The Optidew 401 and Optidew 501 are fast-responding chilled mirror hygrometers utilizing the latest developments in chilled mirror technology. Ideal for use in industrial humidity control and precision laboratory applications. Available in bench top and wall mount configurations as well as a transmitter version of the Optidew 501 (without a display). Featuring ±0.15 °C accuracy across its -40 to +120 °C dew-point measurement range.