Software and methods for mass flow meter computation

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 computer readable medium having stored thereon instructions, which when executed cause one or more processors to:
 receive input signals corresponding to two or more temperature measurements from a velocity probe including a heated sensor and a secondary temperature sensor spaced apart from the heated sensor by a distance no greater than three times a diameter of the velocity probe, the two or more temperature measurements including a first measurement obtained from the heated sensor and a second measurement obtained from the secondary temperature sensor;   calculate a mass flow rate using the first measurement and the second measurement, wherein the calculating is based on a computational model corresponding to a relationship of heat conduction and convection in the velocity probe relative to electrical power supplied to the heated sensor of the velocity probe, wherein the second measurement is used as a boundary condition in the computational model; and   output an output signal corresponding to the calculated mass flow rate.   
     
     
         2 . The computer readable medium of  claim 1 , further configured to cause the one or more processors to receive a third temperature measurement and use the third temperature measurement during said calculating of the mass flow rate. 
     
     
         3 . The computer readable medium of  claim 2 , wherein the third temperature measurement is obtained from a temperature sensor located adjacent to an end of the heated sensor opposite the secondary temperature sensor and is used as a as a second boundary condition during said calculating of the mass flow rate. 
     
     
         4 . The computer readable medium of  claim 2 , wherein the third temperature measurement is obtained from one or more temperature sensors located in a temperature probe spaced apart from the velocity probe. 
     
     
         5 . The computer readable medium of  claim 1 , further configured to cause the one or more processors to display the output signal in real time. 
     
     
         6 . A method of calculating mass flow rate of a fluid, comprising:
 receiving, in one or more processors, one or more signals corresponding to first and second temperature measurements obtained using a velocity probe immersed in a fluid, the velocity probe including a heated sensor for the first temperature and a secondary temperature sensor for the second temperature and spaced apart from the heated sensor by a distance no greater than three times a diameter of the velocity probe;   calculating, with the one or more processors, a mass flow rate of the fluid using the first and second temperature measurements, wherein the second temperature measurement is used as a boundary condition in a computational model corresponding to a relationship of heat conduction and convection in the velocity probe relative to electrical power supplied to the heated sensor of the velocity probe; and   outputting a signal corresponding to the mass flow rate of the fluid.   
     
     
         7 . The method of  claim 6 , wherein the outputting includes continuously outputting a calculated mass flow rate about once every second. 
     
     
         8 . The method of  claim 6 , further comprising receiving a third measurement from a distal temperature sensor located adjacent to the heated sensor opposite the secondary temperature sensor, and using the third measurement as a second boundary condition to the computational model.