Accurate humidity measurements are becoming increasingly important, especially in regards to energy savings, indoor air quality and environmental protection. The Edgetech Instruments Model 645 offers the new modular system approach allowing you to purchase the instrument that currently meets your requirements, yet upgrade at a later time to meet your future measuring needs. Our modular design allows for easy upgrades to the instrument as they are developed, this way you will always have a measuring instrument corresponding to the latest technology. Model 645 incorporates a1% maintenance free humidity probe ideal for checking humidity measurements for validation of critical environments. The hygrometer is rugged, compact and protected by a waterproof plastic housing. The humidity measuring range is 0-100%RH with an accuracy of ±1%RH 10-90%, ±2% remaining range. The accuracy of this probe has been tested and proven time and again in worldwide laboratory tests. The probe is equipped with a patented %RH sensor.