The Extech RH490 hygro-thermometer is a precision instrument specifically designed for HVAC and water damage restoration contractors. It features a fast 30-second response time and ±2% accuracy. The dual backlit display simultaneously shows humidity or water vapor in grains per pound (g/kg) along with temperature, dew point, or wet bulb.

Key specifications: humidity range 0–100% RH, absolute humidity 0–1120 GPP (0–160 g/kg), temperature range -22 to 199°F (-30 to 100°C), dew point -22 to 199°F, wet bulb 32 to 176°F. Basic accuracy: ±2% RH, ±1.8°F/1°C. Resolution: 0.1% RH, 0.1°F/°C. The slim handheld design features rubberized sides for better grip and one-hand operation. Additional functions include data hold, min/max, auto power off with disable, and low battery indicator.