full scale (fs) or % of measured value, whichever is bigger. 7 better calibration available for high volume oem on r equest. allow the sensor to warm up for best results. 8 for higher overpressure resistance vers ions please check the em1 product page. 9 for faster response times please check out the ASF1430 high speed mass flow meter data sheet the sensor warms up by about 7c (depending on supply voltage and ventilation). 10 www.sensirion.com version 2.2 3/9
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 -500 -250 0 250 500 -500 -250 0 250 500 mass flow [sccm] asf1400 output [sccm] 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). - 400 - 200 0 200 400 massflow [sccm] - 150 - 100 -50 0 50 100 150 differential pressure [pa] figure 2: asf1400 transfer characteristics. 1.2 sensor principle and gas types 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. 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. flow restrictor asf 1400 0 100 200 300 400 massflo w [ sccm ] 0 0.1 0.2 0.3 0.4 0.5 repeatability [% of measured v alue] 200 specs of typical mfc repeatability asf 1400 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. figure 3: comparison of the repeatability of the cmosens ? asf1400 device compared to a typical mass flow controller (mfc). www.sensirion.com version 2.2 4/9
asf1400 bidirectional mass flow meter 2 pins and digital interface 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.

2.3 serial peripheral interface (spi) the in earlier versions available spi interface is due to changes in electronic components no longer supported. figure 6: asf1400 pin out. 3 configuration and commands gnd and vdd (power supply) 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. 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 connector with the exception of the stop s command, all commands have to be terminated by the return key ( ?, ascii #10 or #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 ? . you need an edac 395-010-520-102 connector to connect the sensor. please check the edac homepage for details (www.edac.net). alternatively the avx 00 6338 020 000 04 0 or avx 00 6338 020 000 04 2 connectors can be used to connect the asp1400 as well. (see www.farnell.com, order codes 635789 or 635730). 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 mete r device data sheet. 2.2 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: rxd (receiving data line) table 2: resolution settings using the res= value command and correspondi ng response times txd (transmitting data line) gnd (ground) the rs-232 of the asf1400 is configured as follows: baudrate 9600 data bits 8 stop bits 1 parity none protocol none with these settings, the asf1400 device can be connected to any pc or pda equipped with terminal software. res= resolution [bit] data interval [ms] 1 12.0 142 2 13.0 284 3 13.5 427 4 14.0 569 5 14.3 711 6 14.6 853 7 14.8 995 8 15.0 1138 9 15.2 1280 table 3: commands of the asf1400 device. command output description help ? commands lists all available commands www.sensirion.com version 2.2 5/9
asf1400 bidirectional mass flow meter ver ? version provides type of sensor, so ftware, hardware and customer version get ? start single measurement go? starts series of measurements s stop stops series of measurements reset ? resets asf1400 device res=1.. 9 ? resolution sets resolution: 1 -> 12 bits; 9 -> 15 bits, see table 2 res? resolution shows actual setting mod= f | t ? mode selects flow- (f) or temperature mode (t) mod? mode shows actual setting disp= s ,d display mode shows flow (s) or flow+temperature (d) *no effect in the temerature mode disp? display mode shows actual setting defspi= p | g ? define spi 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 cycl es allowed for the eeprom, excessive conf iguration modificati ons should be avoided. 4 specifications asf1400 4.1 absolute maximum ratings ambient storage temperature -65c to 150c ambient operating temperature 0c to 70c overpressure resistance 2.0 bar 4.2 electrical specifications table 3: asf1400 dc characteristics. parameter conditions min. typ. max. units power supply dc dc 7 9 18 v vdd = 9 v, no load 20 ma operating current 27 ma vdd = 9 v, 3k at rs232 output power dissipation vdd = 9 v, no load 180 mw table 4: asf1400 rs-232 characteristics. parameter conditions min. typ. max. units rs232 output transmitter output loaded with 3k 5 9 v output voltage swing power-off output resistance 300 output short circuit current 18 ma rs-232 input voltage range -15 15 v voltage threshold low 0.8 1.2 v high 1.7 2.4 v hysteresis 0.2 0.5 1.0 v resistance 3 5 7 k www.sensirion.com version 2.2 6/9
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.

1 8 ! " # holes for ? 3 mm screws nozzles for ? 6 mm rubber hose. h table 6: physical dimensions of the asf1400 device. length l 45.0 mm width w 40.0 mm height h 15.5 mm distance d 25.2 mm diameter d 5.0 mm pitch s 2.54 mm pitch h 20.6 mm pitch g 29.1 mm pitch n 10.0 mm figure 11: physical dimensions and mounting information of the asf1400. holes for ? screws pt ( ? 2.2 mm, screw in not more than 4.4 mm ) 6 ordering information for small ordering quantities the asf1400 sensor can be ordered directly at farnell on http://www.farnell.com . farnell is a worldwide distributor of electrical, el ectronic and industrial component products. when ordering asf1400 series devices at sensirion please refer to the following part numbers. for the latest product informatio n access sensirion?s website on http://www.sensirion.com calibrated for gas type range packaging type air 400 sccm 2 bar asf1400 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 version 2.2 7/9
asf1400 bidirectional mass flow meter important notices ? the defective product shall be returned to sensirion?s factory at the buyer?s expense; and 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 and authorized use. before installing, handling, using or servicing this product, please consult the data sheet and application notes. failu re to comply with these instructions could result in death or serious injury. ? 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. if the buyer shall purcha se 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. 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 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. 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. see application note ?esd, latchup and emc? for more information. sensirion reserves the righ t, 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. 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: copyright 2001-2008, sensirion. ? cmosens is a trademark of sensirion ? all rights reserved rohs and weee statement the sdp6x0 family complies with requirements of the following directives: ? notice in writing describing the defects shall be given to sensirion within fourteen (14) days after their appearance; ? eu directive 2002/96/ec on waste electrical and electronic equipment ( weee ), oj13.02.2003; esp. its article 6 (1) with annex ii. ? such defects shall be found, to sensirion?s reasonable satisfaction, to have arisen from sensirion?s faulty design, material, or workmanship; ? 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 2.2 8/9
asf1400 bidirectional mass flow meter revision history table 1: revision history date version page(s) changes dec. 2001 preliminary all first public release may 2005 v2.1 all specifications, typos, various small modifications november 2008 v2.2 all spi interface no longer supported ,overpressure resistance changed, new iso-logo, sales office information, introduction of revision history, new disclaimer, rohs compliance headquarters and sales office sensirion ag phone: + 41 44 306 40 00 laubisruetistrasse 50 fax: + 41 44 306 40 30 ch-8712 staefa zh e-mail: info@sensirion.com switzerland web: www.sensirion.com sales office usa (for north american customers only) sensirion inc phone: +1 805-409 4900 westlake pl. ctr. i, suite 204 fax: +1 805-435 0467 2801 townsgate road e-mail: michael.karst@sensirion.com westlake village, ca 91361 web: www.sensirion.com usa sales office korea (for korean customers only) sensirion korea co. ltd. phone: +82 31-440-9925~27 #1414, anyang construction twr b/d fax: +82 31-440-9927 1112-1, bisan-dong, anyang-city e-mail: info@sensirion.co.kr gyeonggi-province, web: www.sensirion.co.kr south korea sales office japan (for japanese customers only) sensirion japan co. ltd tel : +81 3-3444-4940 representative director: keiichi hasegawa fax: +81 3-3444-4939 shinagawa station bldg. 7f, 4-23-5, tak anawa, e-mail: info@sensirion.co.jp minato-ku, tokyo, japan web: www.sensirion.co.jp www.sensirion.com version 2.2 9/9

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