#### Issue

How is Enthalpy calculated in Sigma?

#### Product Line

Satchwell Sigma

#### Environment

Programmable Object

Prog Point

Enthalpy

#### Cause

Customers request for this information.

#### Resolution

A Programmable Object calculates Enthalpy using the following formula.

I = 1.006 * t + x * (2501 + 1.8 * t) where

t is the temperature and

x = 0.62198 * (í * pdm / (p - í * pdm)) and at p = 101.325 kPa =>

x = 0.62198 * (í * pdm / (101.325 - í * pdm))

where í is relative humidity and

pdm = p` = 101325 * 10A where

A = A0 - A1/T - A2*logT - A3*10(-T/A4) + A5*10(A6/T) where

A0 = 20.82648355

A1 = 2948.997118

A2 = 5.02808

A3 = 29811.33781

A4 = 32.923061

A5 = 25.21934913

A6 = 1302.8503

T = absolute temperature = 273.15 + t