Model LMM-H03 Mass Air Flow Sensor Hot Film Anemometer Component Highly reliable and long term stable Bi-directional airflow measurement Fast reaction time Manufactured according ISO TS16949 Can be adapted to various flow channel geometries Can be used for almost all kind of gases and volatile substances DESCRIPTION LMM-H03 is a thermodynamic sensing element for the bidirectional measurement of mass air flow in a well defined channel. It is dedicated for applications with high reliability requirements such as medical or industrial gas flow applications. Mounted directly within the flowing media the LMM-H03 is sensitive against the heat transfer on a micrometer scale. This heat transfer is detected by a micro-machined silicon device which is mounted on ceramic substrate defining the geometry of the sensing element. The functional principle of the LMM-H03 is a hot film anemometer, which is the thin film version of the hot wire anemometer. A thin film heating element (heater) is heated to a defined temperature difference with respect to the air. At zero flow there is heat dissipation due to the thermal conductivity of the air. With applied flow the heat dissipation increases steadily with the flow rate. The sensing element can be operated at Constant Power and Constant Voltage mode. However, it is recommended to operate LMM-H03 in the described Constant Temperature Difference (CTD) mode. In the CTD mode the electronics detects any change of the thermal equilibrium very quickly and compensates it by adjusting the power settings through the heaters. This allows a very reliable mass flow measurement with a very short time constant which is in the order of milliseconds. FEATURES APPLICATIONS Highly reliable and long term stable Fast reaction time Can be adapted to various flow channel geometries Can be used for almost all kind of gases and volatile substances Model LMM-H03 Rev3 Industrial gas flow measurement Leakdetection in pressurized air systems Spirometer www.meas-spec.com 1/5 28 August 2012 Model LMM-H03 Mass Air Flow Sensor ABSOLUTE MAXIMUM RATINGS Parameter Max. Heater Overtemperature Operating Temperature Storage Temperature Storage Temperature Min Typical 100 Max <120 Unit K -40 +25 +125 C -40 +25 +125 C +10 +25 +40 C Description approx. RH(Tamb)x1.5 after bonding, with protected bond pads after bonding, with protected bond pads before bonding, 3 month MECHANICAL DIMENSIONS Figure 1: Mechanical dimensions and connections of LMM-H03 The sensor membrane has a thickness of about ~2 m. Therefore it should not be exposed to any mechanical stress. One has to take care of a filter unit around the measurement device. High speed particles coming direct to the surface of the membrane can result in damages or shortage of the life time. The ventilation holes shall be kept open to release air pressure built up due to heating. Parameter Package Type Length Width Height Ceramics Height Ceramics+Metal max. overall Height Bond Pad Size Bond Pad Material Model LMM-H03 Rev3 Typical Hybride 23.000.2 mm 10.150.2 mm 0.630.15 mm 1.100.2 mm < 1.8 mm 1.50.5 mm2 AgPt Condition 25C 25C 25C 25C 25C, at Glob Top position 25C bondable with 150m Al-wire www.meas-spec.com 2/5 28 August 2012 Model LMM-H03 Mass Air Flow Sensor ELECTRICAL PROPERTIES Parameter RATS1* RHeater1 RHeater2 RATS2* Temperatur Coefficients RATS and RHeater TCR Match * Typical 1700400 45.05.0 45.05.0 1700400 Condition Pad 1+2, 25C Pad 3+4, 25C Pad 5+6, 25C Pad 7+8, 25C 6000500 ppm/K 0C 100C <100 ppm/K 0C 100C ATS = Ambient Temperature Sensor APPLICATION EXAMPLE One application of the LMM-H03 is to measure the amount of air coming into an engine. The actual mass air flow sensor module consists of a flow channel and a measurement channel, the so called Venturi channel. The measurement channel with the LMM-H03 should be placed in the center of the flow channel because at this place the flow is almost laminar and the flow velocity reaches its maximum. The cross sections of both channels can be adjusted to the amount of air which is supposed to be measured. For reproducible measurement results it is strictly required to avoid any turbulence at the surface of the sensing element. Figure 2: Flow channel of application example of a mass air flow sensor Model LMM-H03 Rev3 www.meas-spec.com 3/5 28 August 2012 Model LMM-H03 Mass Air Flow Sensor Figure 3: Above is shown an example of a measurement electronics using a Wheatstone-bridge. The resistors RAx and RBx need to be trimmed to operate the heater at a defined over-temperature NOTE: This drawing shows only the basic functionality. This is not a ready to use circuit diagram! As an example the graphs below show the heater power as a function of flow velocity. The configuration used the following parameters: Flow Channel : Measurement Channel: o Height: o Width: o Length: 55-70 mm 1-2 mm 10-15 mm >20xHeight (bidirectional) 200 Heater Power [mW] 150 100 50 0 0 10 20 30 40 50 60 Flow Velocity [m/s] Figure 3: Example of a Power-Flow-Response of the LMM-H03 With a given electronics and measurement channel the measurement range can be easily adjusted by modifying the size of the flow channel. For higher or lower flow ranges the flow channel needs to be made larger or smaller, respectively. Model LMM-H03 Rev3 www.meas-spec.com 4/5 28 August 2012 Model LMM-H03 Mass Air Flow Sensor ORDERING INFORMATION Part Number Part Description G-MAFCO-005 LMM-H03 TECHNICAL CONTACT INFORMATION NORTH AMERICA Measurement Specialties, Inc. 1000 Lucas Way Hampton, VA 23666 Tel: 1-800-745-8008 Fax: 1-757-766-4297 Email: sales@meas-spec.com Web: www.meas-spec.com EUROPE Europe MEAS Deutschland GmbH Hauert 13, D-44227 Dortmund, Germany Phone: +49-(0)231-9740-0 Fax: +49-(0)231-9740-20 Email: info.de@meas-spec.com Web: www.meas-spec.com ASIA Measurement Specialties China Ltd. No. 26, Langshan Road, Shenzhen High-tech Park (North) Nanshan District, Shenzhen, China 518057 Phone: +86-755-33305088 Fax: +86-755-33305099 Email: info.cn@meas-spec.com Web: www.meas-spec.com The information in this sheet has been carefully reviewed and is believed to be accurate; however, no responsibility is assumed for inaccuracies. Furthermore, this information does not convey to the purchaser of such devices any license under the patent rights to the manufacturer. Measurement Specialties, Inc. reserves the right to make changes without further notice to any product herein. Measurement Specialties, Inc. makes no warranty, representation or guarantee regarding the suitability of its product for any particular purpose, nor does Measurement Specialties, Inc. assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Typical parameters can and do vary in different applications. All operating parameters must be validated for each customer application by customer's technical experts. Measurement Specialties, Inc. does not convey any license under its patent rights nor the rights of others. Model LMM-H03 Rev3 www.meas-spec.com 5/5 28 August 2012 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: TE Connectivity: G-MAFCO-005