Voltcraft pl 100trh thermo hygrometer voltcraft pl 100trh the voltcraft pl 100trh thermo hygrometer is a compact handheld meter for measuring air temperature and relative humidity both readings are shown simultaneously on the display with the included k type temperature sensor both indoor climate controls and material controls can be checked and verified it has min max and hold functions as well as the option to switch between fahrenheit and centigrade it has a built in ntc temperature