Product Specification

LMM-H04 Mass Air Flow Sensor Product Description
LMM-H04 is a thermodynamic sensing element for the unidirectional measurement of mass air flow in a well defined channel. It is intended for applications with high reliability requirements such as automotive, medical or industrial gas flow applications. Mounted directly within the flowing media the LMM-H04 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-H04 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-H04 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.

LMM-H04 Mass Air Flow Sensor Features
? Highly reliable and long term stability
? Fast reaction time
? Can be adapted to various flow channel geometries
? Can be used for almost all kinds of gases and volatile substances

LMM-H04 Mass Air Flow Sensor Applications
? Engine Control
? Industrial gas flow measurement
? Leak detection in pressurized air systems
? Spirometer

LMM-H04 Mass Air Flow Sensor Absolute Maximum Ratings