Single-probe mass flow meters

Abstract

Microprocessor-based thermal dispersion mass flow meters (i.e., thermal anemometers) are described that use temperature sensing elements in its flow sensor probe(s) in addition to the two elements commonly used. Such systems allow for automatically managing changes in gas selection, gas temperature, gas pressure, and outside temperature. One mass flow meter described has a flow sensor with four temperature sensing elements, wherein one pair is provided in a temperature sensor probe and another pair in a velocity sensor probe. Another variation operates without a separate temperature sensor probe and integrates all function into a single three-sensor probe. Such a device may also be used in conjunction with a one- or two-sensor temperature probe.

What is claimed is: 
     
         1 . A mass flow meter apparatus for immersion in fluid flow comprising:
 a probe including a Resistance Temperature Detector (RTD) having a heated length and electrically coupled to a proximal end of the probe;   a second temperature sensor adjacent to a proximal end of the heated length, an active region of the second temperature sensor located a distance from the heated length equal to or less than about three times a diameter of the velocity sensor probe, and a third temperature sensor to determine fluid flow temperature, wherein the apparatus includes no separate temperature sensor probe.   
     
     
         2 . The apparatus of  claim 1 , wherein the third temperature sensor is located distal to the heated length. 
     
     
         3 . The apparatus of  claim 2 , wherein the third sensor is located a distance equal to or greater than a diameter of the probe from the heated length. 
     
     
         4 . The apparatus of  claim 3 , wherein the third temperature sensor is located within about two and about three probe diameters distance from the heated length. 
     
     
         5 . The apparatus of  claim 2 , wherein a surface of the third temperature sensor is located within about 0.1 inches of the heated length. 
     
     
         6 . The apparatus of  claim 1 , wherein a surface of the second temperature sensor is located within about 0.1 inches of the heated length. 
     
     
         7 . The apparatus of  claim 1 , further comprising a computer processor for outputting mass velocity measurements in real time. 
     
     
         8 . The apparatus of  claim 7 , further comprising a transmitter for wireless communication of the measurements. 
     
     
         9 . The apparatus of  claim 1 , wherein the RTD comprises a platinum wire winding, the winding set upon a non-conductive spacer. 
     
     
         10 . The apparatus of  claim 9 , wherein the spacer is adapted at a proximal end to receive the second temperature sensor therein. 
     
     
         11 . The apparatus of  claim 9 , wherein the spacer is adapted at a distal end to receive the third temperature sensor therein. 
     
     
         12 . The apparatus of  claim 11 , wherein the spacer is further adapted at a proximal end of the spacer to receive the second temperature sensor therein. 
     
     
         13 . The apparatus of  claim 11 , wherein at least one of the second and third temperature sensors comprises a thin-film RTD. 
     
     
         14 . The apparatus of  claim 11 , wherein the spacer includes four lumen with two lumen receiving electrical leads for the heated sensor and two lumen receiving electrical leads for the third temperature sensor. 
     
     
         15 . The apparatus of  claim 1 , wherein at least one of the second and third temperature sensors comprises a thin-film RTD.