초록 ▼

A mass flowmeter of the thermal type provided with a flow sensor with a flow tube through which a fluid can flow during operation, with a temperature sensor in an upstream position (A) and a heater (H) in a downstream position (B), and power control means and temperature measuring means for keeping

A mass flowmeter of the thermal type provided with a flow sensor with a flow tube through which a fluid can flow during operation, with a temperature sensor in an upstream position (A) and a heater (H) in a downstream position (B), and power control means and temperature measuring means for keeping the temperature difference between A and B at a predetermined constant value. Between A and B, the flowmeter is provided with means for preventing the temperature at A from rising owing to thermal conduction from B to A via the tube in the case of no flow or a weak flow.

대표청구항 ▼

The invention claimed is: 1. A mass flowmeter of the thermal type provided with a flow sensor with a U-shaped tube having two ends through which a fluid can flow during operation, with a first upstream position A and a second downstream position B, a temperature sensor in the first upstream positio

The invention claimed is: 1. A mass flowmeter of the thermal type provided with a flow sensor with a U-shaped tube having two ends through which a fluid can flow during operation, with a first upstream position A and a second downstream position B, a temperature sensor in the first upstream position A and a heater H in the second downstream position B, wherein the flowmeter is provided with a metal base having two bores, the ends of the U-shaped tube passing through the two bores in the metal base, a thermal drain directly connecting the tube in a location on the tube between the positions A and B to the metal base. 2. A mass flowmeter as claimed in claim 1, wherein the thermal drain is a copper strip. 3. A mass flowmeter as claimed in claim 1, wherein the thermal drain has a better thermal conductivity than the tube. 4. A mass flowmeter as claimed in claim 1, wherein the heater H is an electrical coiling of temperature sensitive resistance wire wound on the tube and also serves as a temperature sensor. 5. A mass flowmeter as claimed in claim 1, wherein the thermal drain comprises a Peltier element provided on the tube between the positions A and B. 6. A mass flowmeter of the thermal type provided with a flow sensor with a U-shaped tube having two ends through which a fluid can flow during operation, with a first upstream position A and a second downstream position B, a temperature sensor in the first upstream position A and a heater H in the second downstream position B, wherein the flowmeter is provided with a metal base having two bores, a housing being placed on the base which encloses the U-shaped tube, the ends of the U-shaped tube passing through the two bores in the metal base, a thermal drain directly connecting the housing to a location on the tube between A and B. 7. A mass flowmeter as claimed in claim 6, wherein the thermal drain is a copper strip. 8. A mass flowmeter as claimed in claim 6, wherein thermal drain has a better thermal conductivity than the tube. 9. A mass flowmeter as claimed in claim 6, wherein the heater H is an electrical coiling of temperature sensitive resistance wire wound on the tube and also serves as a temperature sensor. 10. A mass flowmeter as claimed in claim 6, wherein the thermal drain comprises a Peltier element provided on the tube between the positions A and B. 11. A mass flowmeter of the thermal type provided with a flow sensor with a tube having two ends through which a fluid can flow during operation, with a first upstream position A and a second downstream position B, a temperature sensor in the first upstream position A and a heater H in the second downstream position B, wherein the tube is a straight tube having two ends which are thermally floating, a thermal drain being directly connected to the tube in a location between the positions A and B. 12. A mass flowmeter as claimed in claim 11, wherein the thermal drain is a copper strip. 13. A mass flowmeter as claimed in claim 11, wherein the thermal drain has a better thermal conductivity than the tube. 14. A mass flowmeter as claimed in claim 11, wherein the heater H has an electrical coiling of temperature sensitive resistance wire wound on the tube and also serves as a temperature sensor. 15. A mass flowmeter claimed in claim 11, wherein the thermal drain comprises a Peltier element provided on the tube between the positions A and B.