I have outdoor temperature and relative humidity transmitters that are inputs in a Controllogix PLC. I need Wet Bulb Temperature to determine how to control Cooling Tower/ heat exchanger bypass valves. Ranges: Temp -20 to 120 deg F RH = 0 to 100% Does Anyone know the formula for calculating Wet Bulb Temp. from Dry Bulb Temp. and Relative Humidity???