How do I Change the Temperature Units of Measure, WS-117x Series
To change the temperature Units of measure between degrees Celsius and degrees Fahrenheit, enter the SET mode.
To enter the SET mode, press and hold the SET button for 3 seconds.
See the table below. Press the SET button (do not hold) until the temperature units of measure is flashing. Press the + button to toggle between degC and degF. It is the ninth setting: