Instruments for accurate measurement of air temperature and relative humidity in severe outdoor environments. On models DMA975 (Temp & Hum) (MTI.AWS.LS.975), an high efficiency natural ventilation radiant screen (with special black painting on the lower sur- face of the plates) ensures that the sensing element is protected by sun rays for accurate air temperature readings. For even better results in low wind and high solar radiation conditions, model DMA867 is equipped with a forced ventilation screen. Output of the models DMA975 is RS485 using Modbus RTU® or TTY-ASCII protocols. EXP815 model is equipped with an internal radio to send measurement up to 600 m far to data logger equipped with radio receiver.