Patent ID: 11940307
Assignee: MKS INSTRUMENTS, INC.
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 9:
10. A method of dividing a mass flow into secondary flows of desired ratios comprising:
receiving an inlet flow at an inlet;
dividing the inlet flow into secondary flow lines connected to the inlet, each secondary flow line including:
a flow path configured to carry a secondary flow with a secondary flow rate;
a pressure drop element in the flow path;
a valve configured to control the secondary flow rate based upon a control signal;
a pressure sensor upstream of the pressure drop element configured to provide a pressure signal representative of pressure at the pressure drop element; and
a differential pressure sensing element in communication with pressures upstream and downstream of the pressure drop element and configured to provide a differential pressure signal representative of differential pressure across the pressure drop element; and

determining, by a controller, the secondary flow rate of each secondary flow line based upon the pressure signal and the differential pressure signal; and
by the controller, generating and applying the control signal to each valve to obtain a desired ratio of secondary flow rate to total flow rate, wherein the controller computes and controls the ratio of each secondary flow rate according to the relationship, r
    i
   
   =
   
    
     
      Q
      i
     
     
      Q
      t
     
    
    =
    
     
      
       Q
       i
      
      
       
        
         ∑
          
        
        
         j
         =
         1
        
        N
       
       ⁢
       
        Q
        j
       
      
     
     =
     
      
       
        k
        i
       
       ·
       
        (
        
         
          2
          ⁢
          
           P
           
            u
            ,
            i
           
          
         
         -
         
          DP
          i
         
        
        )
       
       ·
       
        DP
        i
       
      
      
       
        
         ∑
          
        
        
         j
         =
         1
        
        N
       
       ⁢
       
        
         k
         j
        
        ·
        
         (
         
          
           2
           ⁢
           
            P
            
             u
             ,
             j
            
           
          
          -
          
           DP
           j
          
         
         )
        
        ·
        
         DP
         j
        
       
      
     
    
   
  
  ,
  
   i
   =
   1
  
  ,
  2
  ,
  
   …
   ⁢
     
   
    N
    .
   
  
 

wherein ri is the ratio between each secondary flow rate Q and the inlet flow rate Qt, k is a constant, Pu is the pressure signal representative of pressure at the pressure drop element, and DP is differential pressure signal representative of differential pressure across the pressure drop element.