Model LMM-H03 Mass Air Flow Sensor
Model LMM-H03 Rev3 www.meas-spec.com 28 August 2012
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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 Industrial gas flow measurement
Fast reaction time Leakdetection in pressurized air systems
Can be adapted to various flow channel geometries Spirometer
Can be used for almost all kind of gases and volatile
substances
Model LMM-H03 Mass Air Flow Sensor
Model LMM-H03 Rev3 www.meas-spec.com 28 August 2012
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ABSOLUTE MAXIMUM RATINGS
Parameter
Min
Typical
Max
Unit
Description
Max. Heater Overtemperature 100 <120 K approx. RH(Tamb)×1.5
Operating Temperature -40 +25 +125 °C after bonding, with
protected bond pads
Storage Temperature -40 +25 +125 °C after bonding, with
protected bond pads
Storage Temperature +10 +25 +40 °C before bonding, 3 month
MECHANICAL DIMENSIONS
Figure 1: Mechanical dimensions and connections of LMM-H03
The sensor membrane has a thickness of about ~2 µm. 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 Typical Condition
Package Type Hybride 25°C
Length 23.000.2 mm 25°C
Width 10.150.2 mm 25°C
Height Ceramics 0.630.15 mm 25°C
Height Ceramics+Metal 1.100.2 mm 25°C, at Glob Top position
max. overall Height < 1.8 mm 25°C
Bond Pad Size 1.50.5 mm2 bondable with 150µm Al-wire
Bond Pad Material AgPt
Model LMM-H03 Mass Air Flow Sensor
Model LMM-H03 Rev3 www.meas-spec.com 28 August 2012
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ELECTRICAL PROPERTIES
Parameter Typical Condition
RATS1
*
1700400 Pad 1+2, 25°C
RHeater1 45.05.0 Pad 3+4, 25°C
RHeater2 45.05.0 Pad 5+6, 25°C
RATS2
*
1700400 Pad 7+8, 25°C
Temperatur Coefficients
RATS and RHeater 6000500 ppm/K 0°C 100°C
TCR Match <100 ppm/K 0°C 100°C
*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 Mass Air Flow Sensor
Model LMM-H03 Rev3 www.meas-spec.com 28 August 2012
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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 : 55-70 mm
Measurement Channel:
oHeight: 1-2 mm
oWidth: 10-15 mm
oLength: >20×Height (bidirectional)
0
50
100
150
200
0 10 20 30 40 50 60
Flow Velocity [m/s]
Heater Power [mW]
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 Mass Air Flow Sensor
Model LMM-H03 Rev3 www.meas-spec.com 28 August 2012
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ORDERING INFORMATION
Part Number G-MAFCO-005
Part Description LMM-H03
TECHNICAL CONTACT INFORMATION
NORTH AMERICA EUROPE ASIA
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
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
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.
