Extech RH390 Precision Psychrometer

The RH390 is engineered for professionals needing dependable, real-time environmental data. At its core is a precision capacitive humidity sensor paired with a thermistor, enabling relative humidity readings from 0 % to 100 % and ambient air temperature readings from –30 °C to 100 °C (–22 °F to 199 °F). From those primary measurements, the device internally computes dew point and wet-bulb temperatures, allowing users to assess moisture conditions and saturation behavior. The dual backlit LCD displays two parameters at once (for example, humidity + temperature, humidity + dew point, or humidity + wet-bulb), and users can toggle views easily. The RH390 offers fast response to changes (less than 30 seconds to 90 % of final value in moving air), and includes convenient features like Data Hold, Min/Max recording, auto power-off (with the option to disable), and a low battery indicator. Its slender, ergonomic housing with rubber-side grip ensures comfortable one-handed use. The unit ships complete with a carrying case and a 9 V battery, making it ready for field deployment.

Features

• ±2 % RH accuracy (in the 20–90 % RH range)
• Dual backlit display (showing humidity + one other parameter)
• Fast RH response: < 30 s to 90 % of final value in moving air
• Simultaneous display modes: Humidity/Temperature, Humidity/Dew Point, Humidity/Wet Bulb
• Data Hold, Min/Max recording
• Auto power-off (with disable) and low battery alert
• Slim, ergonomic design with rubberized grip for one-hand use
• Measurement ranges: RH 0–100 %; temperature –30 °C to 100 °C (–22 to 199 °F)
• Computed dew point (–30 °C to 100 °C) and wet-bulb temperature (0 to 80 °C)
• Portable kit includes carrying case and 9 V battery

Includes

• Carrying case
• 9V battery