Ratio

The function block has the input pins x, x1, y1, x2, and y2, and the output pin is OUTPUT. This function converts the input X to the output Y based on the line defined by x1, y1, x2, and y2. In case, if x1 and x2 are equal then OUTPUT will be y1.

The operation selection determines how the output is computed based on the line defined by x1, x2, y1, y2.

1. Unlimited

 

OUTPUT = y1 + (((x - x1) * (y2 - y1)) / (x2 - x1))

2. VAV Flow Balance

 

When x1 = 0, OUTPUT = 0

When x >= x1, OUTPUT = y1 + (((x - x1) * (y2 - y1)) / (x2 - x1))

When x < x1, OUTPUT = ((x * y2) / x2)

3. Endpoint Limited

Beyond points x1 and x2, the output is limited to the points y1 and y2 respectively. The Output is held between the points y1 and y2.

 

When x1 < x2 and x <= x1 OUTPUT = Y1

When x1 < x2 and x >= x2 OUTPUT = Y2

When x1 > x2 and x <= x2 OUTPUT = Y2

When x1 > x2 and x >= x1 OUTPUT = Y1

Inputs and Outputs

Analog Inputs

  Range    
Input Name Low High Input Value Description
x >=- infinity <+ infinity unconnected output set to invalid
      invalid output set to invalid
x1-2 >=- infinity <+ infinity unconnected output set to invalid
      invalid output set to invalid
      x1=x2 output set to y1
y1-2 >=- infinity <+ infinity unconnected output set to invalid
      invalid output set to invalid

Output

Output Name Range Description
OUTPUT Any floating point value Out Ratio (X, X1,Y1, X2,Y2)

Setpoint

Output Name Range/Value
Operation
  • Unlimited
  • Vav_Flow_Balance
  • Endpoint_Limited