How to calculate enthalpy and wet bulb temperature in T3 controller

All our temp and humidity sensors have the calculations on board so you can read enthalpy and wet bulb directly. I guess we should include some commands so that you can do it without using one of our sensors. Its on the todo list.

I am not sure if the Temco controls have an arc tangent function. If they do you can probably implement the Stull Wet-Bulb equation.
The Stull equation calculates wet bulb from relative humidity and the dry bulb temperature.

The equation is valid for relative humidities between 5% and 99% and for air temperatures between -20C and 50C, except for situations having both low humidity and cold temperature. Over the valid range, errors in wet-bulb temperature range from -2C to +0.65C, with mean absolute error of less than 0.3C.



I have successfully implemented this on an Allen-Bradley Micro820 PLC.

We don’t have the arc tan function unfortunately but I can promise our team will get an enthalpy function going in the T3 series very shortly. This is on the hotlist as soon as we get things settled down from the migration to a new CPU. The chip shortage forced us to move to a new chip and the port is nearly done. The good news is this new CPU has a ton more resources for adding more commands and features.