====== Equithermal Curve - Using Four Points ======

{{:cs:mervis-ide:35-help:equithermalcurve4point.png}}

==== Full Name ====

Lib.Mervis.v1_0.EquithermalCurve4Point

==== Required Project References ====

  * Lib.Mervis

===== Description =====

A block for calculating the heating medium temperature according to an equithermal curve defined by four points.

===== Usage in ST =====

<code>
program test
    var
        eq4p: lib.mervis.v1_0.EquithermalCurve4Point;
    end_var

    eq4p();
end_program
</code>

===== Inputs =====

|Name |Data Type|Retain|Mandatory Connection|Meaning|
|In   |real     |No    |Yes                 |Outdoor temperature|
|X1   |real     |Yes   |No                  |First point of the curve - outdoor temperature|
|Y1   |real     |Yes   |No                  |First point of the curve - heating medium temperature|
|X2   |real     |Yes   |No                  |Second point of the curve - outdoor temperature|
|Y2   |real     |Yes   |No                  |Second point of the curve - heating medium temperature|
|X3   |real     |Yes   |No                  |Third point of the curve - outdoor temperature|
|Y3   |real     |Yes   |No                  |Third point of the curve - heating medium temperature|
|X4   |real     |Yes   |No                  |Fourth point of the curve - outdoor temperature|
|Y4   |real     |Yes   |No                  |Fourth point of the curve - heating medium temperature|
|DY   |real     |Yes   |No                  |Offset for the heating medium temperature|

===== Outputs =====

|Name |Data Type|Meaning|
|Out  |real     |Calculated heating medium temperature|

===== Detailed Function Description =====

{{:cs:mervis-ide:35-help:equithermalcurve4point_graph.png}}

The block calculates the heating medium temperature based on the outdoor temperature. The equithermal curve is defined by four points, with the condition that X1 < X2 < X3 < X4 must be satisfied for proper operation.