Patent ID: 11940337
Assignee: SHENZHEN NEW DEGREE TECHNOLOGY CO., LTD.
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 12:
13. A pressure sensing method, performed by a pressure sensing device comprising:
a substrate attached to an object being tested, and p1 a pressure sensor, provided on the substrate, and comprising at least one thin-film piezoresistive sensor and at least four signal wires respectively led out from four corners of the thin-film piezoresistive sensor;
wherein a side of the thin-film piezoresistive sensor is attached to the substrate, and resistivity distribution of the thin-film piezoresistive sensor changes with deformation of the substrate when the substrate deforms, wherein one opposing pair of the at least four signal wires comprises one power wire and one ground wire respectively, and another opposing pair of the at least four signal wires comprises two differential wires; wherein the substrate is in a long strip shape, the long stripe-shaped substrate has two outer edges and two inner edges located inside the two outer edges, the thin-film piezoresistive sensor of the pressure sensor, the at least four signal wires and bonding pads at ends of the at least four wires are located within an area between the two inner edges; wherein one of sides of the thin-film piezoresistive sensor is parallel to an arrangement direction of the pressure sensor, and longitudinal directions of the at least four signal wires are parallel to the arrangement direction of the pressure sensor;
wherein the method comprises;
attaching the substrate to the object being tested;
making the thin-film piezoresistive sensor equivalent to a first equivalent circuit, wherein the first equivalent circuit comprises a bridge circuit provided with two pairs of bridge arms, a first resistor connected between the two differential wires, and a second resistor connected between the power wire and the ground wire, two ends of the bridge circuit are respectively connected to the power wire and the ground wire, and another two ends of the bridge circuit are respectively connected to the two differential wires;
deleting the second resistor, to obtain a second equivalent circuit, wherein the second equivalent circuit comprises a bridge circuit provided with two pairs of bridge arms, and a first resistor connected between the two differential wires, wherein two ends of the bridge circuit are respectively connected to the power wire and the ground wire, and another two ends of the bridge circuit are respectively connected to the two differential wires;
making a triangle-shaped circuit composed of the first resistor and the two pairs of bridge arms connected to the power wire in the second equivalent circuit equivalent to a Y-shaped circuit to obtain a third equivalent circuit;
obtaining a voltage a center point of the Y-shaped circuit and a voltage of the two differential wires according to Kirchhoff's law; obtaining a voltage drop between the two differential wires; obtaining deformation of the substrate through conversion of the voltage drop, and obtaining a pressure on the object being tested through conversion;
wherein in the first equivalent circuit, regarding the two pairs of bridge arms of the bridge circuit, one pair of the bridge arms are denoted as Rf1 and Rf2, and another pair of the bridge arms are denoted as Rm1 and and Rm2, the first resistor is denoted as Rx, and the second resistor is denoted as Ry; longitudinal directions of the bridge arms Rm1 and Rm2 are parallel to an arrangement direction of the pressure sensor, and longitudinal directions of the bridge arms Rf1 and Rf2 are perpendicular to the arrangement direction of the pressure sensor;
wherein three equivalent resistors of the Y-shaped circuit in the third equivalent circuit are denoted as Ra, Rb, and Rc respectively;, Ra
      =
      
        
          
            Rf
            ⁢
            1
          
          *
          
            Rm
            ⁢
            2
          
        
        
          
            Rf
            ⁢
            1
          
          +
          
            Rm
            ⁢
            2
          
          +
          Rx
        
      
    
    ;
  

  
    
      Rb
      =
      
        
          
            Rf
            ⁢
            1
          
          *
          Rx
        
        
          
            Rf
            ⁢
            1
          
          +
          
            Rm
            ⁢
            2
          
          +
          Rx
        
      
    
    ;
  

  
    
      Rc
      =
      
        
          
            Rm
            ⁢
            2
          
          *
          Rx
        
        
          
            Rf
            ⁢
            1
          
          +
          
            Rm
            ⁢
            2
          
          +
          Rx
        
      
    
    ;, the voltage at the center point of the Y-shaped circuit is calculated by:, VS
    =
    
      VCC
      *
      
        
          
            
              (
              
                Rb
                +
                
                  Rm
                  ⁢
                  1
                
              
              )
            
            ⁢
            
              (
              
                Rc
                +
                
                  Rf
                  ⁢
                  2
                
              
              )
            
          
          
            Rb
            +
            
              Rm
              ⁢
              1
            
            +
            Rc
            +
            
              Rf
              ⁢
              2
            
          
        
        
          Ra
          +
          
            
              
                (
                
                  Rb
                  +
                  
                    Rm
                    ⁢
                    1
                  
                
                )
              
              ⁢
              
                (
                
                  Rc
                  +
                  
                    Rf
                    ⁢
                    2
                  
                
                )
              
            
            
              Rb
              +
              
                Rm
                ⁢
                1
              
              +
              Rc
              +
              
                Rf
                ⁢
                2
              
            
          
        
      
    
  
  ;, the voltage of one of the differential wires is calculated by:, Vm
    +=
    
      
        V
        ⁢
        S
        *
        R
        ⁢
        m
        ⁢
        1
      
      
        
          R
          ⁢
          b
        
        +
        
          R
          ⁢
          m
          ⁢
          1
        
      
    
  
  ;, the voltage of another one of the differential wires is calculated by:, Vm
    -=
    
      
        V
        ⁢
        S
        *
        R
        ⁢
        f
        ⁢
        2
      
      
        
          R
          ⁢
          c
        
        +
        
          R
          ⁢
          f
          ⁢
          2
        
      
    
  
  ;, and the voltage drop between the two differential wires is calculated by:, Δ
    ⁢
    V
  
  =
  
    
      
        (
        
          Vm
          +
        
        )
      
      -
      
        (
        
          Vm
          -
        
        )
      
    
    =
    
      
        
          
            (
            
              
                Rm
                ⁢
                1
                ⁢
                Rm
                ⁢
                2
              
              -
              
                Rf
                ⁢
                1
                ⁢
                Rf
                ⁢
                2
              
            
            )
          
          ⁢
          Rx
          *
          VCC
        
        
          
            
              
                
                  Rm
                  ⁢
                  1
                  ⁢
                  Rm
                  ⁢
                  2
                  ⁢
                  Rx
                
                +
                
                  
                    Rf
                    ⁢
                    1
                    ⁢
                    Rm
                    ⁢
                    2
                  
                  ⁡
                  
                    (
                    
                      
                        Rm
                        ⁢
                        1
                      
                      +
                      Rx
                    
                    )
                  
                
                +
              
            
          
          
            
              
                
                  
                    Rf
                    ⁢
                    2
                    ⁢
                    Rm
                    ⁢
                    1
                  
                  ⁡
                  
                    (
                    
                      
                        Rm
                        ⁢
                        2
                      
                      +
                      Rx
                    
                    )
                  
                
                +
              
            
          
          
            
              
                
                  Rf
                  ⁢
                  1
                  ⁢
                  Rf
                  ⁢
                  2
                
                ⁡
                
                  (
                  
                    
                      Rm
                      ⁢
                      1
                    
                    +
                    
                      Rm
                      ⁢
                      2
                    
                    +
                    Rx
                  
                  )
                
              
            
          
        
      
      .