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

Claim 0:
1. A system for dividing a mass flow into secondary flows comprising:
an inlet configured to receive an inlet flow;
secondary flow lines connected to the inlet, each secondary flow line including:
a flow path configured to carry a secondary flow from the inlet 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

a controller configured to calculate a secondary flow rate of each secondary flow line based upon the pressure signal and the differential pressure signal and further configured to generate the control signal to each valve to obtain a desired ratio of secondary flow rate to total flow rate, wherein the controller is configured to compute and control 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.