Flow sensor

A flow sensor, comprising:

• a thin film heater;
• a pair of thin film heat sensors;
• a semiconductor body supporting the heater and sensors with at least a major portion of the heater and sensors held out of contact with the body by thin film dielectric and with the sensors disposed on opposite sides of the heater;
• means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature;
• the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient;
• and
• the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

A flow sensor, comprising:

• a thin film heater;
• a pair of thin film sensors;
• a semiconductor body with a depression therein;
• thin film means connecting the heater and the sensors to the body and bridging the depression so that at least a major portion of the heater and the sensors are out of contact with the body and with the sensors disposed on opposite sides of the heater;
• means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature;
• the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient;
• and
• the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

A flow sensor comprising:

• a thin film heater encapsulated in thin film dielectric;
• a pair of thin film sensors encapsulated in thin film dielectric, the sensors being disposed on opposite sides of the heater;
• a semiconductor body with a depression therein;
• the encapsulated heater and sensors forming at least one thin film member bridged across the depression so that at least a major portion of the heater and the sensors are out of contact with the semiconductor body;
• means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature;
• the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient;
• and
• the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

A flow sensor comprising:

• a semiconductor body having a depression formed into a first surface of the body;
• a thin film heater encapsulated in thin film dielectric;
• a pair of thin film sensors encapsulated in thin film dielectric, the thin film sensors being disposed on opposite sides of the heater;
• the encapsulated heater and sensors forming at least one thin film member, the at least one thin film member being attached to the first surface at least at one location in order to suspend at least a major portion of the heater and sensors over the depression;
• means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature;
• the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient;
• and
• the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

A flow sensor, comprising:

• a thin film heater;
• a pair of thin film sensors;
• a semiconductor body with a depression therein, the semiconductor body comprising (100) silicon having a (100) plane and [110] directions;
• the heater and sensors lying in a plane substantially parallel to the (100) plane;
• thin film means connecting the heater and the sensors to the body and bridging the depression so that at least a major portion of the heater and the sensors are out of contact with the body and with the sensors disposed on opposite sides of the heater, the means connecting the heater and the sensors to the body having a configuration oriented at a non-zero angle to the [110] direction;
• means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature;
• the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient;
• and
• the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

A flow sensor comprising:

• a thin film heater encapsulated in thin film dielectric;
• a pair of thin film sensors encapsulated in thin film dielectric, the sensors being disposed on opposite sides of the heater;
• a semiconductor body with a depression therein;
• and
• the encapsulated heater and sensors forming two thin film members bridged across the depression so that at least a major portion of the heater and the sensors are out of contact with the semiconductor body, approximately one half of the heater and approximately one half of each sensor being located on each member.

A flow sensor comprising:

• a semiconductor body having a depression formed into a first surface of the body;
• a thin film heater encapsulated in thin film dielectric;
• a pair of thin film sensors encapsulated in thin film dielectric, the thin film sensors being disposed on opposite sides of the heater;
• and
• the encapsulated heater and sensors forming two thin film members attached to the first surface at least at one location in order to suspend at least a major portion of the heater and the sensors over the depression, approximately one half of the heater and approximately one half of each sensor being located on each member.