Thermal mass flow meter

A thermal mass flow meter comprising:

• a flow conduit;
• a flow-splitting substrate member extending transversely across a portion of said conduit and containing active flow sensors;
• means for providing passive by-pass fluid flow paths in said conduit;
• said substrate member including:
• means for forming an elongated channel extending from one edge of the substrate member to an opposite edge of the substrate member;
• means for forming a first temperature-sensing member integral with said substrate member extending transversely across said channel;
• a second temperature-sensing member on said substrate member;
• and
• means in the channel for differentially heating at least one of said first and second temperature-sensing members to indicate the flow rate of said fluid by comparison with output signals from said first and second temperature sensing members.

A thermal mass flow meter for fluids comprising:

• a substrate;
• a continuous elongated flow channel having side walls and a bottom extending on a surface of said substrate from one edge of the substrate to an opposed edge of the substrate;
• a membrane having a top side and under side and being integral with said substrate, said membrane extending transversely across at least a portion of said channel and spaced from said channel bottom such that fluid passes through said channel transversely of and parallel to both the top side and under side of said membrane;
• a first temperature sensor on said membrane;
• a second temperature sensor on said substrate spaced from said first temperature sensor;
• and
• means for heating at least one of said first and second temperature sensors to provide a temperature difference between said first temperature sensor and said second temperature sensor indicative of mass fluid flow.

A thermal mass flow meter for fluids comprising a substrate;

• an elongated channel extending on a surface of said substrate for conveying a fluid, said substrate having at least two integral members spaced from each other and extending transversely across at least a portion of said channel;
• means for forming a temperature sensor on said of said members;
• means in said channel for heating said fluid to provide a temperature difference between said sensors when fluid is being conveyed;
• and
• wherein said substrate comprises a first element including said channel and said integral members and a second element having an elongated channel corresponding to said channel on said first element said elements being bonded together whereby said integral members divide a flow path formed by said corresponding channels.